[Designation of Document] SPECIFICATION
[Title of the hivention] SURFACE-TREATED STEEL SHEET AND METHOD OF
MANUFACTURING THE SAME
[Technical Field]
[0001]
The present invention relates to a surface-treated steel sheet having excellent
corrosion resistance and painting adhesion and a method of manufacturing the same.
Eriority-4s ^ claimed onJapanese Patent Application No. 2011 -072926, filed on
March 29, 2011 and the content of which is incorporated herein by reference.
[Background Art]
[0002]
Hitherto, in various fields including household appliances, building materials,
vehicles, and the like, surface-treated steel sheets (electrogalvanized steel sheets)
having electrogalvanized layers have been used. In recent years, there is a demand
for fiirther enhancement in corrosion resistance for an electrogalvanized steel sheet.
As a method of enhancing corrosion resistance of the electrogalvanized steel
sheet, increasing the coating amount (coating weight) of a zinc-coated layer has been
considered. However, in a case where the coating weight of the zinc-coated layer is
increased, manufacturing cost is increased, and workability or weldability is degraded.
[0003]
As a method of enhancing the corrosion resistance or appearence of an
electrogalvanized steel sheet, a technique of forming a painted film on the surface has
been widely used hitherto (for example. Patent Document 1). However, when
adhesion (painting adhesion) between a coated layer and the painted film of the
electrogalvanized steel sheet is insufficient, even though the pamted film is formed on
the surface thereof, an effect of forming the painted film is not sufficiently obtained.
Therefore, enhancing painting adhesion as well as enhancing corrosion resistance of
the electrogalvanized steel sheet is required.
[0004]
In a case where the painted film is formed on the surface, increasmg the
thickness of the painted film is considered in order to enhance corrosion resistance.
However, since a conventional inorganic film containing a silane coupling agent and
the like, which has been widely employed as the painted film, does not contain a resin
component, it is difficult to increase the film thickness.
In addition, there is a demand for enhancing conductivity (hereinafter, referred
to as grounding properties) as well as corrosion resistance as described above for the
electrogalvanized steel sheet on which the painted film is formed. Although thiiming
the painted film is effective as measures of enhancing conductivity, when a thin film is
formed as described above, an enhancement of corrosion resistance cannot be achieved.
As described above, according to the related art, even when a film is further
formed on the surface of the electrogalvanized steel sheet, it is very difficult to satisfy
characteristics of both corrosion resistance and conductivity.
[0005]
In addition, in a case where a painted film is formed on the surface of a coated
layer having a high surface roughness, corrosion resistance is degraded. The
roughness of the coated layer is significantly dependent on the roughness of a steel
sheet before being subjected to coating. Therefore, in the electrogalvanized steel
sheet according to the related art, when the roughness of the steel sheet is high, the
roughness of the coated layer is necessarily increased, resulting in a deterioration of
corrosion resistance. In order to prevent the deterioration of corrosion resistance.
reducing the roughness of the coated layer in order to improve the roughness of the
steel sheet is considered. However, this is not preferable in terms of manufacturing
cost. Therefore, recently, there is a demand for enhancing corrosion resistance
without dependence on the roughness of a steel sheet.
[0006]
]n addition, in recent years, there is a surface-treated steel sheet on which a
chemical conversion treatment layer is formed by performing a chemical conversion
treatment on the surface of a metal sheet and a painted film is formed by applying a
paint onto a chemical conversion treatment layer. However, it is difficult to enhance
corrosion resistance while ensuring workability even with this painted film.
[0007]
Regarding the above described, in recent years, enhancing corrosion
resistance by containing a vanadium element into a zinc-coated layer of a surfacetreated
steel sheet subjected to electrogalvanizing has been examined. For example,
in Non-Patent Documents 1 to 4, techniques of causing the surface of a copper sheet as
a cathode to have complex electro deposition of a Zn-V oxide are described.
[0008]
However, in a case where a coated layer containing zinc and oxides of
vanadium is formed on the surface of a steel sheet by an electro coating method using
the techniques described in Non-Patent Documents 1 to 4, cracks are likely to occur on
the surface of the coated layer. When cracks are formed on the surface of the coated
layer, a surface-treated steel sheet having sufficient corrosion resistance is not obtained.
[Prior Art Document]
[Patent Document]
[0009]
- 3
[Patent Document 1] International Publication No. WO2010/137726
[Non-Patent Document]
[0010]
[Non-Patent Document 1] CAMP-ISU, Vol. 22 (2009), p.933 to 936
[Non-Patent Document 2] The kon and Steel Vol. 93 (2007), No. 11, p.49 -
54
[Non-Patent Document 3] The Abstract of 11S"" Lecture Conference of The
Surface Finishing Society of Japan, 9A-26, p. 139 to 140
[Non-Patent Document 4] Ferrum Vol. 13, No. 4, p.245,2008.4.1
[Disclosure of the Invention]
[Problems to be Solved by the Invention]
[0011]
The present invention has been made taking the foregoing circumstances into
consideration. That is, an object thereof is to provide a method of manufacturing a
surface-treated steel sheet (an electro coated steel sheet) in which, when a coated layer
that includes zinc and vanadium is formed on the surface of a steel sheet by an electro
coating method, cracks are less likely to be formed on the surface of the coated layer
and corrosion resistance and painting adhesion are excellent.
In addition, another object of the present invention is to provide a surfacetreated
steel sheet on which a coated layer that includes zinc and oxides of vanadium is
formed on the surface of a steel sheet and corrosion resistance and painting adhesion
are excellent.
[0012]
In addition, in the present invention, a surface-treated steel sheet on which one
or more layers of films are formed on the surface of a steel sheet (an electro coated
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steel sheet) having a coated layer that contains zinc and oxides of vanadium is further
examined.
[Means for Solving the Problems]
[0013]
In order to accomplish the objects, the inventors thoroughly researched the
following.
The inventors had focused on the adhesion amount (coating weight) of a
coated layer that contained zinc and vanadium and was formed on the surface of a steel
sheet by an electro coating method, the content of vanadium, and crystal structures,
and had examined the relationship between corrosion resistance and painting adhesion
of the coated layer obtained by causing the surface of the steel sheet to come into
contact with a coating bath using various methods.
[0014]
Specifically, as a method of causing the coating bath to come into contact with
the surface of the steel sheet as the cathode, a case where the steel sheet was dipped
into the coating bath in a stationary state in a coating tanlc (stationary state), a case
where the steel sheet was dipped into the coating bath in a stirred state of being stirred
by a stirrer disposed at the bottom portion of the coating tank (stirred state), and a case
where the steel sheet was dipped into a circulated coating bath and/or a coating bath
obtained by moving the steel sheet in the coating bath to cause the coating bath to be
fluidized relative to the steel sheet (fluidized state) were examined. The fluidized
state is different from the stirred state and the stationary state in that the coating bath is
fluidized at a substantially uniform flow rate with respect to the steel sheet.
[0015]
As a result of the examination, it was found that in a case where the coating
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bath in the fluidized state was caused to come into contact with the steel sheet and thus
a coated layer which sufficiently contained vanadium was formed, a plurality of
dendritic columnar crystals which were grown in the thickness direction of the steel
sheet were formed. In addition, in the present invention, the trunk portion of the
dendritic columnar crystal is referred to as a primary arm, the branch portion thereof is
referred to as a secondary arm, and the primary arms and the secondary arms are
collectively referred to as arms.
Moreover, as a result of examining the ratio of a content x of vanadium that
was present outside the arm to a content y of vanadium that was present inside the arm
in the coated layer, that is, x/y, it was found that the ratio was 1.1 or higher and 3.0 or
less in terms of vanadium element. In addition, the obtained coated layer was a
coated layer having a surface roughness of 1.0 |^m or higher and 4.0 fj,m or less, which
was a high roughness, in terms of center-line average roughness Ra.
Contrary to this, in the case where the surface of the steel sheet comes into
contact in the stationary state and the stirred state, a coated layer having dendritic
columnar crystals was not formed. Therefore, compared to the case where the
coating bath comes into contact with the steel sheet in the fluidized state, cracks were
likely to be generated on the surface of the coated layer.
[0016]
In the fluidized state, the coating bath was fluidized with respect to the steel
sheet at a substantially uniform flow rate. Therefore, compared to the stationary state
and the stirred state, ions were evenly and continuously supplied to the surface of the
steel sheet from the coating bath. As a result, it was presumed that a uniform coated
layer was formed on the surface of the steel sheet. Contrary to this, in the stationary
state and the stirred state, ions were locally and intensively consumed in the coating
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bath in the vicinity of the surface of the steel sheet as the cathode, and ions used for
deposition of the coated layer in the vicinity of the steel sheet were deficient.
Therefore, it was presumed that cracks were likely to occur.
[0017]
Furthermore, the inventors had examined the relationship between the content
of vanadium contained in the coated layer formed through an electro deposition by
causing a coating bath to come into contact with the surface of a steel sheet in the
fluidized state for a time of 1 second or longer and 30 seconds or less, the coating
weight of the coated layer, and the corrosion resistance of the surface-treated steel
sheet having the coated layer. As a result, it was found that when the surface-treated
steel sheet having the coated layer that contained zinc and vanadium formed by
causing the coating bath in the fluidized state to come into contact with the surface of
the steel sheet had a vanadium content of 1% or higher and 20% or less and a coating
weight of 3 g/m^ or higher and 40 g/m^ or less, sufficient corrosion resistance was
obtained.
[0018]
The inventors had examined adhesion (painting adhesion) between the coated
layer and a painted film by respectively applying a plurality of paints on the coated
layer which contained zinc and vanadium formed by causing the coating bath in the
fluidized state to come into contact with the surface of the steel sheet, and had a
vanadium content of 1% or higher and 20% or less and a coating weight of 3 g/m^ or
higher and 40 g/m^ or less.
As a result, it was found that the surface-treated steel sheet having the coated
layer had excellent painting adhesion compared to the electrogalvanized steel sheet
according to the related art.
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[0019]
• The inventors had examined painting adhesion and corrosion resistance by
forming a coated layer that contained zinc and vanadium in the same manner as the
case of the steel sheet using a copper sheet used as the cathode in Non-Patent
Documents 1 to 4 instead of a steel sheet. As a result, the coated layer formed on the
surface of the copper sheet could not obtain sufficient corrosion resistance in a case
where the vanadium content and the coating weight thereof were low. On the other
hand, in a case where a coated layer having a vanadium content of 3% or higher and a
coating weiglit of 3 g/m^ or higher was formed on the surface of the copper sheet in
order to ensure sufficient painting adhesion, the adhesion between the coated layer and
the copper sheet was insufficient. As such, it was difficult to form a coated layer
having sufficient corrosion resistance, excellent painting adhesion, and good adhesion
between the coated layer and the copper sheet, on the surface of the copper sheet.
[0020]
As described above, the inventors had formed the coated layer which
contained zinc and vanadium and had a vanadium content of 1% or higher and 20% or
less and a coating weight of 3 g/m^ or higher and 40 g/m^ or less on the steel sheet by
causing the coating bath in the fluidized state to come into contact with the surface of
the steel sheet through the electro coating method. The surface-treated steel sheet
having the coated layer was less likely to have cracks generated on the surface thereof
and had a plurality of dendritic columnar crystals that are grown in tlie thickness
direction of the steel sheet. Moreover, the ratio x/y of the content x of vanadium that
was present between the adjacent columnar crystals, that is, outside the arm to the
content y of vanadium that was present inside the columnar crystals, that is, inside the
arm was 1.1 or higher and 3.0 or less in terms of vanadium element, and corrosion
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resistance and painting adhesion were excellent.
[0021]
Next, a resin film was further formed on the surface of the coated layer having
excellent corrosion resistance and painting adhesion, and metal oxide particles and a
lubricant were added to the resin film as necessary to examine the corrosion resistance
of the resin film. As a result, it was found that even when the film was formed on the
coated layer having a high roughness, sufficient corrosion resistance was obtained
without deterioration of corrosion resistance.
Moreover, conductivity of the surface-treated steel sheet having the resin film
on the surface of the surface-treated steel sheet which had a coated layer with a high
roughness was examined. It was found that in a range in which the thickness of the
film is 0.5 to 5.0 |_im, sufficient conductivity was obtained without dependence on the
thickness of the film. That is, sufficient conductivity was provided naturally in a case
where the film was a thin film and even in a case of a thick film.
That is, it had been considered in the related art that providing a surfacetreated
steel sheet that satisfied both characteristics of corrosion resistance and
conductivity was very difficult. However, it was found that by forming the resin film
on the surface-treated steel sheet having the coated layer as described above, both
characteristics of corrosion resistance and conductivity could be enhanced.
[0022]
Furthermore, the inventors had examined, as in the above description,
corrosion resistance and conductivity on a surface-treated steel sheet in which a film
that contains an inhibitor obtained by applying a water-based metal surface treatment
agent whch includes a silane coupling agent onto the coated layer of the surface-treated
steel sheet having the above-described coated layer and drying the agent was formed to
have a total thickness of 0.5 to 4.0iim. As a result, it was found that sufficient
corrosion resistance was provided, and conductivity could be sufficiently ensured even
when the thickness of the film was thick.
Moreover, in the related art, it was difficult to obtain good workability
(working adhesion) even when a film was formed on the surface of a zinc-coated layer
that does not contain vanadium. However, it was found that in a case of a coated
layer containing vanadium, deterioration of working adhesion could be suppressed.
That is, it was found that characteristics of both corrosion resistance and conductivity
were compatible and excellent working adhesion could be ensured.
[0023]
In addition, the surface-treated steel sheet in which the coated layer that
contained zinc and oxides of vanadium was formed on the surface of the steel sheet as
described above exhibited a black appearence. However, for use as a design material
having the black appearence, there may be cases where fine unevenness of the
appearence on the coated surface has to be shielded, or in order to impart scratch
resistance needed for press working, a thick black film has to be further formed on the
coated layer.
[0024]
In such cases, in order to obtain a desired appearence, a thick film is further
formed on the coated layer. However, there may be cases where painting adhesion is
degraded while the working is in process, or a solvent in a paint bumps due to heating
in a process of drying the film and painting defects called popping occur.
Therefore, a steel sheet which has sufficiently suppressed glossiness, shields
the fine unevenness of the appearence of the coated surface, has a sufficiently low L*
value (brightness), has excellent scratch resistance and adhesion while the working is
- 10 -
in process, and has a more aesthetically pleasant appearence without forming a thick
black film on the upper surface of the coated layer that includes zinc and vanadium is
more valuable.
[0025]
For this, the inventors formed, on the coated layer of the surface-treated steel
sheet having the above-described coated layer, an organic resin film made of an
organic resin that includes a polyester resin (Al) containing a sulfonic acid group, a
curing agent (Bl), and a colorant (CI), and examined painting adhesion while the
working is in process, corrosion resistance, scratch resistance, glossiness, and L* value.
[0026]
As a result, since the coated layer contained zinc and vanadium in the coated
layer and had a plurality of dendritic columnar crystals that are grown in the thickness
direction of the sheet, the coated layer had an appearence with suppressed glossiness
and a low L* value. Moreover, excellent adhesion was obtained at the interface
between the coated layer and the organic resin film. Furthermore, regarding the
organic resin film, since the colorant (CI) that included a coloring pigment containing
carbon black was uniformly distributed in the organic resin fihn, an appearence having
sufficiently suppressed glossiness and a sufficiently low L* value was obtained even
when a thick film that degraded painting adhesion was not formed, and excellent
scratch resistance was obtained.
[0027]
The organic resin film is a dense film obtained by curing the polyester resin
(Al) containing the sulfonic acid group with the curing agent (Bl). Therefore, by
forming the organic resin film on the coated layer, a synergistic effect of excellent
corrosion resistance and paintLag adhesion caused by the coated layer and the effect of
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JUJk
enhancing corrosion resistance by the dense and thin organic resin film were obtained,
and thus the surface-treated steel sheet having very excellent corrosion resistance was
obtained.
[0028]
Moreover, the inventors formed, on one surface or both surfaces of the
surface-treated steel sheet having the coated layer, the coated layer that includes zinc
and vanadium and a colored painted film layer that includes a coloring pigment layer
in this order. As a result, the surface-treated steel sheet having excellent corrosion
resistance and workability was obtained.
[0029]
The present invention was completed on the basis of the above-described
knowledge.
In order to accomplish the objects by solving the problems, the present
invention employed the following measures.
(1) That is, a surface-treated steel sheet according to an aspect of the present
invention includes: a steel sheet; and a coated layer which is formed on one surface or
both surfaces of the steel sheet and includes zinc and vanadium, in which the coated
layer has a vanadium content of 1% or higher and 20% or less and a coating weight of
3 g/ra^ or higher and 40 g/m^ or less, and has a plurality of dendritic arms that are
grown in a thickness direction of the steel sheet, and a ratio x/y of a content x of the
vanadium that is present outside the arms to a content y of the vanadium that is present
inside the arms is 1.1 or higher and 3.0 or less in terms of vanadium element.
[0030]
(2) In the surface-treated steel sheet described in (1), the coated layer may
have an emissivity of 0.30 or higher and 0.95 or less in a region where a wave number
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measured under a condition of a surface temperature of 100°C is 600 to 3000 cm" .
[0031]
(3) In the surface-treated steel sheet described in (1) or (2), a surface
roughness of the coated layer may be 1.0 |im or higher and 4.0 |j.m or less in terms of
center-line average roughness Ra specified in JIS B 0601:2001.
[0032]
(4) hi the surface-treated steel sheet described in any of (1) to (3), one or more
layers of films may further be formed on the coated layer.
[0033]
(5) hi the surface-treated steel sheet described in (4), the film may contain an
organic resin.
[0034]
(6) In the surface-treated steel sheet described in (5), the film may be a resin
film, and may contain: 5 to 50 parts by mass of metal oxide particles with respect to
100 parts by mass of a solid content of the resin film; and 0.1 to 30 mass% of a
lubricant with respect to 100 mass% of the solid content of the resin film.
[0035]
(7) In the surface-treated steel sheet described in (5), the organic resin may
have at least one type of a carboxyl group, a hydroxyl group, a sulfonic acid group, and
a silanol group in its structure, and include: a polyester resin containing a sulfonic acid
group; a curing agent; and a coloring pigment containing carbon black.
[0036]
(8) In the surface-treated steel sheet described in (4), the film may be obtained
by applying and drying a water-based metal surface treatment agent containing a silane
coupling agent onto the steel sheet.
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[0037]
(9) In the surface-treated steel sheet described in (8), the film may fiarther
contain an inhibitor component which essentially includes a fluorometal complex
compound having at least one type selected fiom titanium and zirconium.
[0038]
(10) In the surface-treated steel sheet described in (8) or (9), the film may be a
composite film including: a polyether polyurethane resin; and a coloring pigment
containing carbon black.
[0039]
(11) In the surface-treated steel sheet described in (5), the film may be a
coloring painted film layer including a coloring pigment layer.
[0040]
(12) In the surface-treated steel sheet described in (11), the coloring painted
film layer may include a primer-painted film layer, and the primer-painted film layer
may be formed between the coated layer and the coloring pigment layer and includes a
rust-preventive agent.
[0041]
(13) In the surface-treated steel sheet described in (11) or (12), the coloring
painted film layer may be formed on the coated layer to be in contact therewith.
[0042]
(14) In the surface-treated steel sheet described in (11) or (12), a chemical
conversion treatment layer may further be included between the coloring painted film
layer and the coated layer.
[0043]
.-- (15) A method of manufacturing a surface-treated steel sheet according to ^
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another aspect of the present invention includes: a coating process of forming a coated
layer that includes zinc and vanadium on a surface of a steel sheet by an electro coating
method, in which, in the coating process, the coated layer is formed by dipping the
steel sheet in a coating bath, and performing an electro deposition at a current density
in the coating bath of 20 to 150 A/dm^ for a time of 1 second or longer and 30 seconds
or less, the coating bath contains a zinc compound and a vanadium compound,
contains at least one type of vanadium ions and vanadyl ions at a total content of 0.01
mol/1 or higher and less than 1.0 mol/1, and has a content of nitric acid ions limited to
be less than 0.0005 mol/1, and the coating bath is at least one of a circulated coating
bath or a coating bath obtained by moving the steel sheet in the coating bath to cause
the coating bath to be fluidized relative to the steel sheet, and the coated layer has a
vanadium content of 1% or higher and 20% or less and a coating weight of 3 g/m^ or
higher and 40 g/m^ or less.
[0044]
(16) In the method of manufacturing a surface-treated steel sheet described in
(15), an average flow rate of the coating bath in a coating tank may be in a range of 20
to 300 m/min.
[0045]
(17) In the method of manufacturing a surface-treated steel sheet described in
(15) or (16), the coating bath may include sodium ions at a content of 0.1 mol/1 or
higher and 4.0 mol/1 or less.
[0046]
(18) In the method of manufacturing a surface-treated steel sheet described in
any of (15) to (17), the coating bath may include nickel ions at a content of 0.01 mol/1
or higher and 1.0 mol/1 or Jess.
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i
[Advantage of the hivention]
[0047]
In the surface-treated steel sheet according to the aspects, the coated layer
which has a vanadium content of 1% or higher and 20% or less and a coating weight of
3 g/m^ or higher and 40 g/m^ or less, has a plurality of dendritic arms that are grown in
the thickness direction of the steel sheet, and has a ratio x/y of a content x of vanadium
that is present outside the arms to a content y of vanadium that is present inside the
arms of 1.1 or higher and 3.0 or less in terms of vanadium element. Therefore,
corrosion resistance and painting adhesion are excellent.
[0048]
In the method of manufacturing the surface-treated steel sheet according to
the aspects, in the coating process, the coated layer having a vanadium content of 1%
or higher and 20% or less and a coating weight of 3 g/m^ or higher and 40 g/m^ or less
is formed by dipping the steel sheet in the coating bath in the fluidized state and
perfonning electro deposition for a time of 1 second or longer and 30 seconds or less.
Accordingly, cracks are less likely to be generated on the surface of the coated layer,
and the coated layer having dendritic columnar crystals is obtained, thereby, the
surface-treated steel sheet with excellent corrosion resistance and painting adhesion are
obtained.
[0049]
Moreover, in the surface-treated steel sheet in which films such as the resin
film, the composite film, and the coloring painted film layer are further formed on the
coated layer, characteristics such as corrosion resistance, conductivity, and appearences
are more excellent.
[Brief Description of the Drawing] .
- 16 -
1^
[0050]
FIG. 1 is a schematic diagram illustrating an example of a coating apparatus
used in a method of manufacturing a surface-treated steel sheet according to this
embodiment.
FIG. 2 is a schematic diagram illustrating another example of the coating
apparatus used in the method of manufacturing a surface-treated steel sheet according
to this embodiment.
FIG. 3 A is a scanning electron micrograph of a coated layer of a surfacetreated
steel sheet of Example m23, and is a photograph in a view from the upper
surface side.
FIG. 3B is a scanning electron micrograph of the coated layer of the surfacetreated
steel sheet of Example m23, and is a photograph of the cross-section.
FIG. 4A is a scanning electron micrograph of a coated layer of a surfacetreated
steel sheet of Comparative Example x3, and is a photograph in a view from the
upper surface side.
FIG. 4B is a scanning electron micrograph of the coated layer of the surfacetreated
steel sheet of Comparative Example x3, and is a photograph of the crosssection.
FIG. 5 A is a scanning electron micrograph of a coated layer of an surfacetreated
copper sheet of Comparative Example x2, and is a photograph in a view from
the upper surface side.
FIG. 5B is a scanning electron micrograph of the coated layer of the surfacetreated
copper sheet of Comparative Example x2, and is a photograph of the crosssection.
FIG. 6A is a scanning electron micrograph of a coated layer of a surface-
- 17 -
$
treated steel sheet of Comparative Example xl, and is a photograph in a \iew from the
upper surface side.
FIG. 6B is a scaiming elecfron micrograph of the coated layer of the surfacetreated
steel sheet of Comparative Example xl, and is a photograph of the crosssection.
FIG. 7 is an enlarged cross-sectional view for explaining an example of a
surface-treated steel sheet according to a fifth embodiment.
FIG. 8 A is an enlarged cross-sectional view for explaining an example of the
surface-treated steel sheet according to a sixth embodiment.
FIG. 8B is an enlarged cross-sectional view for explaining the surface-treated
steel sheet according to a modified example of the sixth embodiment.
FIG. 8C is an enlarged cross-sectional view for explaining the surface-treated
steel sheet according to another modified example of the sixth embodiment.
FIG 9 is a schematic perspective view for explaining bending in a bending
workability test.
FIG. 10 is a schematic perspective view illustrating a cup-shaped molded body
in a drawing workability test.
[Embodiments of the Invention]
[0051]
Hereinafter, an embodiment to which the present invention is applied will be
described in detail with reference to the drawings.
[First Embodiment]
A case where a surface-treated steel sheet according to this embodiment is
manufactured by a method of manufacturing a surface-treated steel sheet according to
this embodiment by using a coating apparatus illustrated in Fig. 1 is exemplified.
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$
[0052]
FIG. 1 is a schematic diagram illustrating an example of the coatmg apparatus
used in the method of manufacturing a surface-treated steel sheet according to this
embodiment. In FIG. 1, reference numeral 1 denotes a steel sheet, reference numeral
2 denotes a coating bath, reference numeral 21 denotes a coating tank, and reference
numeral 3 denotes an anode.
The method of manufacturing the surface-treated steel sheet according to this
embodiment includes a coating process of forming a coated layer that includes zinc
and vanadium on the surface of the steel sheet 1 using an electro coating method.
[0053]
In this embodiment, the steel sheet 1 having the coated layer formed on the
surface is not particularly limited. For example, the steel sheet 1 may be a steel sheet
of any t)^e including a ultra low carbon type (a structure mainly containing ferrite), a
low carbon type (a structure including pearlite in ferrite), a dual phase structure type
(for example, a structure including martensite in ferrite and a structure including
bainite in ferrite), a strain induced transformation type (a structure including retained
austenite in ferrite), a microcrystal type (a structure mainly containing ferrite), and the
like.
[0054]
In FIG. 1, reference numerals 4 and 5 denote rolls which move the steel sheet
1 in a direction of the arrow in FIG. 1 to cause the steel sheet 1 to pass through the
coating bath 2. In this embodiment, among the rolls 4 and 5, the roll 4 disposed on
the upper portion of the steel sheet 1 fimctions as a connection member (conductor)
that electrically connects the steel sheet 1 to a power supply (not shown). The steel
sheet 1 is electrically connected to the roll 4 and acts as a cathode ^
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i$-
[0055]
In this embodiment, in the coating process, a coating tank 21 illustrated in FIG.
1 is used. The coating tank 21 has an upper tank 21a disposed on the upper portion of
the steel sheet 1 and a lower tank 21b disposed under the lower portion of the steel
sheet 1.
As illustrated in FIG. 1, at positions adjacent to the steel sheet 1 in the upper
tank 21a and the lower tank 21b, a plurality of anodes 3 made of platinum and the like
are arranged at predetermined intervals with the steel sheet 1 interposed therebetween.
The surface of each of the anodes 3 which opposes the steel sheet 1 is disposed to be
substantially parallel to the surface of the steel sheet 1. Each of the anodes 3 is
electrically connected to the power supply (not shown) by a connection member (not
shown).
[0056]
The upper tank 21a and the lower tank 21b are filled with the coating bath 2.
As illustrated in FIG. 1, between the upper tank 21a and the lower tank 21b of the
coating tank 21, the steel sheet 1 that is moved in a substantially horizontal surface
direction is disposed. The steel sheet 1 that is caused to pass through the coating tank
21 in the arrow direction (in the rightward direction in the figure) by the rolls 4 and 5 is
in a state of being dipped into the coating bath 2 in the upper tank 21a and the lower
tank 21b. Therefore, in this embodiment, since the steel sheet 1 is moved in the
coating bath 2 by moving the steel sheet 1 by the rolls 4 and 5, a fluidized state in
which the coating bath 2 is fluidized relative to the steel sheet 1 is achieved.
[0057]
As illustrated in FIG. 1, the upper tank 21a is provided with an upper supply
pipe 2a for supplying the coating bath 2 to the upper tank 21a so as to penetrate
- 20 -
through the upper surface of the upper tank 21a. The upper supply pipe 2a branches
off to a plurality of outer peripheral branch paths 2c and a plurality of intermediate
branch paths 2d (only one path is shown in FIG. 1) in the upper tank 21a. The
plurality of intermediate branch paths 2d are arranged along the width direction of the
steel sheet 1 between the adjacent anodes 3 in a plan view, and have opening portions
for supplying the coating bath 2 toward spaces between the both electrodes 3 (the
anodes) and the steel sheet 1. The plurality of outer peripheral branch paths 2c are
arranged along the width direction of the steel sheet 1 between the anodes 3 and the
rolls 4 in the plan view and have opening portions for supplying the coating bath 2
toward spaces between the electrodes 3 and the steel sheet 1.
[0058]
The upper tank 21a is provided with a discharge port (not shown) for
discharging the coating bath 2 and is connected to the upper supply pipe 2a via a pipe
(not shown) including a pump. Therefore, the coating bath 2 is supplied from the
upper supply pipe 2a to the upper tank 21a. Thereafter, the coating bath 2 is
discharged from the discharge port and is supplied from the upper supply pipe 2a again
by the pump via the pipe so as to be circulated.
[0059]
The lower tank 21b is provided with a lower supply pipe 2b for supplying the
coating bath 2 to the lower tank 21b to penetrate through the lower surface of the lower
tank 21b. The lower supply pipe 2b branches off to a plurality of outer peripheral
branch paths 2e and a plurality of intermediate branch paths 2f (only one path is shown
in FIG. 1) in the lower tank 21b. The plurality of intermediate branch paths 2f are
arranged along the width direction of the steel sheet 1 between the adjacent anodes 3 in
the plan view, and have opening portions for supplying the coating bath 2 toward
- 21 -
4
spaces between the electrodes 3 (the anodes) on both sides and the steel sheet 1. The
plurality of outer peripheral branch paths 2e are arranged along the width direction of
the steel sheet 1 between the anodes 3 and the rolls 5 in the plan view and have
opening portions for supplying the coating bath 2 toward spaces between the electrodes
3 and the steel sheet 1. .
[0060]
The lower tank 21b is provided with a discharge port (not shown) for
discharging the coating bath 2 and is connected to the lower supply pipe 2a via a pipe
(not shown) including a pump. Therefore, the coating bath 2 is supplied from the
lower supply pipe 2b to the lower tank 21b. Thereafter, the coating bath 2 is
discharged from the discharge port and is supplied from the lower supply pipe 2b again
by the pump via the pipe so as to be circulated.
[0061]
In the coating apparatus illustrated in FIG. 1, four electrodes 3 are arranged,
but the number of electrodes 3 may be any number. The number of electrodes 3 may
be appropriately determined depending on the sizes of the coating tank 21, the steel
sheet 1, and the electrodes 3, the arrangement of the upper supply pipe 2a and the
lower supply pipe 2b, the average flow rate of the coating bath 2 in the coating tank 21,
and the like. The arrangement and shapes of the upper supply pipe 2a and the lower
supply pipe 2b may be appropriately changed depending on the shape of the electrode
3, the average flow rate of the coating bath 2 in the coating tank 21, and the like.
[0062]
The coating process of this embodiment is a process of forming a coated layer
that includes zinc and vanadium by dipping the steel sheet 1 into the coating bath 2 in
the fluidized state in which the coating bath 2 is fluidized relative to the steel sheet 1
- 22 -
by setting the coating bath in the circulated and fluidized state and moving the steel
sheet 1 in the coating bath 2, and performing electro deposition thereon at a current
density in the coating bath of 20 to 150 A/dm^ for a time of 1 second or longer and 30
seconds or less.
In this embodiment, by performing the coating process, the coated layer
having dendritic columnar crystals (a primary arm and a secondary arm) with a
vanadium content of 1% or higher and 20% or less and a coating weight of 3 g/m^ or
higher and 40 g/m^ or less is formed on the surface of the steel sheet 1.
[0063]
In the coating process of this embodiment, the steel sheet 1 is dipped into the
coating bath 2 in the fluidized state in which the coating bath 2 is fluidized relative to
the steel sheet 1 by setting the coating bath 2 in the circulated and fluidized state and
causing the steel sheet 1 to pass through the coating bath 2. Therefore, ions are
sufficiently supplied between the steel sheet 1 and the electrodes 3. As a result, by
perfonning the coating process, a surface-treated steel sheet having the coated layer
which has a plurality of dendritic arms that are grown in the thickness direction of the
steel sheet and in which the ratio x/y of the content x of vanadium that is present
outside the arms to the content y of vanadium that is present inside the arms is 1.1 or
higher and 3.0 or less in terms of vanadium element is obtained.
[0064]
In this embodiment, in order to sufficiently and uniformly supply ions
between the steel sheet 1 and the electrodes 3, it is preferable that the steel sheet 1 is
dipped into the coating bath 2 in the fluidized state in which the coating bath 2 is
fluidized relative to the steel sheet 1 by setting the coating bath 2 in the circulated and
fluidized state as in the coating bath 2 of the coating tank 21 illustrated in FIG. 1 and
- 23
moving the steel sheet 1 in the coating bath 2. However, since the coating bath 2 of
the coating tank 21 illustrated in FIG. 1 is in the fluidized state in which the coating
bath 2 is fluidized relative to the steel sheet 1 by moving the steel sheet 1 in the coating
bath 2, ions can be suflFiciently supplied between the steel sheet 1 and the electrodes 3 .
even though the coating bath 2 is not circulated therein.
[0065]
In this embodiment, the surface-treated steel sheet in which the coated layer
formed by the coating process has a vanadium content of 1% or higher and 20% or less
and a coating weight of 3 g/m^ or higher and 40 g/m^ or less and has sufficient
corrosion resistance is obtained.
It is preferable that the vanadium content of the coated layer be 2% or higher
in order to further enhance corrosion resistance and painting adhesion. The vanadium
content of the coated layer is set to be 20% or less in order to obtain good adhesion
between the coated layer and the steel sheet 1, and is more preferably, 15% or less.
[0066]
Although the coating weight of the coated layer is 3 g/m^ or higher, in a case
of further enhancing corrosion resistance and painting adhesion, a coating weight of 5
g/m^ or higher is preferable. The coating weight of the coated layer is preferably 40
g/m^ or less and more preferably 15 g/m^ or less. In a case where the coating weight
of the coated layer is 40 g/m^ or less, the manufacturing cost is increased, and the
coating adhesion (powdering properties) is deteriorated. Moreover, in a case of 15
g/m^ or less, compared to electrogalvanizing (typically, about 20 g/m^) and the like
performed according to the related art, the amount of metal dpposited is low, and is
thus economically superior in terms of metal costs and power costs for forming coated
layers.
24
[0067]
The coated layer obtained in this embodiment exhibits a black appearence
since vanadium elements are dendritically present as oxides in zinc. Therefore, in a
case where the surface-treated steel sheet of this embodiment is used as a material of,
for example, a product having a black appearence, a desirable appearence is provided.
In addition, in a case where a painted film is applied to obtain the black appearence,
the thickness of the painted film can be reduced. In addition, the color of the coated
layer is darkened as the vanadium content is increased, and the L* value is reduced.
[0068]
In the coating process, the electro deposition time is set to 1 second or longer
in order to obtain a sufficient coating weight. On the other hand, from a viewpoint of
not harming productivity, the electro deposition time is set to 30 seconds or less, and
preferably, is set to 1 second or longer and 15 seconds or less.
In addition, in the coating process, the current density is set to 20 to 150
A/dm^. When the current density is in the above range, the coated layer of this
embodiment, which has a vanadium content of 1% or higher and 20% or less and a
coating weight of 3 g/m^ or higher and 40 g/m^ or less can be easily formed. When
the current density is less than 20 A/dm^, a predetermined vanadium content and/or
coating weight are difficult to be ensured. When the current density exceeds 150
A/dm^, there is a concern that adhesion between the coated layer and the steel sheet 1
may be degraded.
[0069]
In this embodiment, since the coated layer is formed by dipping the steel sheet
1 into the coating batli 2 in the fluidized state, in order to ensure a sufficiently high
vanadium content, the current density needs to be high compared to a case where the
25
coating bath is caused to come into contact with the surface of the steel sheet in the
stationary state and the stirred state. This is because, in the case where the steel sheet
1 is dipped into the coating bath 2 in the fluidized state, ions are uniformly and
continuously supplied to the surface of the steel sheet 1 from the coating bath 2, and
. thus the coated layer is difficult to incorporate vanadium compared to the case in the
stationary state and in the stirred state.
[0070]
In the coating process, the average flow rate of the coating bath 2 in the
coating tank 21 is preferably in a range of 20 to 300 m/min, and more preferably, in a
range of 40 to 200 m/min. In a case where the average flow rate of the coating batli 2
is in a range of 20 to 300 m/min, generation of cracks on the coated layer can be more
effectively prevented. When the average flow rate of the coating bath 2 is below the
above range, there is a concern that the effect caused by circulating the coating bath 2
to be in the fluidized state may become insufficient. In addition, when the average
flow rate of the coating bath 2 exceeds the above range, there is a concern that the
supply of ions to the surface of the steel sheet 1 from the coatmg bath 2 may be
disrupted.
[0071]
In the coating process, the coating bath 2 includes a V compound and a Zn
compound. To the coating bath 2, in addition to the V compound and the Zn
compound, as necessary, a pH adjusting agent such as H2SO4 or NaOH, metal
compounds other than the V compound and the Zn compound such as a Ni compound
including NiS04-6H20, and additives such as Na2S04 which stabilize the conductivity
of the coating bath 2 may be added. However, the content of nitric acid ions in the
coating bath 2 is limited to be less than 0.0005 mol/1 in .order to reliably generate
- 26 -
#
dendritic columnar crystals.
Examples of the Zn compound used in the coating bath 2 include metal Zn,
ZnS04-7H20, and ZnCOs. These may be used singly or in a combination of two or
more types thereof
Examples of the V compound used in the coating bath 2 include ammonium
metavanadate (V), potassium metavanadate (V), sodium metavanadate (V),
VO(C5H702)2 (vanadyl acetyl acetonate (IV)), and VOS04-5H20 (vanadyl sulfate (IV)).
These may be used singly or in a combination of two or more types thereof
[0072]
It is preferable that the coating bath 2 include Zn^"^ and VO^"^, or V"^ as the V
compound and the Zn compound.
In a case where the coating bath 2 includes any of or both VO^^ and V*"^, the
total content thereof in the coating bath 2 is 0.01 mol/1 or higher and 1.0 mol/1 or less.
By using the coating bath 2 that includes VO^* or V'"*^ in the above range, the coated
layer having a vanadium content of 1% or higher and 20% or less and a coating weight
of 3 g/m^ or higher and 40 g/m^ or less can be easily formed. In the case where the
content of VO^"*^ or V'*^ included in the coating bath 2 is below the above range, the
plurality of dendritic columnar crystals 12 are less likely to be grown in the thickness
direction of the steel sheet I, and thus the vanadium content is reduced. In addition,
when the content of VO^"^ or V*^ included in the coating bath 2 exceeds the above
range, a large amount of vanadium which is expensive is used in the coating bath 7,,
which is economically disadvantageous.
In a case where the coating bath 2 includes Zn^"^, the content of Zn^"*" is
preferably 0.1 to 1.5 mol/1 and more preferably 0.35 to 1.2 mol/1.
[0073]
27
In addition, it is preferable that 0.1 mol/1 or higher of sodium ions are
included in the coating bath 2. In this case, the conductivity of the coating bath 2 can
be increased, and thus the coated layer of this embodiment can be easily formed.
However, when the content thereof is 4.0 mol/1 or higher, sodium ions are excessively
included. In this case, sodium ions are not present while being dissolved in the
coating bath but are precipitated, that is not preferable.
In a case where the coating bath 2 includes the Ni compound, it is preferable
that 0.01 mol/1 or higher of nickel ions be included in the coating bath 2. In this case,
vanadium is likely to be deposited, and thus a coated layer of this embodiment can be
easily formed. However, it is not preferable that the content thereof is 1.0 mol/1 or
higher because there is a concern about deterioration of corrosion resistance or coating
adhesion of the surface-treated steel sheet.
[0074]
The temperature of the coating bath 2 is not particularly limited, and is
preferably in a range of 40 to 60°C in order to easily and efficiently form the coated
layer of this embodiment. In addition, the pH of the coating bath 2 is preferably in a
range of 1 to 5, and more preferably in a range of 1.5 to 4 in order to easily form the
coated layer of this embodiment having the dendritic columnar crystals, the above
vanadium content, and the coating weight.
[0075]
It is preferable that the surface roughness of the coated layer is preferably 1.0
|j.m or higher and 4.0 |a.m or less in terms of center-line average roughness Ra defined
in JIS B 0601:2001. According to the related art, it has been considered that
corrosion resistance is ensured by reducing the surface roughness of the coated layer.
However, in the present invention, since the coated layer has sufficient corrosion
- 28 -
resistance, even in a coated layer having a roughness Ra of 1.0 nm or higher, which is
a high roughness, corrosion resistance is not deteriorated. Moreover, since the
surface roughness of the coated layer is a high roughness, conductivity in a case where
a film is formed later can be ensured, and working adhesion can be enhanced. On the
other hand, the roughness Ra exceeds 4.0 i^m, rubber of a roll coater or a pass roll is
scraped off, and there is a concern that the scraped parts may stick to a product as
waste. Therefore, the upper limit is set to 4.0 i^m. In addition, more preferably, the
roughness is 1.1 pm or higher and 3.0 [im or less.
[0076]
The crystal structure of the coated layer of the surface-treated steel sheet
formed in this embodiment will be described using the drawings. FIGS. 3A and 3B
are scanning electron micrographs of the coated layer of an example of the surfacetreated
steel sheet according to this embodiment. FIG. 3A is a photograph viewed
from the upper surface side, and FIG. 3B is a photograph of the cross-section.
[0077]
As shown in FIGS. 3A and 3B, the coated layer 11 does not have cracks
(gaps) that reach the steel sheet 1 and has a plurality of fme and dense dendritic
columnar crystals 12 (arms) that are grown in the thickness direction of the steel sheet
1. Each of the columnar crystals 12 are grovm in the surface direction of the steel
sheet 1 as well as in the thickness direction from the surface of the steel sheet 1.
Therefore, at least a part of the columnar crystals 12 has a shape that is separated from
a base portion 12a that comes into contact with the steel sheet 1 and is integrated with
the adjacent columnar crystal 12 at a part 12b distant from the steel sheet 1 as shown in
FIG. 3B.
. [0078]
- 29 -
Between the adjacent columnar crystals 12, that is, inside the coated layer and
outside the arms, an area 13 having a larger content of vanadium (a dark gray part in
FIG. 3B) than the content of vanadium inside the columnar crystals 12, that is, inside
the arms (a light gray part in FIG. 3B) is formed so as to be fringed with the columnar
crystals 12. The ratio x/y of the content x of vanadium that is present outside the
arms to the content y of vanadium that is present inside the arms is 1.1 or higher in
terms of vanadium element. From a viewpoint of corrosion resistance, the ratio x/y is
more preferably 1.2 or higher. In a case where the x/y exceeds 3.0, V needs to be
excessively added, and thus high cost is needed, that is not preferable. In a case
where the ratio x/y is in a range of 1.2 to 2.0, better corrosion resistance is obtained at
low cost.
[0079]
The surface-treated steel sheet according to this embodiment has a plurality of
fine and dense dendritic columnar crystals 12 that are grown in the thickness direction
of the steel sheet 1 as shown in FIGS. 3 A and 3B. In addition, the coated layer 11 in
which at least a part of the columnar crystals 12 has a shape that is separated from the
base portion 12a and is integrated with the adjacent columnar crystal 12 at the part 12b
distant from the steel sheet 1 is formed, and thus excellent painting adhesion is
provided. It is presumed that this is because the columnar crystals 12 ftinction as the
anchor effect.
In this embodiment, as shown in FIGS. 3A and 3B, the area 13 which does not
have cracks (gaps) that reach the steel sheet 1 and has a larger content of vanadium
between the adjacent columnar crystals 12 (outside the arms) than the content of
vanadium inside the columnar crystals 12 (inside the arms) is formed. Therefore, it is
presumed that the effect of enhancing corrosion resistance by containing vanadium is
- 30 -
more effectively exhibited.
[0080]
In addition, in this embodiment, the coated layer 11 has a vanadium content of
1% or higher and 20% or less and a coating weight of 3 g/m^ or higher and 40 g/m^ or
less, and has a plurality of dendritic columnar crystals 12 that are grown in the
thickness direction of the steel sheet 1. The coated layer formed in this embodiment
has an emissivity of 0.30 or higher in a region in which the wave number measured at
I00°Cis600to3000cm-The emissivity becomes the same as the absorptance of an object at a
predetermined temperature, and increase in emissivity results in increase in thermal
absorptivity. The emissivity of the coated layer 11 is preferably 0.30 or higher, and
more preferably 0.60 Or higher in order to sufficiently obtain the thermal absorptivity
effect and a heat dissipation effect.
[0081]
In a case where the vanadium content of the coated layer 11 is less than 1% or
in a case where the coating weight thereof is less than 3 g/m^, the emissivity is more
likely to be less than 0.30. When the emissivity of the coated layer U is less than
0.30, there may be cases where the thermal absorptivity effect and the heat dissipation
effect are not sufficiently obtained.
In addition, absorption of radiations in a range in which the wave number is
less than 600 cm"^ or higher than 3000 cm"^ has a very small influence on the thermal
absorptivity of the surface-treated steel sheet and a very small effect in a temperature
reduction, and thus the emissivity including radiations in such a wave number range is
inappropriate. In addition, the temperature at which the emissivity is measured was
set to 100°C in consideration of operation temperatures of electronic circuits such as
- 31
IC chips used in electronic components.
[0082]
In the surface-treated steel sheet of this embodiment, the coated layer 11
having an emissivity of 0.30 or higher in a region in which the wave number measured
at 100°C is 600 to 3000 cm'^ is formed on the surface of the steel sheet 1. Therefore,
the surface-treated steel sheet can absorb more heat from the outside and efficiently
dissipate heat and thus can be appropriately used as, for example, a heat sink of an
electronic component.
[0083]
[Second Embodiment]
A surface-treated steel sheet and a method of manufacturing the same
according to a second embodiment will be described using a coating apparatus
illustrated in FIG. 2.
FIG. 2 is a schematic diagram illustrating another example of the coating
apparatus used in the method of manufacturing the surface-treated steel sheet
according to this embodiment. In FIG. 2, reference numeral 10 denotes a steel sheet,
reference numeral 32 denotes a coating bath, reference numeral 22 denotes a coating
tank, and reference numeral 23 denotes an anode.
[0084]
The steel sheet 10 illustrated in FIG. 2 has a plane shape smaller than the
plane shape of the coating tank 22. The steel sheet 10 is not particularly limited, and
may use those made of the same material as the steel sheet 1 used in the first
embodiment.
The coating bath 32 may use the same coating bath 2 used in the first
embodiment.
32
[0085]
In this embodiment, a coating process of forming a coated layer that includes
zinc and vanadium on the surface of the steel sheet 10 by an electro coating method
using the coating tank 22 illustrated in FIG. 2 is performed. A discharge port 32c is
provided in one side surface 32a of opposing side surfaces of the coating tank 22. A
supply port 32d is provided in the other side surface 32b. As illustrated in FIG. 2, the
discharge port 32c and the supply port 32d are connected by a pipe 32e, and a pump P
is connected to the pipe 32e.
As illustrated in FIG. 2, the anode 23 made of platinum and the like is
disposed at the bottom portion of the coating tank 22. The coating tank 22 is filled
with the coating bath 32, and the steel sheet 10 as the cathode is dipped into the coating
bath 32 substantially horizontally in the surface direction.
[0086]
The coating process of this embodiment, as illustrated in FIG 2, is a process of
forming a coated layer that includes zinc and vanadium by dipping the steel sheet 10
into the coating bath 32 in a fluidized state in which the coating bath 32 is discharged
from the discharge port 32c of the coating tank 22 and the coating bath 32 is supplied
from the supply port 32d by the pump P via the pipe 32e so as to be circulated.
Even in this embodiment, by performing the coating process, the coated layer
having dendritic columnar crystals with a vanadium content of 1% or higher and 20%
or less and a coating weight of 3 g/m^ or higher and 40 g/m^ or less is formed on the
surface of the steel sheet 10.
[0087]
In the coating process of this embodiment, since the steel sheet 10 is dipped
into the coating bath 32 in the circulated and fluidized state, ions are sufficiently
- 33 -
supplied between the steel sheet 10 and the electrode (anode) 23. As a result, by
performing the coating process, a surface-treated steel sheet having the coated layer
which has a plurality of dendritic arms (columnar crystals) that are grown in the
thickness direction of the steel sheet 10 and in which the ratio x/y of the content x of
vanadium that is present outside the arms (between the adjacent columnar crystals) to
the content y of vanadium that is present inside the arms (inside the columnar crystals)
is 1.1 or higher and 3.0 or less in terms of vanadium element is obtained.
[0088]
As in the first and second embodiment, in the case where the steel sheet is
dipped into the coating bath in the circulated and fluidized state, as in the coating bath
2 of the coating tank 21 of the first embodiment, the coating bath 2 may be in the
fluidized state of being fluidized relative to the steel sheet 1, or the steel sheet may not
be moved in the coating bath as in the second embodiment. In the second
embodiment, since the coating bath 32 is in the circulated and fluidized state, the
coating bath is fluidized relative to the steel sheet, and thus ions can be sufficiently
supplied between the steel sheet 10 and the electrode 23.
[0089]
Hereinafter, an example in which one or more layers of films are fiirther
formed on the upper surface of the coated layer of the surface-treated steel sheet
obtained in the first or second embodiment will be described in [Third Embodiment] to
[Sixth Embodiment].
[0090]
[Third Embodiment]
A surface-treated steel sheet obtained by forming a resin film on the surfacetreated
steel sheet having the coated layer that includes zinc and vanadium according
- 34 -
to the first or second embodiment will be described. In addition, there may be cases
where the resin film is referred to as a resin film according to this embodiment. In
addition, there may be cases where the coated layer included in the surface-treated
steel sheet used in this embodiment is referred to as a coated layer according to this
embodiment.
As the resin film (A) according to this embodiment, one or more layers of the
resin films (A) are formed on the upper surface of the coated layer according to this
embodiment. The thickness of at least one layer of the plurality of resin films (A) is
preferably 0.5 to 5.0 |Jin. According to the related art, it has been considered that a
reduction in the thickness of the film and an increase in the roughness of the coated
layer cause deterioration of corrosion resistance. However, as described above, since
the coated layer according to this embodiment has very high corrosion resistance, even
when the coated layer has a high roughness, sufficient corrosion resistance can be
ensured with the thickness of the films described above. Moreover, since the coated
layer according to this embodiment has a high roughness, sufficient conductivity can
be ensured with the thickness of the films described above. In terms of corrosion
resistance, the thickness of the resm fihns (A) is more preferably 0.5 [im or higher, and
even more preferably 1.0 )am or higher. In addition, in terms of conductivity, the
thickness of the resin films (A) is more preferably 5.0 ^m or less, and even more
preferably 4.0 |am or less.
[0091]
The resin film (A) is collectively referred to as, other than a water-soluble
resin, a resin (water-dispersible resin) which is not soluble in water and can be in a
state of being finely dispersed in water like an emulsion or a suspension.
[0092]
- 35 -
4
The type of the resin film (A) is not particularly limited. For example, at
least one or more types selected from the group consisting of a polyester-based resin, a
polyurethane resin, an acrylic resin, an epoxy-based resin, polyolefin, and modified
resins thereof
[0093]
The polyester-based resin is not particularly limited. For example, those
obtained by carrying out dehydration-condensation of polyols such as ethylene glycol,
propylene glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, triethylene
glycol, bisphenol hydroxypropyl ether, glycerin, trimethylol ethane, and trimethylol
propane and polybasic acid such as phthalic anhydride, isophthalic acid, terephthalic
acid, succinic anhydride, adipic acid, sebacic acid, maleic anhydride, itaconic acid,
fiimaric acid, and himic anhydride, and neutralizing the resultant with ammonia, an
amine compound, or the like, followed by dispersion in water can be used.
[0094]
The pol3airethane resin is not particularly limited. For example, those
obtained by causing polyols such as ethylene glycol, propylene glycol, diethylene
glycol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxypropyl
ether, glycerin, trimethylol ethane, and trimethylol propane to react with a diisocyanate
compound such as hexamethylene diisocyanate, isophorone diisocyanate, and tolylene
diisocyanate, and further chain-extending the resultant with diamine or the like,
followed by dispersion in water can be used.
[0095]
The acrylic resin is not particularly limited. For example, those obtained by
radical polymerization of unsaturated monomers such as styrene, alkyl(meth)acrylates,
(meth)acrylic acids, hydroxyalkyl(meth)acrylates, and alkoxysilane(meth)acrylates in
- -36 -
j ^
an aqueous solution using a polymerization initiator can be used. In addition, the
polymerization initiator is not particularly limited, and for example, persulfates such as
potassium persulfate and ammonium persulfate and an azo compound such as azobiscyanovaleric
acid and azobisisobutyronitrile can be used.
[0096]
The epoxy resin is not particularly limited. For example, those obtained by
causing epoxy resins such as bisphenol Atype epoxy resin, bisphenol F type epoxy
resin, resorcinol type epoxy resin, hydrogenated bisphenol Atype epoxy resin,
hydrogenated bisphenol F type epoxy resin, resorcinol type epoxy resin, and novolac
type epoxy resin to react with an amine compound such as diethanolamine andNmethylethanolamine,
and neutralizing the resultant with an organic acid or an inorganic
acid, or those obtained by carrying out radical polymerization of a high acid value
acrylic resin in the presence of the epoxy resins and thereafter neutralizing the resultant
with ammonia or an amine compound, followed by dispersion in water can be used.
[0097]
The polyolefm resin is not particularly limited. For example, those obtained
by carrying out radical polymerization of ethylene and unsaturated carboxylic acid
such as methacrylic acid, acrylic acid, maleic acid, fiimaric acid, itaconic acid, and
crotonic acid at a high temperature and a high pressure, and thereafter neutralizing the
resultant with ammonia or an amine compound, a metal compound such as KOH,
NaOH, and LiOH, an ammonia or an amine compound containing the metal compound,
or the like, followed by dispersion in water can be used.
[0098]
In addition, as types of the resin film (A), a phenol resin can be used.
In addition, the phenol resin is not particularly limited. For example, those
- 37
obtained by causing phenol resins such as a methylol phenol resin which is obtained by
an addition reaction of aromatics such as phenol, resorcin, cresol, bisphenol A, and
paraxylylene dimethyl ether and formaldehyde in the presence of a reaction catalyst to
react with an amine compound such as diethanolamine and N-methylethanolamine,
and neutralizing the resultant with an organic acid or an inorganic acid can be used.
[0099]
It is preferable that the resin film according to this embodiment contain metal
oxide particles and a lubricant. In this case, the content of the metal oxide particles
(B) is 5 to 50 mass% with respect to 100 mass% of the solid content of the resin film
(A). In a case where the content thereof is less than 5 mass%, an effect of enhancing
corrosion resistance is small. On the other hand, in a case of a content of higher than
50 mass%, a resin-based film becomes brittle, and the effect of enhancing corrosion
resistance of worked parts is small.
[0100]
The type of the metal oxide particles (B) is not particularly limited. For
example, particles made from at least one type of metal element selected fi-om the
group consisting of Si, Ti, Al, and Zr may be employed, and more specifically, silica
particles, titania particles, alumina particles, zirconia particles, and the like can be used.
As the metal oxide particles (B), particles having an average particle diameter of about
1 to 300 nm are appropriate. These may be used singly or in a combination of two or
more types thereof
[0101]
In addition, it is preferable that the content of the lubricant (H) is 0.1 to 30
mass% with respect to 100 mass% of the solid content of the resin film (A). In a case
where the content is less than 0.1%, an effect of enhancing workability is small, and in
- 38 -
the case of a content of higher than 30%, there may be cases where the effect of
enhancing corrosion resistance is not obtained.
[0102]
As the lubricant (H) is contained as described above, lubricity of the resinbased
film is enhanced. As a result, there are advantages in enhancement of
workability during press molding, prevention of scratches due to molds or handling,
and prevention of abrasion flaws during transportation of molded products or coils.
[0103]
The lubricant (H) is not particularly limited. Well-known fluorine-based,
hydrocarbon-based, fatty acid amide-based, ester-based, alcohol-based, metallic soapbased,
and inorganic lubricants and the like can be used. As the criteria of selection
of lubricating additives for enhancing workability, to select a material which is present
on the surface of the resin film rather than present while being dispersed in the resin
film formed by the added lubricant is effective in terms of reducing friction between
the surface of a molded article and a mold and maximizing the lubricating effect. In a
case where the lubricant is present while being dispersed in the formed resin film, poor
appearences called a powdering phenomenon in which the coefficient of surface
friction is high, the resin film is easily broken, and powdery materials are peeled and
deposited, and degradation in workability occurs. As the material that is present on
the surface of the resin film, a material that is not compatible with resins and has a low
surface energy is selected.
[0104]
A polyolefin wax is more preferably used as the lubricant (H) because the
coefficient of kinetic friction of the surface is reduced, workability is significantly
enhanced, and corrosion resistance after working is good. Examples of the wax
- 39 -
include a hydrocarbon-based wax such as paraffm, microcrystalline, or polyethylene.
In addition, while the working is in process, the temperature of the film is increased
due to the deformation heat and frictional heat of materials, and thus the melting point
of the wax is more preferably 70 to 160°C. When the melting point is less than 70°C,
there may be cases where the lubricant is softened and melted while the working is in
process and does not exhibit excellent characteristics as a lubricant. In addition,
when the melting point exceeds 160°C, hard particles are present on the surface and
degrade frictional characteristics, and thus there may be cases where high-degree
molding workability is not obtained.
[0105]
The particle diameter of the wax is more preferably 0.1 to 5 \xm. When the
particle diameter thereof exceeds 5 jxm, there is a possibility that distribution of the
solidified wax may become uneven or the wax may come away from the resin-based
film. In addition, in a case where the particle diameter thereof is less than 0.1 |a,m,
there may be cases where workability is insufficient.
[0106]
It is preferable that the resin film (A) according to this embodiment further
contain a phosphate compound (C). When the phosphate compound (C) is contained,
a phosphate layer is formed on the surface of the coated layer and is passivated,
resulting in enhancement in corrosion resistance.
[0107]
Examples of the phosphate compound (C) include phosphoric acid such as
orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid,
and tetraphosphoric acid, and salts thereof; phosphonic acid such as
aminotri(methylenephosphonic acid), l-hydroxyethylidene-l,l-diphosphonic acid,
- 40 -
ethylenediamine tetra(methylenephosphonic acid), and diethylene triamine
penta(methylenephosphonic acid), and salts thereof; and organophosphorus acid such
as phytic acid, and salts thereof The cationic types of salts are not particularly
limited, and examples thereof include Cu, Co, Fe, Mn, Sn, V, Mg, Ba, Al, Ca, Sr, Nb, Y,
Ni, and Zn. These may be used singly or in a combination of two or more types
thereof
[0108]
It is preferable that 0.01 to 20 mass% of the phosphate compound (C) be
contained with respect to 100 mass% of the solid content of the resin film (A). In a
case of a content of less than 0.01 mass%, the content is small and thus there may be
cases where the effect of enhancing corrosion resistance is not obtained. In a case of
a content of higher than 20 mass%, there may be cases where the resin-based film
becomes brittle and the effect of enhancing corrosion resistance of worked parts is not
obtained.
[0109]
It is preferable that the resin film (A) according to this embodiment fiirther
contain at least one type of cross-linking agent (D) selected from the group consisting
of a silane coupling agent, a crosslinkable zirconium compound, and a crosslinkable
titanium compound. These may be used singly or in a combination of two or more
types thereof
[0110]
In the case where at least one type of cross-linking agent (D) selected from the
group consisting of a silane coupling agent, a crosslinkable zirconium compound, and
a crosslinkable titanium compound is contained, adhesion between the coated layer and
the resin film (A) is further enhanced.
- 41 -
[0111]
The silane coupling agent is not particularly limited. For example, vinyl
trimethoxysilane, vinyl triethoxysilane, y-aminopropyltrimethoxy silane, yaminopropylethoxy
silane, N- [2-(N-vinylbenzylamino)ethyl] -3 -
aminopropyltrimethoxysilane, y-methacryloxypropylmethyldimethoxysilane, ymethacryloxypropyltrimethoxysilane,
y-methacryloxypropylmethyldiethoxysilane, ymethacryloxypropyltriethoxysilane,
y-glycidoxypropyltriethoxysilane, yglycidoxypropylmethyldiethoxysilane,
y-glycidoxypropyltrimethoxysilane, 2-(3,4-
epoxycyclohexyl)ethyltrimethoxysiIane, N-p-(aminoethyl)-yaminopropyltrimethoxysilane,
N-p-(aminoethyl)-y-aminopropyltriethoxysilane, N-P"
(aminoethyl)-y-aminopropylmethyldimethoxysilane, N-phenyl-yaminopropyltrimethoxysilane,
y-mercaptpropyltrimethoxysilane, and the like, which
are sold by Shin-Etsu Chemical Co., Ltd., Nippon Unicar Company Limited, Chisso
Corporation, Toshiba Silicone Co., Ltd., and the like can be used. The silane
coupling agents may be used singly or in a combination of two or more types thereof
[0112]
The crosslinkable zirconium compound is not particularly limited as long as it
is a zirconium-containing compound having a plurality of functional groups that can
react with a carboxyl group or a hydroxyl group. Here, a compound which is soluble
in water or an organic solvent is preferable, a water-soluble zirconium compound is
more preferable. Examples of the compound include zirconyl ammonium carbonate.
[0113]
The crosslinkable titanium compound is not particularly limited as long as it is
a titanium-containing compound having a plurality of functional groups which can
react with a carboxyl group or a hydroxyl group. For example, dipropoxytitanium
- 42 -
M
bis(triethanolaminate), dipropoxy-titanium bis(diethanolaminate), propoxytitanium
tris(diethanolaminate), dibutoxytitaniumbis(triethanolaminate), dibutoxytitanium
bis(diethanolaminate), dipropoxy-titanium bis(acetylacetonato), dibutoxy-titanium
bis(acetylacetonato), a salt of dihydroxy titanium bis(lactato) monoammonium, a salt
of dihydroxy titanium bis(IaGtato) diammonium,
propanedioxytitaniumbis(ethylacetoacetate), oxotitaniumbis(monoammonium oxalate),
isopropyltri(N-amidoethylaminoethyl)titanate, and the like can be used. The crosslinking
agents may be used singly or in a combination of two or more types thereof
[0114]
In the case where at least one type of cross-linking agent (D) selected from the
group consisting of a silane coupling agent, a crosslinkable zirconium compound, and
a crosslinkable titanium compound is contained, the content thereof is preferably 0.1 to
50 mass% with respect to 100 mass% of the solid content of the aqueous resin (A). In
a case of a content of less than 0.1 mass%, the content is "small and thus there may be
cases where the effect of enhancing adhesion is not obtained, and in a case of a content
of higher than 50 mass%, there may be cases where stability of the aqueous
composition is degraded.
[0115]
It is preferable that the resin film (A) according to this embodiment further
contain at least one type of cross-linking agent (E) selected from the group consisting
of an amino resin, a polyisocyanate compound and a blocked substance thereof, an
epoxy compound, and a carbodiimide compound. The cross-linking agents may be
used singly or in a combination of two or more types thereof
[0116]
In the case where at least one type of cross-linking agent (E) selected from the
- 43 -
'p
group consisting of an amino resin, a polyisocyanate compound and a blocked substate
thereof, an epoxy compound, and a carbodiimide compound is contained, the crosslink
density is increased, and the barrier properties of the resin-based film are enhanced,
thereby further enhancing corrosion resistance.
[0117]
The amino resin is not particularly limited. For example, a melamine resin, a
benzoguanamine resin, a urea resin, a glycoluril resin, and the like can be used.
[0118]
The polyisocyanate compound is not particularly limited. For example,
hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene
diisocyanate, and the like can be used. In addition, the blocked substance thereof is a
blocked substance of the polyisocyanate compound.
[0119]
The epwxy compound is not particularly limited as long as it has a plurality of
oxirane rings. For example, diglycidyl ester adipate, diglycidyl ester phthalate,
diglycidyl ester terephthalate, sorbitan polyglycidyl ether, pentaerythritol polyglycidyl
ether, glycerin polyglycidyl ether, trimethylpropan polyglycidyl ether, neopentyl glycol
polyglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl
ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 2,2-bis-
(4'-glycidyl oxyphenyl)propane, tris(2,3-epoxypropyl)isocyanurate, bisphenol A
diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, and the like can be used.
[0120]
Examples'of the carbodiimide compound include compounds obtained by
synthesizing isocyanate-terminated polycarbodiimide through a condensation reaction
of a diisocyanate compound such as aromatic diisocyanate, aliphatic diisocyanate, and
- 44 -
^
alicyclic diisocyanate accompanied with the release of carbon dioxide, and thereafter
adding a hydrophilic segment having a functional group which has the reactivity with
an isocyanate group.
[0121]
It is preferable that 0.1 to 50 mass% of at least one type of cross-linking agent
(E) selected from the group consisting of an amino resin, a polyisocyanate compound
and a blocked substate thereof, an epoxy compound, and a carbodiimide compound is
contained with respect to 100 mass% of the solid content of the resin film (A), hi a
case of a content of less than 0.1 mass%, the content is small and thus there may be
cases where the effect of enhancing corrosion resistance is not obtained, and in a case
of a content of higher than 50 mass%, there may be cases where the resin film becomes
brittle and the effect of enhancing corrosion resistance of worked parts is not obtained.
[0122]
The resin film (A) according to this embodiment may further contain at least
one type (F) selected from the group consisting of a vanadium compound, a tungsten
compound, and a molybdenum compound. These may be used singly or in a
combination of two or more types thereof
[0123]
By containing at least one type (F) selected from the group consisting of a
vanadium compound, a tungsten compound, and a molybdenum compound, the
corrosion resistance of the resin film according to this embodiment is enhanced.
[0124]
The vanadium compound is not particularly limited. Well-known vanadiumcontaining
compounds can be used, and for example, vanadic acid, vanadate such as
ammonium vanadate and sodium vanadate, phosphovanadic acid, phosphovanadate
- 45 -
such as ammonium phosphovanadate, and the like can be used.
[0125]
The tungsten compound is not particularly limited. Well-known tungstencontaining
compounds can be used, and for example, tungstic acid, tungstate such as
ammonium tungstate and sodium tungstate, phosphotungstate such as phosphotungstic
acid, ammonium phosphotungstate, and the like can be used.
[0126]
The molybdenum compound is not particularly limited. Well-known
molybdenum-containing compounds can be used, and for example, molybdate can be
used. The skeleton and the condensation degree of the mplybdate are not limited, and
examples thereof include orthomolybdate, paramolybdate, and metamolybdate. In
addition, any salts such as a single salt and double salts are included, phosphate
molybdate or the like can be used as the double salts.
[0127]
In the case where at least one type (F) selected from the group consisting of a
vanadium compound, a tungsten compound, and a molybdenum compound is
contained, the content is preferably 0.01 to 20 mass% with respect to 100 mass% of the
solid content of the resin film (A). In a case of a content of less than 0.01 mass%, the
content is small and thus there may be cases where the effect of enhancing corrosion
resistance is not obtained. On the other hand, in a case of a content of higher than 20
mass%, there may be cases where the resin-based film becomes brittle and the effect of
enhancing corrosion resistance of worked parts is not obtained.
[0128]
The resin film (A) according to this embodiment may further contain a
polyphenolic compound (G). -
- 46 -
[0129]
Since the polyphenolic compound (G) is contained, corrosion resistance of the
resin-based film and adhesion of a post-coating film in a case of being used for postcoating
are enhanced.
[0130]
The polyphenolic compound (G) is a compound having two or more phenolic
hydroxyl groups bonded to a benzene ring or a condensate thereof Examples of the
compound having two or more phenolic hydroxyl groups bonded to the benzene ring
include gallic acid, pyrogallol, and catechol. The condensate of the compound having
two or more phenolic hydroxyl groups bonded to the benzene ring is not particularly
limited, and for example, polyphenolic compounds that are widely distributed in the
plant kingdom, typically called tannic acid, and the like can be used. Tannic acid is a
generic term for aromatic compounds with complex structures having a number of
phenolic hydroxyl groups that are widely distributed in the plant kingdom. The
tannic acid may hydrolysable tannic acid or condensed tannic acid. The tannic acid is
not particularly limited. For example, hamameli tannin, persimmon tannin, tea tannin,
gallnut tannin, gallate tannin, myrobalan taimin, divi-divi tannin, algarovilla tannin,
valonia tarmin, catechin tannin, and the like can be used.
[0131]
As the tannic acid, some kind of the tannic acid which are commercially
available, for example, "tarmic acid essence A", "B tannic acid", "N tannic acid",
"industrial tannic acid", "purified tannic acid", "Hi tannic acid", "F tannic acid", and
"station tannic acid" (all of which are manufactured by Dainippon Pharmaceutical Co.,
Ltd.), "tannic acid: AL" (manufactured by Fuji Chemical Industry Co., Ltd.), and the
like can be used. The polyphenolic compounds may be used singly or in a
47
^H
combination of two or more types thereof
[0132]
It is preferable that 0.1 to 50 mass% of the polyphenolic compound (G) is
contained with respect to 100 mass% of the solid content of the resin film (A). In a
case of a content of less than 0.1 mass%, the content is small and thus there may be
cases where the effect of enhancing corrosion resistance is not obtained, and in a case
of a content of higher than 50 mass%, there may be cases where stability of the
aqueous composition is degraded.
[0133]
The resin film according to this embodiment may further be blended with
other additives. For example, pigments may be blended. As the pigment, for
example, various coloring pigments such as inorganic pigments including titanium
oxide (TiOi), zinc oxide (ZnO), calcium carbonate (CaCOs), barium sulfate (BaS04),
alumina (AI2O3), kaoling clay, carbon black, and iron oxides (FeaOs, Fe304) and
organic pigments can be used.
[0134]
In the method of painting the resin film (A), the aqueous composition which is
the raw material of the resin film (A) is applied onto the surface of the coated steel
sheet to form a film. The application method is not particularly limited. For
example, roll coating, air spraying, airless spraying, dipping, and the like, which are
generally used, may be appropriately employed. In order to increase the hardenability
of the film, it is preferable that an article to be painted is heated in advance, or the
article to be painted is thermally dried after painting. As a thermal drying method,
any method including hot air, induction heating, near-infrared light, far-infrared light,
and the like may be used, or the methods may be used in a combination. In the case
- 48 -
M
of the thermal drying, the heating temperature of the article to be painted is 50 to
250°C, and preferably 70 to 220°C. When the heating temperature is less than 50°C,
there may be cases where the evaporating rate of moisture is low, sufficient film
forming properties are not obtained, and corrosion resistance is degraded. On the
other hand, when the heating temperature is higher than 250°C, the resin is thermally
decomposed and thus corrosion resistance is degraded, and the appearence becomes
poor due to yellowing or the like. A drying time in the case of the thermal drying
after painting is preferably 1 second to 5 minutes. In addition, when the resin is cured
by electron beams or ultraviolet light, a curing may be achieved by such irradiation or
may be used in combmation with the thermal drying.
[0135]
[Fourth Embodiment]
On the upper surface of the coated layer of the surface-treated steel sheet
obtained in the first or second embodiment, one or more layers of film obtained by
applying and drying a water-based metal surface treatment agent that contains an
organic silicon compound (W) including a silane coupling agent (I) are fiirther formed.
[0136]
In addition, there may be cases where the film is referred to as a film
according to this embodiment.
The organic silicon compound (W) which is an essential component of the
water-based metal surface treatment agent in this embodiment can be obtained by
blending a silane coupling agent (I) that contains one or more amino groups in the
molecules with a silane coupling agent (J) that contains one or more glycidyl groups in
the molecules. A blending ratio of the silane coupling agent (I) to the silane coupling
agent (J) is, in terms of sohd content mass ratio [(I)/(I)], preferably 0.5 tal.7, more
- 49 -
preferably 0.7 to 1.7, and most preferably 0.9 to 1.1. When the solid content mass
ratio [(!)/(J)] is less than 0.5, fmgerprint resistance, bath stability, and black deposit
resistance are significantly degraded, that is not preferable, hi contrast, when the
ratio exceeds 1.7, water resistance is significantly degraded, that is not preferable.
[0137]
The silane coupling agent (I) that contains one or more amino groups in the
molecules according to this embodiment is not particularly limited. Examples thereof
include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and the like.
As the silane coupling agent (J) that contains one or more glycidyl groups in the
molecules, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and
the like can be used.
[0138]
A method of manufacturing the organic silicon compound (W) in this
embodiment is not particularly limited, and a method of sequentially adding, to water
adjusted to pH4, the silane coupling agent (I) and the silane coupling agent (J) and
stirring the resultant for a predetermined time may be employed.
[0139]
In addition, in the organic silicon compound (W), there are two or more
functional groups (a) expressed by the formula -SiR^R^R^ (in the formula, R \ R^, and
R^ each independently represent an alkoxy group or a hydroxyl group, and at least one
thereof represents an alkoxy group) in the molecules, and it is preferable that the
number of functional groups (a) that contain one or more of at least one type of
hydrophilic functional group (b) selected from the group consisting of a hydroxyl
group (different from that can be included in the functional groups (a)) and an amino
group be two or more. In a case where the number of functional groups, (a) is one,.
50
«
adhesion to the surface of a metal material and film forming properties are degraded,
and thus there is a concern that black deposit resistance may be degraded. The
number of carbon of alkoxy groups in the definition of R^ R^, and R^ of the fiinctional
groups (a) is not particularly limited, but is preferably 1 to 6, more preferably 1 to 4,
and most preferably 1 or 2. The ratio of the functional groups (b) being present may
be one or more in a molecule.
The average molecular weight of the organic silicon compound (W) is
preferably 1000 to 10,000, and more preferably 1300 to 6000. The molecular weight
mentioned here is not particularly limited, and may use any of direct measurement
according to a TOF-MS method and converted measurement according to
chromatography. When the average molecular weight is less than 1000, water
resistance of the formed film is significantly reduced. On the other hand, when the
average molecular weight is greater than 10,000, it becomes difficult to stably dissolve
and disperse the organic silicon compound.
[0140]
It is preferable that the film according to this embodiment contain an inhibitor
component essentially having a fluorometal complex compound with at least one type
selected from titanium and zirconium. By containing the inhibitor component, an
effect of suppressing corrosion of the surface-treated steel sheet can be significantly
enhanced.
Regarding the blending amount of the fluorometal complex compound (N) of
the present invention, the solid content mass ratio [(N)/(W)] of the organic silicon
compound (W) and the fluorometal complex compound (N) is preferably 0.02 to 0.07,
more preferably 0.03 to 0.06, and most preferably 0.04 to 0.05. When the solid
content mass ratio [C1SI)/(W)] of the organic silicon compound (W) and the fluorometal
- 51 -
4
complex compound (N) is less than 0.02, the addition effect is not exhibited, that h is
not preferable. In contrast, when the ratio is greater than 0.07, the conductivity is
degraded, that is not preferable.
[0141]
It is preferable that the film according to this embodiment contain phosphoric
acid (Y). Regarding the blending amount of the phosphoric acid (Y), the solid
content mass ratio [(Y)/(W)] of the organic silicon compound (W) and the phosphoric
acid (Y) is preferably 0.03 to 0.12, more preferably 0.05 to 0.12, and most preferably
0.09 to 0.1. When the solid content mass ratio [(Y)/(W)] of the organic silicon
compound (W) and the phosphoric acid (Y) is less than 0.03, the addition effect is not
exhibited, that is not preferable. In contrast, when the ratio exceeds 0.12, the
solubility of the film in water becomes significant, that is not preferable.
[0142]
It is preferable that the film according to this embodiment contain a vanadium
compound (Z). Regarding the blending amount of the vanadium compound (Z), the
solid content mass ratio [(Z)/(W)] of the organic silicon compound (W) and the
vanadium compound (Z) is more preferably 0.05 to 0.17, more preferably 0.07 to 0.15,
even more preferably 0.09 to 0.14, and most preferably 0.11 to 0.13. When the solid
content mass ratio [(Z)/(W)] of the organic silicon compound (W) and the vanadium
compound (Z) is less than 0.05, the addition effect is not exhibited, that is not
preferable. In contrast, when the ratio exceeds 0.17, stability is extremely degraded,
that is not preferably.
[0143]
The yanadium compound (Z) is not particularly limited. Examples thereof
include vanadium(V) oxide V2O5, metavanadate HVO3, ammonium metavanadate,
- 52 -
%
sodium metavanadate, vanadium oxytrichloride VOCI3, vanadium (III) oxide V2O3,
vanadium (IV) oxide VO2, vanadium(IV) oxysulfate VOSO4, vanadium(IV)oxy
acetylacetonate VO(OC(=CH2)CH2COCH3))2, vanadium(III) acetylacetonate
(OC(=CH2)CH2COCH3))3, vanadium(III) chloride VCI3, and phosphovanadomolybdic
acid. In addition, those obtained by reducing a pentavalent vanadium compound to
tetravalent to divalent compounds using an organic compound having at least one
fiinctional group selected from the group consisting of a hydroxyl group, a carbonyl
group, a carboxyl group, primary to tertiary amino groups, an amide group, a
phosphate group, and a phosphonate group can be used.
[0144]
In addition, regarding the blending amount of the fluorometal complex
compound (N) and the vanadium compound (Z), the solid content mass ratio [(Z)/(N)]
of the fluorometal complex compound (N) and the vanadium compound (Z) needs to
be 1.3 to 6.0, is preferably 1.3 to 3.5, even more preferably 2.5 to 3.3, and most
preferably 2.8 to 3.0. When the solid content mass ratio [(Z)/(N)] of the fluorometal
complex compound (N) and the vanadium compound (Z) is less than 1.3, the effect of
adding the vanadium compound (Z) is not exhibited, that is not preferable. In
contrast, when the ratio exceeds 6.0, bath stability and black deposit resistance are
degraded, that is not preferable. Examples of the fluorometal complex compound (N)
include titanium hydrofluoric acid (O) and zirconium hydrofluoric acid (P).
[0145]
It is preferable that the film according to this embodiment contain at least one
type of metal component selected from Mg, Co, and W. By containing such metal
components, the metal components may be caused to function as an inhibitor for
elution, thereby suppressing corrosion of the surface-treated steel sheet. From this
- 53 -
point of view, it is more preferable that a cobalt compound (Co) be added to the film
according to this embodiment. It is preferable that the cobalt compound is at least
one type of cobalt compound selected from the group consisting of cobalt sulfate,
cobalt nitrate, and cobalt carbonate. In addition, regarding the blending ratio thereof,
the solid content mass ratio [(Co)/(W)] of the organic silicon compound (W) and the
cobalt compound (Co) is preferably 0.01 to 0.1, more preferably 0.02 to 0.07, and most
preferably 0.03 to 0.05. When the solid content mass ratio [(Co)/(W)] of the organic
silicon compound (W) and the cobalt compound (Co) is less than 0.01, the effect of
adding the cobalt compound (Co) is not exhibited, that is not preferable. In contrast,
when the ratio is greater than 0.1, the effect of enhancing corrosion resistance is not
obtained, that is not preferable.
[0146]
It is preferable that the above-described water-based metal surface treatment
agent is applied to the surface-treated steel sheet according to this embodiment, drying
is performed thereon at an end-point temperature of higher than 50°C and less than
250°C, and the thickness of the resultant after drying is 0.05 to 2.0 |j,m. Regarding
the drying temperature, the end-point temperature is preferably higher than 50°C and
less than 250°C, more preferably 70°C to 150°C, and most preferably 100°C to 140°C.
When the end-point temperature is 50°C or less, the solvent of the water-based metal
surface freatment agent is not completely volatilized, that is not preferable. In
contrast, when the temperature is 250°C or higher, a part of organic chains of the film
formed by the water-based metal surface treatment agent is decomposed, that is not
preferable.
The thickness of the film is preferably 0.05 to 2.0 ^m, more preferably 0.2 to
1.0 |j,m, and most preferably 0.3 to 0.6 |^m. When the thickness is less than 0.05 jam,
- 54 -
the surface of the metal material caimot be painted, and thus there may be cases where
the effect of enhancing corrosion resistance is not obtained. In contrast, when the
thickness is greater than 2.0 )am, conductivity and working adhesion are degraded, that
is not preferable.
[0147]
The water-based metal surface treatment agent used in the present invention
can use a leveling agent or a water-soluble solvent, a metal stabilizer, an etching
inhibitor, a pH adjusting agent, and the like for enhancing painting properties, in a
range in which the effects of the present invention are not harmed.
[0148]
The film of the present invention may further contain a polyethylene wax (Q)
as a lubricant.
[0149]
By containing the polyethylene wax (Q), lubricity of the film is enhanced, thre
is an effect on enhancement in workability during press-forming, prevention of
scratches due to molds or handling, and prevention of abrasion flaws during
transportation of formed products or coils.
[0150]
It is preferable that 0.1 to 10 mass% of the polyethylene wax (Q) is contained
with respect to 100 mass% of the solid content of the film. In a case of a content of
less than 0.1%, the effect of enhancing workability is small, and in a case of content of
higher than 10%, there may be cases where corrosion resistance is degraded.
[0151]
It is more preferable that the particle diameter of the wax is 0.1 to 5 \xm.
When the particle diameter exceeds 5 ^im, there is a possibility that the distribution of
- 55 -
the solidified wax may become uneyen or the wax may be peeled off from the resinbased
film. In a case of a particle diameter of less than 0.1 |im, there may be cases
where workability is insufBcient.
[0152]
[Modified Example of Fourth Embodiment]
The above-described film may be a composite film obtained by applying and
drying a water-based metal surface treatment agent that further includes an organic
resin (GB) in addition to the organic silicon compound (W) including the silane
coupling agent (I). In this case, those described below are preferable. In addition,
there may be cases where the composite film is referred to as a composite fikn
according to this embodiment.
[0153]
The organic silicon compound (W) is obtained by blending a silane coupling
agent (I) that contains one or more amino groups in the molecules with a silane
coupling agent (J) that contains one or more glycidyl groups in the molecules at a
predetermined solid content mass ratio [(I)/(J)]. The blending ratio of the silane
coupling agent (I) and the silane coupling agent (J) is, in terms of solid content mass
ratio [(I)/(J)], preferably a ratio of 0.50 to 0.75, more preferably 0.50 to 0.65, and most
preferably 0.55 to 0.65. When the solid content mass ratio [(I)/(J)] is less than 0.50,
hydrophobicity and self-crosslinking properties of the organic silicon compound (W)
become strong, and thus the treatment agent stability is significantly degraded. In
contrast, when the solid content mass ratio [(I)/(J)] exceeds 0.75, hydrophilicity of the
organic silicon compound (W) becomes too strong, and thus water resistance of the
obtained film is significantly degraded.
[0154] ..
- 56 -
^
The silane coupling agent (I) that contains one or more amino groups in the
molecules in this embodiment is not particularly limited. For example, 3-
aminopropyltriethoxysilane, 3-aminopropyItrimethoxysilane, and the like can be used.
As the silane coupling agent (J) that contains one or more glycidyi groups in the
molecules, for example, 3-glycidoxypropyltrimethoxysilane, 3-
glycidoxypropyltriethoxysilane, and the like can be used.
[0155]
A method of manufacturing the organic silicon compound (W) described
above is not particularly limited. For example, there is a method of sequentially
adding, to water adjusted to pH4, the silane coupling agent (I) and the silane coupling
agent (J) and stirring the resultant for a predetermined time.
[0156]
It is preferable that the number of functional groups (a) in the organic silicon
compound (W) is two or more. In a case where the number of functional groups (a) is
one, adhesion to the surface of a zinc-plated material, self-crosslinking properties of
the organic silicon compound (W), bonding to a polyether polyurethane resin (K) are
degraded, and thus there may be cases where the film is not sufficiently formed. In
this case, an effect by forming the composite film on the coated layer is not obtained.
The number of carbon atoms of the alkyl group and the alkoxy group in the definition
of R^, R^, and R^ of the functional groups (a) is not particularly limited, but is more
preferably 1 to 6, even more preferably 1 to 4, and most preferably 1 or 2.
[0157]
Moreover, in the organic silicon compound (W), the ratio of a functional
group (b) expressed by the formula -SiR^R^R^ (in the formula, R \ R^, and R^ each
independently represents an alkoxy group or a hydroxyl group, and at least one thereof
57 -
represents an alkoxy group) in the molecules may be one or more in a molecule. In
addition, the average molecular weight is preferably 1000 to 10,000, and more
preferably 1300 to 6000. The molecular weight mentioned here is not particularly
limited, and may use any of direct measurement according to a TOF-MS method and
converted measurement according to chromatography. In addition, it is preferable
that GFC (gel filtration chromatography) is used and ethylene glycol be used as
molecular weight standard substances. When the average molecular weight obtained
by the same method is less than 1000, solubility of the organic silicon compound in
water becomes strong, and thus water resistance of the formed film is significantly
reduced. On the other hand, when the average molecular weight is greater than
10,000, it becomes difficult to stably dissolve and disperse the organic silicon
compound (W).
[0158]
The type of the organic resin (GB) as an essential component is not
particularly limited, and for example, a polyether polyurethane resin (K) is preferably
used.
In the case where the polyether polyurethane resin (K) is used, it is preferable
to have at least one structural unit (L) selected from the group consisting of a structural
unit (LI) expressed by the following general formula [1], an alicyclic structure (L2)
having 4 to 6 carbon atoms, and an aromatic ring structure (L3) having 6 carbon atoms.
The structural unit (LI) acts as a point that reacts to the organic silicon compound (W).
Therefore, when the structural unit (LI) is included, the degree of cross-linking is
increased and corrosion resistance or cleaner resistance is significantly enhanced. In
addition, when the alicyclic structure (L2) having 4 to 6 carbon atoms is included, the
structure is entangled with the organic silicon compound (W) during film formation,
- 58 -
and the same effect as that of the case of being cross-linked is obtained. In addition,
when the aromatic ring structure (L3) is included, the barrier properties of the aromatic
ring are imparted to the polyether polyurethane resin (K). Therefore, although the
cross-linking reaction or the entangling reaction does not occur, the same effects as
those are obtained.
[0159]
[Chem. 1]
II I
O fit 1
[0160]
As the type of the organic resin, a polyester polyurethane resin is not
preferable because hydrolysis occurs due to acids or alkalis. Polycarbonate
polyurethane is likely to form a film that is hard and brittle and has degraded adhesion
while the working is in process and degraded corrosion resistance of worked parts, and
is thus not preferable.
[0161]
Although R9, RIO, and Rll in the structural unit (LI) are not particularly
limited, it is preferable that R9 is a monovalent organic residue selected from the group
consisting of a hydrogen atom, an alkyl group, an aryl group, and an aralkyl group, it is
preferable that RIO and Rll each independently are a functional group selected from
the group consisting of an alkoxyl group, an acyloxy group, a hydroxy! group, and a
halogen atom, it is most preferable that R9 is an alkyl group, and it is most preferable
that Rl 0 and Rl 1 are hydroxyl groups. The number m of ethylene chains of the
structural unit (LI) is not particularly limited, but is preferably 1 to 5 and most
59
^
preferably 2 or 3.
[0162]
The polyether polyurethane resin (K) according to this embodiment is not
particularly limited. Examples thereof include a urethane resin which is a
polycondensate of polyether polyol and an aliphatic, alicyclic, or aromatic
polyisocyanate, and polyurethane obtained by using polyol having an (substituted)
amino group as a part of polyol used. As the polyether polyol, those obtained by
addition-polymerizing one or more types of compounds such as ethylene oxide,
propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, tetrahydrofuran, and
cyclohexylene using ethylene glycol, diethylene glycol, triethylene glycol, propylene
glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol,
saccharose, methylene glycol, glycerine, and the like as an initiator can be used. As
the polyisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene
diisocyanate, dicyclohexylmethane diisocyanate, cyclohexylene diisocyanate,
hexamethylenediisocyanate, lysine diisocyanate, and the like can be used.
[0163]
In a case where the polyether polyurethane resin (K) contains the structural
unit (LI), this structural unit (LI) can be obtained at a stage in which a skeletal
terminal of the polyether polyurethane resin (K) becomes isocyanate by a reaction of
the terminal isocyanate of the polyether polyurethane resin (K) and primary amine
using an organic compound having both primary amine and trialkoxysilane.
Examples of the organic compound having both primary amine and trialkoxysilane
include 3-aminopropyltriethoxysilane, and 3-aminopropyltrimethoxysilane.
[0164]
The composite film according to this embodiment preferably contain a
- 60 -
1^
cationic phenolic resin (M), and in tliis case, the cationic phenolic resin (M) preferably
has a bisphenol A skeleton. The above-mentioned cationic phenolic resin (M) is not
particularly limited, but is a novolac-type phenolic resin having bisphenol A as the
main skeletal structure by condensing bisphenol A, and may include a compound
having a form three-dimensionally condensed as well as a linear compound. The
cationic properties of the cationic phenolic resin (M) are not particularly limited. For
example, it is preferable that, in an aromatic ring in the bisphenol A skeleton, -
CH2NHCH2OH and/or -CH2NHCH2OC2H5 added by removing a hydrogen atom
bonded to a carbon atom included in the aromatic ring be exhibited by being
neutralized with inorganic acid ions such as sulfuric acid ions and phosphoric acid ions
or organic acid ions such as nitric acid ions and formic acid ions and forming
quaternary ammonium salts. In addition, as the neutralizing acid, phosphoric acid is
most preferable.
[0165]
It is preferable that the composite film according to this embodiment contain
an inhibitor compoiient (d) essentially having a fluorometal complex compound (N)
with at least one type selected from titanium and zirconium. By containing the
inhibitor component, the effect of suppressing corrosion of the surface-treated steel
sheet is significantly enhanced.
Examples of the fluorometal complex compound (N) having titanium include
titanium hydrofluoric acid (O), and examples of the fluorometal complex compound
(N) having zirconium include zirconium hydrofluoric acid (P).
[0166]
In addition, in a case where the inhibitor component (d) contains both the
titanium hydrofluoric acid (O) and the zirconium hydrofluoric acid (P),_regardmg tlie
- 61 -
#
blending ratio thereof, the metal component mass ratio [(Mo)/(Mp)] of a Ti amount
(Mo) included in the titanium hydrofluoric acid(O) to a Zr amount (Mp) included in
the zirconium hydrofluoric acid (P) is preferably in a range of 0.5 to 0.8, more
preferably 0.6 to 0.8, and most preferably 0.6 to 0.7. When the metal component
mass ratio [(Mo)/(Mp)] is in a predetermined range, the ratio of titanium or a film of
oxides thereof which are produced from the titanium hydrofluoric acid and have
relatively high workability and low alkali resistance, and zirconium or oxides thereof
which are relatively hard and brittle and have high alkali resistance becomes
appropriate. As a result, an ability to follow the deformation of the film associated
with the plastic deformation of the material is increased, and thus film defects are less
likely to occur and corrosion resistance is less likely to be degraded. In contrast,
when the ratio exceeds 0.8, the ratio of titanium or a film of oxides thereof which have
relatively low alkali resistance is increased, and thus the alkali resistance of the film is
degraded, so that the effect of enhancing corrosion resistance is not obtained.
[0167]
It is preferable that the composite film according to this embodiment contain a
phosphoric acid (Y). The phosphoric acid (Y) is not particularly limited. Examples
thereof include phosphoric acid, an ammonium salt of phosphoric acid, an alkali metal
sah of phosphoric acid, an alkaline-earth metal salt of phosphoric acid. These have
an effect of mainly imparting corrosion resistance. Elution properties of the
phosphoric acid can be controlled according to the types of salts of the phosphate
compound, and a time to hold corrosion resistance can be lengthened. Among these,
phosphoric acid or magnesium biphosphate can obtain a higher effect of improving
corrosion resistance and is thus preferable. It is more preferable to use phosphoric
acid and magnesium biphosphate in combination.
- 62 -
^
[0168]
It is preferable that the composite film according to this embodiment contain
the vanadium compound (Z). The vanadium compound (Z) is not particularly limited.
For example, those obtained by reducing vanadium (V) of a compound such as
vanadium(V) pentoxide "V2O5", metavanadate "HVO3", ammonium metavanadate
"NH4VO3", sodium metavanadate "NaVOs", and vanadium oxytrichloride "VOCI3" to
vanadium (IV) using a reducing agent such as alcohols and organic acids, a vanadium
(IV)-containing compound such as vanadium (TV) dioxide "VO2", vanadium(IV) oxy
acetylacetonate "VO(C5H702)2", and vanadium(IV) oxysulfate VOSO4, those obtained
by oxidizing vanadium (III) of a compound such as vanadium acetylacetonate
"V(C5H702)3", vanadium trioxide "V2O3", and vanadium trichloride "VCI3" to
vanadium (IV) using an arbitrary oxidizing agent, and the like may be used.
[0169]
It is preferable that the water-based metal surface treatment agent described
above include a polyethylene wax (Q) described later in addition to the film-forming
component (c) and the inhibitor component (d), is made of an aqueous medium, and
haveapHof4to6.
[0170]
The polyethylene wax (Q) is not particularly limited, and the number average
particle diameter thereof is preferably 0.1 to 4.0 )am, more preferably 0.2 to 3.0 [am,
and most preferably 0.3 to 2.5 |j,m. When the number average particle diameter is
less than 0.1 |j,m, the amount of the polyethylene wax exposed to the surface of the
film is small, and the coeflFicient of friction is increased, that is not preferable. In
contrast, when the diameter exceeds 4.0 |j,m, the thickness of the polyethylene wax
with respect to that of the film is significantly increased, and thus the wax is not held in
- 63 -
the film but is peeled off by slight sliding. Therefore, the effect of reducing the
coefficient of friction is not exhibited, hi addition, the density of the polyethylene
wax (Q) is preferably 0.90 to 0.96 g/m^, more preferably 0.90 to 0.94 g/m^, and most
preferably 0.91 to 0.93 g/m^. When the density thereof is less than 0.90 g/m^, the
softening point and hardness are reduced, the film itself is softened, and thus
workability is degraded, that is not preferable. On the other hand, when the density
exceeds 0.96 g/m^, the coefficient of static friction becomes too low, and thus a roll
slip or coil collapse occurs, resuhing in degradation in operability.
[0171]
It is preferable that the pH of the water-based metal surface treatment agent
described above be 4 to 6. When the pH is less than 4, the material is excessively
etched, and a large amount of the material penetrates into chemicals, thereby degrading
stability of chemicals. On the other hand, when the pH exceeds 6, the solubility of
the above-described inhibitor component (d) is significantly reduced, and thus stability
is degraded.
[0172]
Regarding the blending ratio of the organic silicon compound (W) according
to this embodiment and the organic resin (GB) by the polyether polyurethane resin (K)
in terms of solid content, the solid content mass ratio [(GBxK)/(W)] of the organic
silicon compound (W) and the organic resin (GB) by the polyether polyurethane resin
(K) is preferably 0.33 to 0.90, is more preferably 0.33 to 0.80, and most preferably
0.35 to 0.70. When the solid content mass ratio [(GBxK)/(W)] is less than 0.33, the
barrier properties of the film-forming component (c) are degraded, that is not
preferable. In contrast, when the ratio exceeds 0.90, adhesion to the material caused
by the organic silicon compound (W) is significantly degraded, and thus overall
- 64 -
4&
performance is degraded.
[0173]
Regarding the blending ratio of the organic resin (GB) according to this
embodiment by the polyether polyurethane resin (K) and the cationic phenolic resin
(M) in terms of solid content, the solid content mass ratio [(M)/(GBxK)] of the organic
resin (GB) by the polyether polyurethane resin (K) and the cationic phenolic resin (M)
is preferably 0.010 to 0.030, more preferably 0.010 to 0.025, and most preferably 0.010
to 0.022. When the mass ratio [(M)/(GBxK)] is less than 0.010, an effect of adding
the cationic phenolic resin (M) is not exhibited, and corrosion resistance or solvent
resistance is degraded, that is not preferable. When the mass ratio exceeds 0.030, the
film is colored in light yellow by the phenolic resin, and significant yellowing occurs
under a high-humidity environment or an environment exposed to ultraviolet light, that
is not preferable.
[0174]
In this embodiment, the blending ratio of Si (Siw) derived from the organic
silicon compound (W) in the inhibitor component (d), and a Ti amount (Mo) of the
titanium hydrofluoric acid (O) and a Zr amount (Mp) of the zirconium hydrofluoric
acid (P), the metal component mass ratio [(IV[o+Mp)/(Siw)] of Si (Siw) derived fi-om the
organic silicon compound (W), and aTi amount (Mo) of the titanium hydrofluoric acid
(O) and aZr amount (Mp) of the zirconium hydrofluoric acid (P) is preferably 0.08 to
0.20, more preferably 0.08 to 0.17, and most preferably 0.08 to 0.15. When the metal
component mass ratio [(Mo+Mp)/(Siw)] is less than 0.08, the amount of titanium,
zirconium, or a compound film thereof generated &om the titanium hydrofluoric acid
and the zirconium hydrofluoric acid during film formation is small, resulting in
reduction in corrosion resistance.. On the other hand, when the ratio exceeds 0.20, the
65
surface coverage of the material of the film made fi"om titanium, zirconium, or oxides
thereof described above is increased, points that react to the material of the organic
silicon compound (W) are reduced, and thus an effect of imparting adhesion by the
organic silicon compound (W) is reduced, hi this case, the overall effect of the
formation of the composite film is degraded.
[0175]
In this embodiment, the solid content mass ratio [(Y)/(W)] of the organic
silicon compound (W) and the phosphoric acid (Y) is preferably 0.020 to 0.110, more
preferably 0.030 to 0.110, and most preferably 0.040 to 0.100. When the solid
content mass ratio [(Y)/(W)] is less than 0.020, the effect of enhancing alkali resistance,
corrosion resistance, and the like, which is the effect obtained by adding the
phosphoric acid (Y), is not exhibited. On the other hand, when the ratio exceeds
0.110, chemical stability is degraded.
[0176]
In this embodiment, the solid content mass ratio [(Z)/(W)] of the organic
silicon compound (W) and the vanadium compound (Z) is preferably 0.020 to 0.060,
more preferably 0.025 to 0.060, and most preferably 0.030 to 0.055. When the solid
content mass ratio [(Z)/(W)] is less than 0.020, an inhibitor effect caused by the
vanadium compound (Z) is not obtained. On the other hand, when the ratio exceeds
0.060, the film is likely to be colored in yellow due to increase in humidity by a
complex compound of the vanadium compound and organic substances included in the
film.
[0177]
In this embodiment, in a case where the structural unit (LI) is contained in the
polyether polyurethane resin (K), regarding the blending ratio of the organic silicon
- 66 -
compound (W) and the polyether polyurethane resin (K), the mass ratio
[(SiK)/(Siw+SiK)] of Si (SIK) derived &om the structural unit (LI) included in the
polyether polyurethane resin (K) to the sum of Si (Siw) derived from the organic
silicon compound (W) and Si (SIK) derived from the structural unit (L) included in the
polyether polyurethane resin (K) is preferably 0.015 to 0.045, more preferably 0.015 to
0.040, and most preferably 0.20 to 0.040. When the mass ratio [(SiK)/(Siw+SiK)] is m
this range, the degree of cross-linking between the polyether polyurethane resin (K)
and the organic silicon compound (W) becomes appropriate, and a film having
excellent barrier properties and hardness of the film is formed. As a result, corrosion
resistance and cleaner resistance are improved and self-crosslinking properties of the
polyether polyurethane resin itself become sufficient, thereby enhancing printing
adhesion as well as workability and slidabiltiy. In addition, since dispersion stability
of the polyether polyurethane resin (K) is improved and the reaction of the organic
silicon compound (W) to the functional groups (a) and the reaction of the organic
silicon compound (W) to the material are well-balanced, sufficient adhesion is
obtained.
[0178]
In this embodiment, the mass ratio [(Q)/(W)] of the organic silicon compound
-(W) and the polyethylene wax (Q) in terms of solid content is preferably 0.05 to 0.30,
more preferably 0.07 to 0.30, and most preferably 0.10 to 0.25. When the mass ratio
[(Q)/(W)] is less than 0.05, sufficient lubricity is not exhibited. On the other hand,
when the mass ratio is 0.30 or higher, continuity of the film is hindered by the
polyethylene wax, the film is likely to be cracked, and thus there is a concern that
corrosion resistance may be degraded.
[0179]
- 67 -
It is preferable that the composite film according to this embodiment contain a
coloring pigment containmg carbon black (PI).
The addition amount of the coloring pigment is preferably 5 to 35 mass. In
such a range, the emissivity of the obtained surface-treated steel sheet is increased, and
blackening can be achieved. When the addition amount is less than 5 mass%,
enhancement of emissivity is insuflficient, that is not preferable. In addition, when the
addition amount exceeds 35 mass%, storage stability and corrosion resistance of the
metal surface treatment agent are deteriorated, that is not preferable.
[0180]
It is preferable that the composite film according to this embodiment contain
at least one type of metal component selected from Mg, Co, and W. By containing
such metal components, the metal components may be caused to fimction as an
inhibitor for elution, thereby achieving enhancement in corrosion resistance of the
surface-treated steel sheet. From a viewpoint of corrosion resistance, it is more
preferable that a cobalt compound is added. It is preferable that the cobalt compound
be at least one type of cobalt compound selected from the group consisting of cobalt
sulfate, cobalt nitrate, and cobalt carbonate.
[0181]
When the composite film according to this embodiment is formed, the
composite film is obtained by applying the above-described water-based metal surface
treatment agent and drying the resultant at an end-point temperature of 50 to 250°C.
Regarding the drying temperature, the end-point temperature is 50°C to 250°C, more
preferably 70°C to 150°C, and most preferably 100°C to 140°C. When the end-point
temperature is 50°C or less, the solvent of the water-based metal surface treatment
agent is not completely volatilized. In contrast, when the temperature exceeds 250°C,
- 68 -
#
a part of organic chains of the film formed by the water-based metal surface treatment
agent is decomposed.
[0182]
In order to enhance corrosion resistance, increasing the thickness of the film is
effective. However, since an inorganic film does not include resin components, it is
difficult to form a thick film. Furthermore, there is a problem in that conductivity is
deteriorated by thickening the film. The composite film according to this
embodiment is a composite film that contains the organic silicon compound (W) and
the organic resin (GB) in the film formed on the coated layer, it is possible to form the
film to be thick. As a result, corrosion resistance can be significantly enhanced.
Moreover, according to the composite film, even when the film is thickened,
conductivity can be maintained without being deteriorated. Moreover, hitherto, it has
been considered that there is a concern that working adhesion may be deteriorated by
forming such a composite film on the zinc-coated layer. However, by forming, as an
object on which the composite film is to be formed, the coated layer that contains zinc
and vanadium as described above, excellent working adhesion can be ensured.
[0183]
In addition, in terms of corrosion resistance and conductivity, the thickness of
the composite film is preferably 0.3 to 4.0 |^m, more preferably 0.5 to 3.0 )am, and
most preferably 1.0 to 2.0 \im. When the thickness of the composite film is less than
0.3 |j.m, the surface of the steel sheet cannot be coated, and thus the effect of enhancing
corrosion resistance is not obtained. In contrast, when the thickness exceeds 4.0 |j.m,
conductivity and adhesion are degraded.
[0184]
It is possible for the water-based metal surface treatment agent used in this ..
- 69 -
• #
embodiment to use a leveling agent or a water-soluble solvent, a metal stabilizer, an
etching inhibitor, and the like for enhancing painting properties, in a range in which the
effects of the composite film according to this embodiment are not harmed.
Examples of the leveling agent include adducts of polyethylene oxide or polypropylene
oxide and an acetylene glycol compound as a nonionic or cationic surfactant.
Examples of the water-soluble solvent include alcohols such as ethanol, isopropyl
alcohol, tert-butyl alcohol, and propylene glycol. Ketones such as ethylene glycol
monobutyl ether and ethylene glycol monoethyl ether, esters such as ethyl acetate and
butyl acetate, and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl
ketone. Examples of the metal stabilizer include a chelate compound such as EDTA
and DTPA. Examples of the etching inhibitor include an amine compound such as
ethylenediamine, triethylenepentamine, guanidine, and pyrimidine. Particularly,
those having two or more amino groups in a molecule are effective as the metal
stabilizer and thus are more preferable.
[0185]
[Fifth Embodiment]
FIG. 7 is an enlarged cross-sectional view for explaining an example of a
surface-treated steel sheet according to a fifth embodiment. The surface-treated steel
sheet according to this embodiment has a coated layer 73 formed in the method of the
first or second embodiment and a single layer of an organic resin film 72 formed on the
upper surface of the coated layer 73, on each of the surfaces of both sides of a steel
sheet 71. In the following description, there may be cases where the organic resin
film 72 is referred to as an organic resin film according to this embodiment.
[0186]
In a case where the surface-treated steel sheet has an L* value of 10 to 35, the..
70
#
surface-treated steel sheet can be used as a material having a black appearence for
various purposes, that is preferable. In a case of an L* value of higher than 35, it is
difficult to use the steel sheet as a material having a black appearence. In addition, in
a case of an L* value of less than 10, the thickness of the organic resin film is
increased or the concentration of the pigment in the film is increased. Therefore,
painting adhesion between the coated layer 73 and the organic resin film 72 is not
suflFiciently obtained, and there is a concern that corrosion resistance may be degraded.
Therefore, it is preferable that the surface-treated steel sheet according to this
embodiment have an L* value of 10 to 35, which represents brightness.
[0187]
It is preferable that the 60-degree gloss value tiiat represents glossiness in the
surface-treated steel sheet of this embodiment is 50 or less. When the gloss value of
the surface-treated steel sheet is 50 or less, the steel sheet can be used as a material
having a black appearence for various purposes. In a case of a gloss value of higher
than 50, scratches are easily noticeable during handling or press work, and thus there
may be cases where the surface-treated steel sheet carmot be used as a design material.
[0188]
The organic resin film 72 according to this embodiment will be described.
The organic resin film 72 of this embodiment is made from an organic resin that
includes a polyester resin (Al) containing a sulfonic acid group, a curing agent (Bl),
and a colorant (CI) as a coloring pigment containing carbon black, and is formed by
applying a black water-based paint that includes the polyester resin (Al) containing a
sulfonic acid group, the curing agent (Bl), and the colorant (CI) and curing the
resultant through baking and drying.
[0189] - 1
- 71 -
• *
In order to obtain excellent painting adhesion, it is more preferable that the
thickness of the organic resin film 72 is smaller in a range in which a predetermined
appearence having a sufficiently low glossiness and L* value is obtained.
Specifically, the thickness is preferably 1 to 10 |j,m, and more preferably 2 to 5 i^m.
When the thickness of the organic resin film 72 is less than 1 ^im, there may be cases
where a predetermined appearence having a sufficiently low glossiness and L* value is
not obtained or a thin-painted appearence is obtained while fine unevenness on the
coating surface is not shielded. In addition, when the thiclcness of the organic resin
film 72 exceeds 10 fim, there is a concern of inconvenience such as degradation in
painting adhesion or popping is more likely to occur during film formation.
[0190]
The thickness of the above-described organic resin film 72 can be measured
by cross-section observation or by using an electromagnetic film thickness meter. In
addition, the mass of painted film attached per unit area may be calculated by dividing
the mass by the specific gravity of the painted film or the specific gravity after drying a
paint. The mass of the painted film attached may be obtained by appropriately
selecting a technique fi^om conventional techniques such as measurement of a mass
difference before and after formation of the painted film or a mass difference before
and after the painted film is peeled off, and measurement of the amount of an element
being present, of which the content in the painted film is known in advance through
fluorescent X-ray analysis of the painted film. In addition, the specific gravity of the
painted film or the specific gravity of the paint after drying may be obtained by
appropriately selecting a technique from conventional techniques such as collection of
an appropriate amount of paint to measure the volume and mass of an isolated painted
film in a container and measurement of the volume and mass after drying the resultant
- 72 -
#
in the vessel, or calculation from the amount of painted film constituent components
being blended and the conventional specific gravity of each of the components.
[0191]
[Polyester Resin (Al) Containing Sulfonic Acid Group]
Although a polyester resin itself is hydrophobic, in a case where a sulfonic
acid group is contained in the polyester resin, high hydrophilicity is exhibited.
Therefore, the polyester resin (Al) containing the sulfonic acid group is stably
dissolved or dispersed in a water-based paint. In addition, the polyester resin (Al)
containing the sulfonic acid group enhances the compatibility between carbon black
having hydrophobic surfaces and water and has an important role of causing the carbon
black to be uniformly and stably dispersed in the water-based paint. This is achieved
by an effect in which the main skeleton of the polyester resin having hydrophobicity is
oriented in the direction of the carbon black.
[0192]
Therefore, the surface-treated steel sheet according to this embodiment has
carbon black uniformly dispersed in the organic resin film 72, and thus has extremely
excellent design properties (coloring properties and concealing properties) even when
the organic resin film 72 is thin.
The water-based paint for forming the organic resin film 72 of this
embodiment may not perform a surface hydrophilization treatment or contain a
surfactant in order to enhance the dispersability of the carbon black. Therefore, there
is no concern of corrosion resistance of the organic resin film 72 being degraded by the
surface hydrophilization treatment and the surfactant.
[0193]
The sulfonic acid group includeiin the polyester resin (Al) has an effect of
- 73 -
enhancing adhesion with the coated layer 73 disposed in contact with the organic resin
film 72. Therefore, in the surface-treated steel sheet of this embodiment, adhesion
between the organic resin fikn 72 and the coated layer 73 is excellent.
[0194]
The polyester resin (Al) containing the sulfonic acid group is not particularly
limited as long as the sulfonic acid group is contained. For example, those obtained
by dissolution or dispersion in water of the resultant obtained through
polycondensation of a polyester raw material made from a polycarboxylic acid
component and a polyol component can be used. The polycarboxylic acid component
is not particularly limited. Examples thereof include terephthalic acid, isophthalic
acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, succinic acid, glutaric acid,
adipic acid, sebacic acid, dodecanedicarboxylic acid, azelaic acid, 1,2-
cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-
cyclohexanedicarboxylic acid, dimer acid, trimellitic anhydride, and pyromellitic
dianhydride. Only one type or two or more types thereof can be arbitrarily used.
[0195]
The polyol component is not particularly limited. Examples thereof include
ethylene glycol, diethylene glycol, 1,3-propanediol, 1,2-propanediol, triethylene glycol,
2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-
propanediol, 1,4-butanediol, 2-methyl-1,4-butanediol, 2-methyl-3-methyl-1,4-
butanediol, 1,5-pentanediol, 3-methyl-l,5-pentanediol, 1,6-hexanediol, 1,4-
cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol,
hydrogenated bisphenol A, dimer diol, trimethylol ethane, trimethylol propane,
glycerine, and pentaerythritol. Only one type or two or more types thereof can be
arbitrarily used.
- 74 -
[0196]
The sulfonic acid group included in the polyester resin (Al) represents a
functional group expressed by -SO3H and may be those neutralized by alkali metals,
amines including ammonia, and the like. The neutralized sulfonic acid group may be
those assembled in a polyester resin with an already neutralized sulfonic acid group, or
those neutralized after assembling a sulfonic acid group in a resin. Particularly, a
group of sulfonic acid metal salt neutralized by alkali metals such as Li, Na, and K has
higher hydrophilicity and thus enhances dispersability of the carbon black, thereby
being appropriate for obtaining high design properties. In addition, in order to further
enhance adhesion between the organic resin film 72 and the coated layer 73, the
sulfonic acid group is preferably a group of sulfonic acid metal salt neutralized by
alkali metals, and a group of sulfonic acid sodium salt is most preferable.
[0197]
It is preferable that the polyester resin (Al) containing the sulfonic acid group
contain a urethane bond in the skeleton. By containing the urethane bond, corrosion
resistance and adhesion between the organic resin film 72 and the coating 73 is
enhanced.
A method of introducing the urethane bond in the skeleton of the polyester
resin (Al) containing the sulfonic acid group is not particularly limited. For example,
this is obtained by causing the hydroxyl group included in the polyester resin to react
with a diisocyanate compound such as hexamethylene diisocyanate, isophorone
diisocyanate, and tolylene diisocyanate.
[0198]
It is preferable that the organic resin film 72 further contain an acrylic resin
(A3) in addition to the polyester resin (Al) containing the sulfonic acidgroup. By
- 75 -
further containing the acrylic resin (A3), dispersability of the carbon black in a waterbased
black paint that becomes the organic resin film 72 can further be enhanced. As
a result, design properties (coloring properties and concealing properties) of the
organic resin film 72 can further be enhanced.
[0199]
The type of the acrylic resin (A3) is not particularly limited. For example,
those obtained by radical polymerization of unsaturated monomers such as styrene,
alkyl(meth)acrylates, (meth)acrylic acids, hydroxyalkyl(meth)acrylates, and
alkoxysilane(meth)acrylates in an aqueous solution using a polymerization initiator can
be used. In addition, the polymerization initiator is not particularly limited, and for
example, persulfates such as potassium persulfate and ammonium persulfate and an
azo compound such as azobis-cyanovaleric acid and azobisisobutyronitrile can be used.
[0200]
In a case where the acrylic resin (A3) is contained, the content thereof is
preferably 0.5 to 10 mass% with respect to 100 mass% of the polyester resin (Al)
containing the sulfonic acid group. When the content is less than 0.5 mass%, there
may be cases where an effect caused by containing the acrylic resin (A3) is not
sufficiently obtained. When the content exceeds 10 mass%, there may be cases where
corrosion resistance or workability is degraded compared to a case where the acrylic
resin (A3) is not contained.
[0201]
It is preferable that the organic resin film 72 fiirther contain a polyurethane
resin (A2) containing a carboxyl group. By further containing the polyurethane resin
(A2) containing a carboxyl group, corrosion resistance or adhesion between the
organic resin film 72 and the coated layer 73 can be enhanced.
- 76 -
[0202]
The type of the polyurethane resin (A2) containing the carboxyl group is not
particularly limited as long as the carboxyl group is contained. For example, those
obtained by causing polyols such as ethylene glycol, propylene glycol, diethylene
glycol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxypropyl
ether, glycerine, trimethylol ethane, and trimethylol propane to react with a
diisocyanate compound such as hexamethylene diisocyanate, isophorone diisocyanate.
and tolylene diisocyanate, and further chain-extending the resultant with diamine or the
like, followed by dispersion in water can be used. The chain-extension with diamine
not only increases the molecular weight of a resin, but also generates a urea group
through the reaction of an isocyanate group and an amino group. As the urea group
having high cohesive energy is contained in the resin, cohesive force of the painted
film can be further increased, and corrosion resistance or scratch resistance of the
organic resin film 72 can be further increased.
[0203]
The content of the polyurethane resin (A2) is preferably 5 to 100 mass% with
respect to 100 mass% of the polyester resin (Al) containing the sulfonic acid group.
When the content is less than 5 mass%, there may be cases where an effect caused by
containing the polyurethane resin (A2) is not sufficiently obtained. When the content
exceeds 100 mass%, there may be cases where workability is degraded compared to a
case where the polyurethane resin (A2) is not contained.
[0204]
[Curing Agent (Bl)]
The organic resin film 72 of this embodiment is obtained by curing the
polyester resinhaving high ductility and high workability with the curing agent (Bl),
- 77 -
Therefore, degradation in film forming properties caused by including the colorant
(CI) containing the carbon black is suppressed, resulting in being dense. As a result,
the organic resin film 72 of this embodiment has excellent humidity resistance,
corrosion resistance, scratch resistance, and chemical resistance.
[0205]
The curing agent (Bl) is not particularly limited as long as the polyester resin
(Al) containing the sulfonic acid group is cured. Examples thereof include a
melamine resin or a polyisocyanate compound. From the viewpoint of scratch
resistance and chemical resistance of the organic resin film 72, the melamine resin is
preferably contained.
As the melamine resin, a resin obtained by etherifying a part or all of the
methylol groups of the product obtained by condensing melamine and formaldehyde
with a lower alcohol such as methanol, ethanol, or butanol can be used.
[0206]
In the case where the curing agent (Bl) contains the melamine resin, the
content of the melamine resin is preferably 30 to 100 mass% in the curing agent (Bl).
When the content is less than 30 mass%, there may be cases where the effect obtained
by containing the melamine resin is not sufficiently obtained.
[0207]
The polyisocyanate compound is not particularly limited. Examples thereof
include hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate,
and tolylene diisocyanate. In addition, examples of the blocked substance thereof
include a blocked substance of hexamethylene diisocyanate, a blocked substance of
isophorone diisocyanate, a blocked substance of xylylene diisocyanate, and a blocked
substance of tolylene diisocyanate, which is a blocked substance of a polyisocyanate .
- 78 -
compound. These curing agents may be used singly or in a combination of two or
more types thereof.
[0208]
The content of the curing agent (Bl) is preferably 5 to 35 mass% with respect
to 100 mass% of the whole organic resins (in a case where the organic resin film 72
includes a resin other than the polyester resin (Al), the whole resins includes the resin).
When the content is less than 5 mass%, baking and curing are insufficiently achieved.
and thus there may be cases where the effect of enhancing corrosion resistance is not
obtained or cases where humidity resistance, scratch resistance, and chemical
resistance are degraded. On the other hand, when the content exceeds 35 mass%,
baking and curing are excessively achieved, and thus there may be cases where
corrosion resistance and workability are degraded.
[0209]
[Colorant (CI)]
The colorant (CI) includes a coloring pigment containing the carbon black.
The carbon black has high concealing properties at low cost. In addition to the
carbon black, a coloring inorganic pigment such as titanium dioxide, carbon black,
graphite, and iron oxide, a coloring organic pigment such as phthalocyanine blue,
phthalocyanine green, quinacridone, azo orange, azo yellow, and azo red, and a
luminous material such as aluminum powder, titanium dioxide-coated mica powder,
and titanium dioxide-coated glass powder may fiirther included.
The carbon black is not particularly limited, and for example, well-known
carbon blacks such as furnace black, Ketjenblack, acetylene black, and charmel black
can be used. In addition, well-known ozon-treated, plasma-treated, and liquid phase
oxidation-treated carbon blacks may also be used.
- 79 -
•
[0210]
In consideration of design properties (coloring properties and concealing
properties) of the organic resin film 72 or corrosion resistance, the number average
particle diameter of the carbon black in a state of being dispersed in the painted film is
preferably 20 to 300 nm.
[0211]
Assuming that the content of the carbon black in the organic resin film 72 is X
mass% and the thickness of the organic resin film 72 is Y ^m, the absolute amount of
the carbon black may be represented by the product of the content (X mass%) of the
carbon black included in the organic resin film 72 and the thickness (Y|j,m) of the
painted film. In order to ensure design properties (coloring properties and concealing
properties) of the organic resin film 72, the product of the X and the Y, which is the
absolute amount of the carbon black included in the organic resin film 72 is preferably
18 or higher. When the product of the X and the Y is less than 18, there is a concern
that design properties (coloring properties and concealing properties) may not be
sufficiently enhanced. In addition, when the X exceeds 15, fihn forming properties of
the organic resin film 72 are degraded, and thus there is a concern that the effect of
enhancing the corrosion resistance of the surface-treated steel sheet may not be
obtained. Therefore, it is preferable that XxY>18andX<15.
[0212]
It is preferable that the organic resin film 72 further contain silica (Dl) in
order to enhance corrosion resistance and scratch resistance. The silica (Dl) is not
particularly limited, and is preferably fine silica particles such as colloidal silica or
fumed silica having primary particle diameters of 5 to 50 nm. From the viewpoint of
corrosion resistance or workability, it is preferable that the fine silica particles be
- 80 -
dispersed in the organic resin film 72 while having primary particle diameters (number
average particle diameter) of 5 to 50 run.
[0213]
The content of the silica (Dl) in the organic resin film 72 is preferably 5 to 30
mass%. When the content is less than 5 mass%, there may be cases where an effect
caused by containing the silica (Dl) is not sufficiently obtained. When the content
exceeds 30 mass%, there may be cases where corrosion resistance, workability, and the
like are degraded.
[0214]
It is preferable that the organic resin film 72 fiirther contain a lubricant (El).
By containing the lubricant (El), scratch resistance is enhanced. The lubricant (El) is
not particularly limited, and well-known lubricants can be used. It is more preferable
to use at least one type selected from a fluororesin-based lubricant and a polyolefin
resin-based lubricant.
[0215]
As the fluororesin-based lubricant, for example, polytetrafluoroethylene
(PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP),
tetrafluoroethyjene-perfluoroalkyl vinyl ether copolymer (PFA),
polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl
fluoride (PVF), ethylene-tetrafluoroethylene copolymer (ETFE), ethylenechlorotrifluoroethylene
copolymer (ECTFE), and the like can be used. A single type
of them may be used singly, or two or more types of them may be used in
combinations.
[0216]
The polyolefin resin-based resin is not particularly limited. For example, a
- 81 -
hydrocarbon-based wax such as paraffin, microcrystalline, and polyethylene,
derivatives thereof, and the like can be used. A polyethylene resin is more preferable.
The derivatives are not particularly limited, and for example, carboxylated polyolefm,
chlorinated polyolefm, and the like can be used. A single type of them may be used
singly, or two or more types of them may be used in combination.
In a case where the polyethylene resin is used, from the viewpoint of
corrosion resistance and scratch resistance, it is preferable that particles having a
number average particle diameter of 0.5 to 2 |.im are dispersed in the organic resin film
72.
[0217]
The content of the lubricant (El) in the organic resin film 72 is preferably 0.5
to 10 mass%. When the content is less than 0.5 mass%, there may be cases where an
eflfect caused by containing the lubricant (E) is not sufficiently obtained. When the
content exceeds 10 mass%, there may be cases where the effect of enhancing corrosion
resistance is not obtained or cases where workability is degraded.
[0218]
The surface-treated steel sheet according to this embodiment has excellent
corrosion resistance and painting adhesion, sufficiently suppressed glossiness, a
sufficiently low L* value, excellent adhesion and scratch resistance while the working
is in process, and an aesthetically pleasant appearence.
[0219]
Since the surface-treated steel sheet according to this embodiment has an
appearence with sufficiently suppressed glossiness, there is no need to form a film
containing a delustering agent on the surface of the organic resin film 72 or cause the
organic resin film 72 to contain a delustering agent, and low glossiness can be realized
- 82 -
with a thin film. In addition, since the adhesion between organic resin film 72 and the
coated layer 73 is excellent, an underlayer does not need to be provided between the
organic resin film 72 and the coated layer 73, thereby being manufactured.
[0220]
In this embodiment, the surface-treated steel sheet having a single layer of the
organic resin film 72 is exemplified. However, the organic resin film 72 may have
one or more layers or two or more layers. In a case where two or more layers of the
organic resin film are provided, the total thickness of the layers of the organic resin
film is preferably 1 to 10 |im.
[0221]
The organic resin film according to this embodiment is obtained by applying a
black water-based paint that includes the polyester resin (Al) containing the sulfonic
acid group, the curing agent (Bl), and the carbon black as the colorant (CI) onto the
steel sheet 71 formed with the coated layer 17, followed by baking and drying.
[0222]
The method of manufacturing the water-based paint is not particularly limited,
and examples thereof include a method of adding the polyester resin (Al) containing
the sulfonic acid group, the curing agent (Bl), and the carbon black as the colorant
(CI), which are the components of the organic resin film 72, into water, and stirring the
resultant with a disperser so as to be dissolved or dispersed.
The method of applying the water-based paint is not particularly limited, and
for example, well-known roll coating, curtain coating, die coating, spraying, bar
coating, dipping, electrostatic coating, and the like can be appropriately used.
The baking and drying method is not particularly limited, and drying may be
-performed by heating the steel sheet 71 formed with the coated layer,73 in advance or
- 83 -
heating the steel sheet 71 formed with the coated layer 73 after applying the waterbased
paint, or combining these methods.
[0223]
Regarding the baking and drying temperature, the end-point temperature is
preferably 150°C to 250°C, more preferably 160°C to 230°C, and most preferably
180°C to 220°C. When the end-point temperature is less than 150°C, baking and
curing are insufficiently achieved, and thus there is a concern that the effect of
enhancing corrosion resistance may not be sufficiently obtained. On the other hand,
when the end-point temperature exceeds 250°C, baking and curing are excessively
achieved, and thus there may be cases where the effect of enhancing corrosion
resistance is not obtained or cases where workability is degraded. The baking and
drying time is preferably 1 to 60 seconds and more preferably 3 to 20 seconds. When
the baking and drying time is shorter than 1 second, there may be cases where baking
and curing are insufficiently achieved. When the baking and drying time exceeds 60
seconds, productivity is degraded.
[0224]
[Sixth Embodiment]
Hereinafter, a case where a coloring painted film layer that includes a coloring
pigment layer is fiirther formed on the surface of the coated layer of the surface-treated
steel sheet obtained in the first or the second embodiment will be described with
reference to the drawings.
FIG. 8 A is an enlarged cross-sectional view for explaining an example of the
surface-treated steel sheet accordmg to the sixth embodiment. A surface-treated steel
sheet 81a illustrated in FIG. 8 A is manufactured by the method of the first or second
- embodiment, coloring painted film layers made from the coloring pigment layers 16
- 84 -
formed on the coated layers 82 to be in contact therewithare formed on both surfaces
of the surface-treated steel sheet 81 having the coated layers.
In the surface-treated steel sheet illustrated in FIG 8A, the case where the
coated layers 82 and the coloring painted film layers (the coloring pigment layers 16)
are formed on both surfaces of the steel sheet 81 is exemplified. However, the coated
layer 82 and the coloring painted film layer may also be formed on only one surface of
the steel sheet. In addition, it is preferable that the same layers are formed on one
surface and the other surface of the steel sheet 81 in terms of easy manufacture.
However, different layers may also be formed.
[0225]
The coloring pigment layer 16 includes a pigment and a resin and does not
include a rust-preventive agent. In this embodiment, even though the coloring
pigment layer 16 does not include the rust-preventive agent at all, the adhesion
between the coated layer 82 and the coloring painted film layer is excellent, thereby
ensuring sufficiently high corrosion resistance in the surface-treated steel sheet 81a.
When the rust-preventive agent such as a rust-preventive pigment is contained
in the coloring pigment layer 16, the coloring pigment layer 16 becomes brittle, and
workability of the surface-treated steel sheet 81a is degraded. In this embodiment,
since the coloring pigment layer 16 does not include the rust-preventive agent,
excellent workability can be ensured compared to a case where a rust-preventive agent
such as a rust-preventive pigment is included therein.
[0226]
As the pigment used in the coloring pigment layer 16, one type or two or more
types of generally well-known pigments can be used, and the pigment is not
particularly limited. - For example, titanium oxide which is a white pigment, carbon
- 85 -
black which is a black pigment, and the like can be used.
[0227]
As the resin used in the colormg pigment layer 16, one type or two or more
types of generally well-known resins, for example, a polyester resin, a urethane resin,
an acrylic resin, an epoxy resin, a fluorine-based resin, a silicon-based resin, and the
like can be used. As a curing agent for forming the coloring pigment layer 16,
generally well-known curing agents for painting such as melamine and isocyanate can
be used, hi addition, when a resin obtained by cross-linking the polyester resin with
melamine or a resin obtained by cross-linking the polyester resin with isocyanate is
used as the resin used in the coloring pigment layer 16, more excellent workability is
obtained, which is more appropriate.
[0228]
Hitherto, in a case where the polyester resin is applied to the painted film that
is directly painted onto the coated layer 82, in order to ensure adhesion with the coated
layer 82, generally, a resin with high adhesion such as an epoxy resin among polyester
resins is added for use.
On the other hand, the surface-treated steel sheet according to this
embodiment can ensure sufficient painting adhesion even when only the resin obtained
by cross-linking the polyester resin with the melamine curing agent or the resin
obtained by cross-linking the polyester resin with the isocyanate curing agent is used
as the resin used in the coloring pigment layer 16, and thus the coloring pigment layer
16 is not peeled off even when strict work such as binding or bending is performed.
[0229]
In this embodiment, as described above, the coated layer 82 has excellent
painting adhesion to the painted film formed thereon. Therefore, the effect of
- 86 -
enhancing corrosion resistance, which is caused by forming the coloring pigment layer
16 on the coated layer 82, is effectively exhibited. Therefore, compared to the related
art, the thickness of the coloring pigment layer 16 can be reduced. In addition, since
the surface-treated steel sheet 81a of this embodiment has excellent adhesion between
the coated layer 82 and the coloring pigment layer 16, high corrosion resistance and
workability can be ensured even when a chemical conversion treatment layer or
primer-painted film layer is not formed between the coated layer 82 and the coloring
pigment layer 16. Therefore, like the surface-treated steel sheet 81a illustrated in FIG.
8A, the coloring pigment layer 16 (the coloring painted film layer) is formed on the
coated layer 82 to be in contact therewith. In this case, compared to the case where a
chemical conversion treatment layer and a primer-painted fikn layer are formed,
simplification of the manufacturing process can be achieved, and the lowered
manufacturing cost can be achieved.
[0230]
A process of forming the coloring painted film layer made from the coloring
pigment layer 16 which comes into contact with the coated layer 82 will be described.
The coloring pigment layer 16 can be formed by applying a paint including a pigment
and a resin onto the coated layer 82 of the surface-treated steel sheet obtained in the
method of the first or second embodiment.
[0231]
[Modified Example of Sixth Embodiment]
The surface-treated steel sheet according to this embodiment is not limited to
the above-described example illustrated in FIG. 8A. FIG. 8B is an enlarged crosssectional
view for explaining another example of the surface-treated steel sheet
according to the sixth embodiment. In a surface-treated steel sheet 81b illustrated in
87
FIG. 8B, unlike the surface-treated steel sheet 81a illustrated in FIG. 8A, the coloring
painted film layer 15 includes a primer-painted film layer 14 formed between the
coated layer 82 and the coloring pigment layer 16. In the surface-treated steel sheet
81b illustrated in FIG. 8B, the primer-painted film layer 14 is formed between the
coated layer 82 and the coloring pigment layer. 16, and thus more excellent corrosion
resistance is obtained.
[0232]
The primer-painted film layer 14 illustrated in FIG. 8B includes a resin and a
rust-preventive agent.
As the resin used in the primer-painted film layer 14, the same resin that can
be used in the coloring painted film layer 16 may be employed. The resin used in the
primer-painted film layer 14 and the resin used in the coloring painted film layer 16
may be the same or may be different fi-om each other.
[0233]
It is more preferable that the rust-preventive agent included in the primerpainted
film layer 14 use a non-chromium agent that does not include hexavalent
chromium from the viewpoint of compatibility with the environment. As the nonchromium
rust-preventive agent, those including any one of or both Si and P are
preferable. In this case, more excellent corrosion resistance is obtained. The rustpreventive
agent may include a rust-preventive pigment, may not include a rustpreventive
pigment, or may be only a rust-preventive pigment.
[0234]
Examples of the rust-preventive agent including any one of or both Si and F
include a silica-based rust-preventive pigment, a zinc phosphate-based rust-preventive
pigment, an aluminum phosphate-based rust-preventive pigment, and a magnesium
- 88 -
#
phosphate-based rust-preventive pigment. As commercially available rust-preventive
agents, for example, "SHIELDEX" (registered trademark) series as calcium-adsorbed
silica made by W. R. Grace & Co.-Coim., "K-WHITE" (registered trademark) series as
aluminum dihydrogen tripolyphosphate made by Tayca Corporation.
[0235]
In a case where the rust-preventive agent included in the primer-painted film
layer 14 is the rust-preventive pigment, the content of the rust-preventive agent in the
primer-painted film layer 14 is preferably 5 to 30 mass% in terms of solid content
concentration. In a case where the content of the rust-preventive pigment in the
primer-painted film layer 14, is in the above range, more excellent corrosion resistance
is obtained while ensuring workability. In the case where the rust-preventive agent is
the rust-preventive pigment, when the content of the rust-preventive agent in the
primer-painted film layer 14 is less than 5 mass%, there is a concern that an effect
caused by containing the rust-preventive agent may not be sufficiently exhibited. On
the other hand, when the content of the rust-preventive agent exceeds 30 mass%, the
primer-painted film layer 14 becomes brittle, and the painted film of worked parts is
likely to be peeled off in a case where molding work is performed, and thus there is a
concern that workability of the surface-treated steel sheet may be disrupted.
[0236]
In order to manufacture the surface-treated steel sheet 81b illustrated in FIG.
8B, first, the primer-painted film layer 14 is formed on the coated layer 82 to be iri
contact therewith of the surface-treated steel sheet 81 having the coated layer. The
primer-painted film layer 14 is formed by forming a painted film by applying a paint
including the resin and the rust-preventive agent onto the coated layer 82, drying and
baking the resultant, followed by water cooling.
- 89 -
#
[0237]
Next, on each of both surfaces of the steel sheet 81 where the coated layer 82
and the primer-painted film layer 14 are formed, the coloring pigment layer 16 is
formed in the same manner as the surface-treated steel sheet 81a illustrated in FIG. 8A.
Accordingly, the coloring painted film layer 15 made fi-om the coloring pigment layer
16 and the primer-painted film layer 14 is formed.
[0238]
In the surface-treated steel sheet 81b of this embodiment, since the coated
layer 82 has excellent painting adhesion to the painted film formed thereon, high
corrosion resistance and workability can be ensured even when a chemical conversion
treatment layer is not formed between the coated layer 82 and the primer-painted film
layer 14 of the coloring painted film layer 15. Therefore, like the surface-treated steel
sheet 81b illustrated in FIG. 8B, the primer-painted film layer 14 can be formed on the
coated layer 82 to be in contact therewith. In the surface-treated steel sheet 81b
illustrated in FIG. 8B, compared to the case where the chemical conversion treatment
layer is formed, simplification of the manufacturing process can be achieved, and
manufacture can be achieved at low cost.
[0239]
[Another Modified Example of Sixth Embodiment]
In order to further enhance corrosion resistance, a chemical conversion
treatment layer may be formed between the coloring painted film layer and the coated
layer in the surface-treated steel sheet according to this embodiment as necessary.
FIG. 8C is an enlarged cross-sectional view for explaining another modified
example of the surface-treated steel sheet according to the sixth embodiment. In a
surface-treated steel sheet 81c illustrated in FIG. 8C, unlike the surface-treated steel
90
#
sheet 81b illustrated in FIG. 8B, a chemical conversion treatment layer 17 is formed
between the coloring painted film layer 15 and the coated layer 82. Since the surfacetreated
steel sheet 8Ic illustrated in FIG. 8C includes the chemical conversion
treatment layer 17 formed between the coloring painted film layer 15 and the coated
layer 82, more excellent corrosion resistance is obtained.
[0240]
It is preferable that the chemical conversion treatment layer 17 illustrated in
FIG. 8C is obtained by performing a chemical conversion treatment using a treatment
liquid including silica, a silane coupling agent, and a resin. In this case, the chemical
conversion treatment layer 17 having more excellent adhesion between the coloring
painted film layer 15 and the coated layer 82 is obtained.
As the resin included in the treatment liquid of the chemical conversion
treatment, generally well-known resins such as a polyester resin, an acrylic resin, a
urethane resin, and an epoxy resin can be used. Among such resins, a water-soluble
type resin or a resin dispersed in water is more appropriate because handling of the
treatment liquid used in the chemical conversion treatment is facilitated.
[0241]
As the silica included in the treatment liquid of the chemical conversion
treatment, generally well-known silica can be used. Particularly, silica having fine
particle diameters can maintain stability in a case of being dispersed in the treatment
liquid of the chemical conversion treatment and is thus more appropriate. As the
silica contained in the treatment liquid, commercially available silica may be used.
As the commercially available silica, for example, silica gel such as "SNOWTEX N",
"SNOWTEX C", "SNOWTEX UP", and "SNOWTEX PS" (all of which are made by
NISSAN CHEMICAL INDUSTRIES, Ltd.) and "Aderaito Ar-20 Q" (made by
- 91 -
ADEKA Corporation) or powder silica such as AEROSIL #300 (made by Nippon
Aerosil Co., Ltd.), and the like can be used.
[0242]
As the silane coupling agent included in the treatment liquid of the chemical
conversion treatment, for example, y-(2-aminoethyl)aminopropyltrimethoxysilane, y-
(2-aminoethyl)aminopropylmethyldimethoxysilane, y-(2-
aminoethyl)aminopropyltriethoxysilane, y-(2-
aminoethyl)aminopropylmethyldiethoxysilane, y-(2-
aminoethyl)aminopropylmethyldimethoxysilane, ymethacryloxypropyltrimethoxysilane,
y-methacryloxypropylmethyldimethoxysilane, ymethacryloxypropyltriethoxysilane,
y-methacryloxypropylmethyldiethoxysilane, N-P-
(N-vinylbenzylaminoethyl)-y-aminopropyltrimethoxysilane, N-P -(Nvinylbenzylaminoethyl)-
y-aminopropylmethyldimethoxysilane, N-p-(Nvinylbenzylaminoethyl)-
y-aminopropyItriethoxysilane, N-p-(Nvinylbenzylaminoethyl)-
y-aminopropylmethyldiethoxysilane, yglycidoxypropyltrimethoxysilane,
y-glycidoxypropylmethyldimethoxysilane, yglycidoxypropyltriethoxysilane,
y-glycidoxypropylmethyldiethoxysilane, ymercaptopropyltrimethoxysilane,
y-mercaptopropylmethyldimethoxysilane, ymercaptopropyltriethoxysilane,
y-mercaptopropylmethyldiethoxysilane,
methyltrimethoxysilane, dimethyldimethoxysilane, methyhriethoxysilane,
dimethyldiethoxysilane, vinyltriacetoxysilane, y-chloropropyltrimethoxysilane, ychloropropylmethyldimethoxysilane,
y-chloropropyltriethoxysilane, ychloropropylmethyldiethoxysilane,
hexamethyldisilazane, yanilinopropyltrimethoxysilane,
y-anilinopropylmethyldimethoxysilane, yanilinopropyltriethoxysilane,
y-anilinopropylmethyldiethoxysilane, vinyl
- 92 -
^
trimethoxysilane, vinylmethyldimethoxysilane, vinyl triethoxysilane,
vinylmethyldiethoxysilane, octadecyldimethyl[3-(trimethoxysilyI)propyl]ammonium
chloride, octadecyldimethyl[3 -(methyldimethoxysilyl)propyl] ammonium chloride,
octadecyldimethyl [3 -(triethoxysilyl)propyl] ammonium chloride, octadecyldimethyl [3 -
(methyldiethoxysilyl)propyl] ammonium chloride, ychloropropylmethyldimethoxysilane,
y-mercaptopropylmethyldimethoxysilane,
methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and the like can
be used. When y-glycidoxypropyltrimethoxysilane having a glycidyl ether group and
y-glycidoxypropyltriethoxysilane are used, the working adhesion of the painted film is
particularly improved. Moreover, when a silane coupling agent in a triethoxy-type is
used, the preservation stability of an underlayer treatment liquid can be improved. It
is considered that this is because triethoxysilane is relatively stable in an aqueous
solution and has a low polymerization speed.
[0243]
The chemical conversion treatment layer may include a rust-preventive agent
including any one or two or more selected from tannin, tannic acid, a zirconium
compound, and a titanium compound.
[0244]
In order to manufacture the surface-treated steel sheet 81c illustrated in FIG.
8C, first, on the coated layer 82 of the surface-treated steel sheet obtained in the
method of the first or second embodiment, the chemical conversion treatment of
applying the treatment liquid including the silica, the silane coupling agent, and the
resin is performed, and the resuUant is dried and naturally cooled, thereby forming a
chemical conversion treatment film.
[0245] .
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Mb
In a case where the treatment liquid of the chemical conversion treatment
includes a zirconium compound, as the zirconium compound, generally well-known
compounds such as zirconyl ammonium carbonate, zircon hydrofluoric acid,
ammonium hexaflorozirconate, potassium hexafluorozirconate, sodium
hexafluorozirconate, zirconium(IV) acetylacetonate, a zirconium(IV) butoxide 1-
butanol solution, zirconium(IV) n-propoxide, and the like can be used.
In addition, in a case where the treatment liquid of the chemical conversion
treatment include a titanium compound, as the titanium compound, generally wellknown
compounds such as titanium hydrofluoric acid, titanium ammonium fluoride,
titanium potassium oxalate, titanium isopropoxide, isopropyl titanate, titanium
ethoxide, titanium 2-ethyl 1-hexanolate, titanium tetraisopropoxide, titanate tetra-nbutyl
potassium hexafluorotitanate, sodium hexafluorotitanate, and the like can be used.
[0246]
Next, on each surface of both surfaces of the steel sheet 81 where the coated
layer 82 and the chemical conversion treatment layer 17 are formed, the coloring
painted film layer 15 made from the primer-painted film layer 14 and the coloring
pigment layer 16 is formed in the same manner as the surface-treated steel sheet 81b
illustrated in FIG. 8B.
The surface-treated steel sheet 81c according to this embodiment has excellent
painting adhesion to the coated layer 82, has the chemical conversion treatment layer
17 formed between the coloring painted film layer 15 and the coated layer 82, and thus
has extremely high corrosion resistance and workability.
[0247]
(Example 1)
[Examples ml to m73. Comparative Examples xl, x5 to xl5]
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Surface-treated steel sheets were formed by the method described as follows
by using the coating apparatus illustrated in FIG. 2.
In a coating bath in a fluidized states in which the coating bath having the
coating bath composition, pH, and temperature shovra in Tables 1 to 3 was discharged
from the discharge port 2c, supplied from the supply port 2d, and circulated at an
average flow rate shown in Tables 1 to 3, a steel sheet as the cathode shown in Tables 1
to 3 was dipped. Using the material shown in Tables 1 to 3 as the anode, the coated
layers in Examples ml to m73, and Comparative Examples xl, x5 to xl5, each of
which included zmc and vanadium on the surface of the steel sheet (in Comparative
Example 1, only zinc was included) were formed by the electro coating method at a
current density for a time (electro deposition time) shown in Tables 1 to 3.
In addition, as the steel sheet, SPCD having a sheet thickness of 0.8 mm for
drawing a general cold-rolled steel sheet described in JIS G 3141 was used.

[Designation of Document] CLAIMS
[Claim 1]
A surface-treated steel sheet comprising:
a steel sheet; and
a coated layer which is formed on one surface or both surfaces of the steel
sheet and includes zinc and vanadium,
wherein the coated layer has a vanadium content of 1% or higher and 20% or
less and a coating weight of 3 g/m^ or higher and 40 g/m^ or less, and has a plurality of
dendritic arms that are grown in a thickness direction of the steel sheet, and
a ratio x/y of a content x of the vanadium that is present outside the arms to a
content y of the vanadium that is present inside the arms is 1.1 or higher and 3.0 or less
in terms of vanadium element.
[Claim 2]
The surface-treated steel sheet according to claim 1,
wherein the coated layer has an emissivity of 0.30 or higher and 0.95 or less
in a region where a wave number measured under a condition of a surface temperature
of 100°C is 600 to 3000 cm-^
[Claim 3]
The surface-treated steel sheet according to claim 1 or 2,
wherein a surface roughness of the coated layer is 1.0 |j.m or higher and 4.0
fxm or less in terms of center-line average roughness Ra specified in JIS B 0601:2001.
[Claim 4]
The surface-treated steel sheet according to claim 1 or 2,
wherein one or more layers of films are further formed on the coated layer.
[Claims]
.SI
The surface-treated steel sheet according to claim 4,
wherein the film contains an organic resin.
[Claim 6]
The surface-treated steel sheet according to claim 5,
wherein the film is a resin film, and contains:
5 to 50 parts by mass of metal oxide particles with respect to 100 parts by
mass of a solid content of the resin film; and
0.1 to 3 0 mass% of a lubricant with respect to 100 mass% of the solid content
of the resin film.
[Claim 7]
The surface-treated steel sheet according to claim 5,
wherein the organic resin has at least one type of a carboxyl group, a hydroxyl
group, a sulfonic acid group, and a silanol group in its structure, and includes:
a polyester resin containing a sulfonic acid group;
a curing agent; and
a coloring pigment containing carbon black.
[Claim 8]
The surface-treated steel sheet according to claim 4,
wherein the film is obtained by applying and drying a water-based metal
surface treatment agent containing a silane coupling agent onto the steel sheet.
[Claim 9]
The surface-treated steel sheet according to claim 8,
wherein the film fiirther contains an inhibitor component which essentially
includes a fluorometal complex compound having at least one type selected from
titanium and zirconium.
'Hav -
[Claim 10]
The surface-treated steel sheet according to claim 8,
wherein the fikn is a composite film including:
a polyether polyurethane resin; and
a coloring pigment containing carbon black.
[Claim 11]
The surface-treated steel sheet according to claim 5,
wherein the film is a coloring painted film layer including a coloring pigment
layer.
[Claim 12]
The surface-treated steel sheet according to claim 11,
wherein the coloring painted film layer includes a primer-painted film layer,
and
the primer-painted film layer is formed between the coated layer and the
coloring pigment layer and includes a rust-preventive agent.
[Claim 13]
The surface-treated steel sheet according to claim 11,
wherein the coloring painted film layer is formed on the coated layer to be in
contact therewith.
[Claim 14]
The surface-treated steel sheet according to claim 11,
wherein a chemical conversion treatment layer is further included between the
coloring painted fihn layer and the coated layer.
[Claim 15]
A method of manufacturing a surface-treated steel sheet, the method
yficomprising:
a coating process of forming a coated layer that includes zinc and vanadium
on a surface of a steel sheet by an electro coating method,
wherein, in the coating process, the coated layer is formed by dipping the steel
sheet in a coating bath, and performing an electro deposition at a current density in the
coating bath of 20 to 150 A/dm^ for a time of 1 second or longer and 30 seconds or less,
the coating bath contains a zinc compound and a vanadium compound.
contains at least one type of vanadium ions and vanadyl ions at a total content of 0.01
mol/1 or higher and less than 1.0 mol/1, and has a content of nitric acid ions limited to
be less than 0.0005 mol/1, and the coating bath is at least one of a circulated coating
bath or a coating bath obtained by moving the steel sheet in the coating bath to cause
the coating bath to be fluidized relative to the steel sheet, and
the coated layer has a vanadium content of 1% or higher and 20% or less and
a coating weight of 3 g/m^ or higher and 40 g/m^ or less.
[Claim 16]
The method of manufacturing a surface-treated steel sheet according to claim
15,
wherein an average flow rate of the coating bath in a coating tank is in a range
of20to300m/min.
[Claim 17]
The method of manufacturing a surface-treated steel sheet according to claim
15 or 16,
wherein the coating bath includes sodium ions at a content of 0.1 moM or
higher and 4.0 mol/1 or less.
[Claim 18]
^
The method of manufacturing a surface-treated steel sheet according to claim
15 or 16,
wherein the coating bath includes nickel ions at a content of 0.01 mol/1 or
higher and 1.0 mol/1 or less.