#

[Document Type] SPECIFICATION
[Title of the Invention] PAINTED PLATED-STEEL
[Technical Field]
[0001]
The present invention relates to a painted plated-steel.
Priority is claimed on Japanese Patent Application No. 2011 -182890, filed on August24, 2011 and Japanese Patent Application No. 2011-182830, filed on August 24, 2011, and the contents of which are incorporated herein by reference. [Background Art]
[0002]
In the related art, a hot-dip Zn-Al plated steel has been widely used for building materials, automobile materials, and materials for home electric appliances. Among products using such a hot-dip Zn-Al plated steel, a high aluminum (25 mass% to 75 mass%)-zinc alloy plated steel sheet represented by a 55% aluminum-zinc alloy plated steel sheet (Galvalume Steel Sheet (registered trademark)) is superior in corrosion resistance as compared to an ordinary hot-dip galvanized steel sheet. Therefore, a demand for the hot-dip Zn-Al plated steel has been increased. In addition, recently, since further improvement in corrosion and workability has been required particularly for building materials, techniques of adding Mg or the like to a plating layer to improve the corrosion resistance and the like of a hot-dip Zn-Al plated steel have been studied (refer to Patent Documents 1 to 4).
[0003]
However, in a high aluminum-zinc alloy steel sheet containing Mg, wrinkling is likely to occur on a surface of a plating layer, which causes deterioration in surface appearance. Further, steep protrusions are fonned on the surface of the plating layer
1

#

by this wrinkling. Therefore, when the plating layer is subjected to a chemical conversion treatment to form a chemical treatment layer or is subjected to coating or the like to form a plating layer, the thickness of the chemical treatment layer or the plating layer is likely to be non-uniform. As a result, there is a problem in that an effect of improving the corrosion resistance of a plated steel sheet obtained by coating or the like caimot be sufficiently exhibited.
[0004]
For example. Patent Document 1 discloses an Al-based hot-dip Al-Si-Mg-Zn plated steel sheet. A surface of this steel sheet includes a hot-dip plating layer that contains 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, and a balance consisting of Al and unavoidable impurities. Patent Document 1 discloses that the hot-dip plating layer may further contain 0.002 mass% to 0.08 mass% of Be and 0 mass% to 0.1 mass% of Sr. Ahernatively, the hot-dip plating layer may contain 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, 0.003 mass% to 0.05 mass% of Be. and 0 mass% to 0.1 mass% of Sr; may contain 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, 0 mass% to 0.003 mass% of Be, and 0.07 mass% to 1.7 mass% of Sr; may contain 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, 0 mass% to 0.003 mass% of Be, and 0.1 mass% to 1.0 mass% of Sr; may contain 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, 0.003 mass% to 0.08 mass% of Be. and 0.1 mass% to 1.7 mass% of Sr; or may contain 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, 0.003 mass% to 0.05 mass% of Be. and 0.1 mass% to 1.0 mass% of Sr.
[0005]

In the technique disclosed in Patent Document 1, Mg is added to a plating layer to improve the corrosion resistance of a hot-dip plated steel. However, wrinkling is likely to occur on the plating layer due to the addition of Mg. Patent Document 1 also discloses a technique of adding Sr or Be to a plating layer to suppress oxidation of Mg, thereby suppressing wrinkling. However, wrinkling is not sufficiently suppressed.
[0006]
It is difficult to sufficiently remove such wrinkles formed on the plating layer even with temper rolling and the like, and the wrinkles cause deterioration in the appearance of a hot-dip plated steel.
[0007]
In addition, in the high aluminium (25 to 75 mass%)-zinc alloy plated steel sheet according to the related art, although the durability of the plating layer (corrosion rate of the plating layer) and red rust resistance (a property of suppressing red rust generated from the steel sheet), or the red rust resistance and coating film blistering resistance of a cut end surface portion of the painted plated-steel sheet have been improved, there is no consideration for an improvement in the coiTOsion resistance of a scratched portion of the painted surface and a worked portion in which the base steel is deformed (a performance of suppressing the degradation in the appearance caused by corrosion of the plating layer and the occurrence of white rust (the white rust resistance of the plating layer), or a performance of suppressing the swelling of the painted coating film caused by a corrosion reaction). Particularly, there is no consideration for an improvement in the white rust resistance in a case of heating during use and in a case of UV irradiation during long-term use. [Prior Art Document]

f

[Patent Document]
[0008]
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. Hll-279735
[Patent Document 2] Japanese Patent No. 3718479
[Patent Document 3] PCT hitemational Publication No. WO2008/025066
[Patent Document 4] Japanese Unexamined Patent Application, First Publication No. 2007-284718 [Disclosure of the Invention] [Problems to be Solved by the Invention]
[0009]
The present invention has been made taking the foregoing circumstances into consideration. An object thereof is to provide a painted plated-steel in which the corrosion resistance of a scratched portion of a painted surface and a worked portion with a deformed base steel is good, in which white rust resistance is good in a case of heating and in a case where a base treatment layer and a plating layer are exposed from a cut end surface, a scratched portion, or the like during long-term use and thus are irradiated with ultraviolet light, and in which a good appearance is provided without an appearance failure caused by the plating layer. [Means for Solving the Problem]
[0010]
The inventors had considered a problem of appearance deterioration in the surface of the above-described painted plated material as follows. During a hot-dip plating treatment in which a hot-dip plating bath containing Mg is used. Mg is an element that is more likely to be oxidized than the other elements constituting the
4 -

plating layer, and thus Mg reacts with oxygen in the air and generates a Mg-based oxide on the surface layer of a hot-dip plating metal that adheres to the steel. Accordingly, Mg thickens on the surface layer of the hot-dip plating metal and formation of a Mg-based oxide film (a film made of oxides of metals including Mg) on the surface layer of the hot-dip plating metal is accelerated. In a process in which the hot-dip plating metal is cooled and solidifies, the Mg-based oxide film is formed before the solidification of the inside of the hot-dip plating metal is completed, and thus a difference in fluidity occurs between the surface layer and the inside of the hot-dip plating metal. Therefore, it is thought that even tjiough the inside of the hot-dip plating metal flows, the Mg-based oxide film on the surface layer thereof does not follow, and in a case where wrinkles and deflection generated as a result cannot be covered by coating performed on the upper layer, appearance failure occurs.
[0011]
Therefore, the inventors had intensively researched to suppress the difference in fluidity in the hot-dip plating metal during the hot-dip plating treatment as described above and had found means to suppress appearance deterioration such as wrinkles and deflection.
[0012]
Moreover, in addition to a coated base treatment for a hot-dip plated material capable of suppressing degradation in white rust resistance of a worked portion after being painted, which is caused by the degradation in the workability of the plating layer that occurs due to the above problem, a coated base treatment for a hot-dip plated material capable of suppressing the occurrence of white rust that occurs due to a sacrificial protection action of Zn or Mg in the plating metal and that is likely to occur particularly in a worked part, of suppressing white nist that is likely to occur in a case
- 5 -

of heating and in a case where a base treatment layer and a plating layer are exposed from a cut end surface, a scratched portion, or the like during long-term use and of thus are irradiated with ultraviolet light, and thus holding a beautiful appearance over a long period of time have been intensively researched, and as a result, the present invention had been completed.
[0013]
That is, the gist of the present invention is described along with exemplary embodiments as follows.
(1) According to an aspect of the present invention, a painted plated-steel includes: a steel; and a coating material that is provided on a surface of the steel, in which the coating material includes, in an order from the steel, a plating layer, a coated base treatment layer that is formed on a surface of the plating layer, and an organic coating layer that is formed on a surface of the coated base treatment layer, the plating layer contains Al, Zn, Si, and Mg as constituent elements in which an Al content is 25 mass% to 75 mass% and a Mg content is 0.1 mass% to 10 mass%, the plating layer contains 0.2 vol% to 15 vol% of a Si-Mg phase, a mass ratio of Mg in the Si-Mg phase to a total amount of Mg in the plating layer is 3% to 100%, the coated base treatment layer contains an organic resin and an organosilicon compound, the organosilicon compound has an alkylene group, a siloxane bond, and a crosslinkable functional group expressed by -SiR'R^R'', each of two of R', R^, and R^ is an alkox;^' group or a hydroxy group, the remaining one of R', R^, and R^ is an alkoxy group, a hydroxy group, or a methyl group, the organosilicon compound accounts for 2 to 1500 parts by mass with respect to 100 parts by mass of the organic resin, and a thickness of the organic coating layer is 0.2 to 100 i^m.
[0014]

(2) In the painted plated-steel described in (1), a Mg content in any region
having a diameter of 4 mm and a depth of 50 nm inside an outermost layer, which is
located at a depth of 50 nm from the surface of the plating layer, may be 0 mass% to
less than 60 mass%.
[0015]
(3) In the painted plated-steel described in (1) or (2), the plating layer may
fiirther contain 0.02 mass% to 1.0 mass% of Cr as a constituent element.
[0016]
(4) In the painted plated-steel described in any one of (1) to (3). a ratio of the
Si-Mg phase on the surface of the plating layer may be 0% or higher and 30% or less
in terms of area ratio.
[0017]
(5) In the painted plated-steel described in any one of (1) to (4), the coated
base treatment layer may contain one or more types selected from a zirconium
compound and a titanium compound.
[0018]
(6) In the painted plated-steel described in (5), in the coated base treatment
layer, one or more types selected from the zirconium compound and the titanium
compound may account for 50 to 3333 parts by mass with respect to 100 parts by mass
of the organic resin.
[0019]
(7) In the painted plated-steel described in (5), in the coated base treatment
layer, one or more types selected from the zirconium compound and the titanium
compound may account for 1 to 50 parts by mass with respect to 100 parts by mass of
the organic resin.

[0020]
(8) In the painted plated-steel described in any one of (1) to (7), the coated
base treatment layer may further contain 0.5 to 100 parts by mass of silica with respect
to 100 parts by mass of the organic resin.
[0021]
(9) In the painted plated-steel described in any one of (1) to (8), the coated
base treatment layer may fiirther contain 0.5 to 40 parts by mass of a phosphoric acid
compound with respect to 100 parts by mass of the organic resin.
[0022]
(10) In the painted plated-steel described in any one of (1) to (9), the coated
base treatment layer may further contain 1 to 50 parts by mass of tannin, tarmic acid, or
tannate with respect to 100 parts by mass of the organic resin.
[0023]
(11) In the painted plated-steel described in any one of (1) to (10), the coated
base treatment layer may further contain 0.5 to 10 parts by mass of a fluoride having
etching ability with respect to 100 parts by mass of the organic resin.
[0024]
(12) In the painted plated-steel described in any one of (1) to (11), the organic
coating layer may be constituted by two layers of a lower layer containing a corrosion-
resistant pigment and an upper layer which is colored.
[0025]
(13) In the painted plated-steel described in any one of (1) to (12), an
adhesion amount of the painted base treatment layer may be 10 to 2000 mg/m^.
[Effects of the Invention]
8 -

[0026]
According to the aspect described in (1) to (13), a painted plated-steel in which the corrosion resistance of a scratched portion of a painted surface and a worked portion with a deformed base steel is good, in which white rust resistance is good in a case of heating and in a case of ultraviolet light irradiation in a long-term use, and in which the occurrence of wrinkles and deflection on the surface is suppressed and thus an appearance is good is provided.
[Brief Description of the Drawing]
[0027]
FIG. 1 is a schematic diagram illustrating an example of a hot-dip plating treatment apparatus in an embodiment of the present invention.
FIG. 2 is a partial schematic diagram illustrating another example of the hot-dip plating treatment apparatus.
FIG. 3 A is a schematic diagram illustrating an example of a heating device used for an over-aging treatment in the embodiment of the present invention.
FIG. 3B is a schematic diagram illustrating an example of a heat insulation container for the over-aging treatment in the embodiment of the present invention.
FIG. 4A is an image obtained by taking a cut surface of a hot-dip plated steel sheet obtained at a level of M5 of Examples using an electron microscope.
FIG. 4B is a graph showing an element analysis result of a Si-Mg phase at the level of M5 of Examples.
FIG. 5 A is a graph showing a result of analysis of a plating layer in a depth direction by a glow discharge-optical emission spectrometer at the level of M5 of Examples.

FIG. 5B is a graph showing a result of analysis of the plating layer in the depth direction by the glow discharge-optical emission spectrometer at a level of M50 of Examples.
FIG. 6 is an image obtained by taking a surface of the plating layer in the hot-dip plated steel sheet obtained at the level of M5 of Examples using an electron microscope.
FIG. 7A shows a photograph of an appearance of the plating layer taken at the level of M5 of Examples.
FIG. 7B shows a photograph of the appearance of the plating layer taken at a level of MIO of Examples.
FIG. 8 A shows an optical micrograph of the appearance of the plating layer taken at a level of M62 of Examples.
FIG. 8B shows an optical micrograph of the appearance of the plating layer taken at the level of M5 of Examples.
FIG. 9 shows a photograph of the appearance of the plating layer taken at the level of M50 of Examples.
FIG. 10 is a graph showing an evaluation result of an over-aging treatment performed on the hot-dip plated steel sheet at the levej of M5 of Examples.
FIG. 11A is an example of a schematic diagram illustrating a layer structure of a painted plated-steel of the embodiment of the present invention.
FIG. 1 IB is an example of a schematic diagram illustrating a layer structure of the painted plated-steel of the embodiment of the present invention.
FIG. lie is an example of a schematic diagram illustrating a layer structure of the painted plated-steel of the embodiment of the present invention.
FIG. IID is an example of a schematic diagram illustrating a layer structure of
10

the painted plated-steel of the embodiment of the present invention.
FIG. HE is an example of a schematic diagram illustrating a layer structure of the painted plated-steel of the embodiment of the present invention.
FIG. 1 IF is an example of a schematic diagram illustrating a layer structure of the painted plated-steel of the embodiment of the present invention.
FIG. 11G is an example of a schematic diagram illustrating a layer structure of the painted plated-steel of the embodiment of the present invention.
FIG. 11H is an example of a schematic diagram illustrating a layer structure of the painted plated-steel of the embodiment of the present invention. [Embodiments of the Invention]
[0028]
Hereinafter, an embodiment used to carry out the present invention will be described.
[0029] [Painted Plated-Steel]
A painted plated-steel according to this embodiment includes a steel 1 and a coating material 29 on the surface of the steel 1 as illustrated in FIGS. 11A to 1IH. The coating material 29 includes, in order from the steel 1, an aluminium-zinc alloy plating layer 23 (hereinafter, referred to as a plating layer 23), a painted base treatment layer 24 on the surface of the plating layer 23, and an organic coating layer 25 on the surface of the painted base treatment layer 24. That is, the plating layer 23 is plated on the surface of the steel 1, and the painted base treatment layer 24 and the organic coating layer 25 are ftirther plated sequentially on the upper layer thereof As the steel 1, various members such as a thin steel sheet, a thick steel sheet, a die steel, a steel tube, and a steel wire may be employed. That is, the shape of the steel 1 is not
- 11

particularly limited. The plating layer 23 is formed by a hot-dip plating treatment.
[0030] [Plating layer 23]
The plating layer 23 contains Al, Zn, Si, and Mg as constituent elements. An Al content in the plating layer 23 is 25 mass% to 75 mass%. A Mg content in the plating layer 23 is 0.1 mass% to 10 mass%. Accordingly, the corrosion resistance particularly on the surface of the plating layer 23 is improved by Al, edge creep particularly on a cut end surface of the hot-dip plated steel is suppressed by the sacrificial corrosion preventing action of Zn, and thus high corrosion resistance is imparted to the hot-dip plated steel. Further, excessive alloying between Al in the plating layer 23 and the steel 1 is suppressed by Si, and deterioration in the workability of the hot-dip plated steel caused by an alloy layer 26 (described below) that is interposed between the plating layer 23 and the steel 1 is suppressed. Furthermore, the plating layer 23 contains Mg which is less noble than Zn such that the sacrificial corrosion preventing action of the plating layer 23 is strengthened and the corrosion resistance of the hot-dip plated steel is further improved.
[0031]
The plating layer 23 contains 0.2 vol% to 15 vol% of Si-Mg phase. The Si-Mg phase is a phase composed of an intermetallic compound between Si and Mg and is dispersed in the plating layer 23.
[0032]
A volume ratio of the Si-Mg phase in the plating layer 23 is equivalent to a volume ratio of the Si-Mg phase in a cut surface obtained by cutting the plating layer 23 in a thickness direction thereof The Si-Mg phase in the cut surface of the plating layer 23 can be clearly observed through an electronic microscope. Accordingly, by
12 -

measuring an area ratio of the Si-Mg phase in the cut surface, the volume ratio of the Si-Mg phase in the plating layer 23 can be indirectly measured.
[0033]
As the volume ratio of the Si-Mg phase in the plating layer 23 is increased, wrinkling on the plating layer 23 is suppressed. The reason is considered to be as follows. In a process of cooling a hot-dip plating metal to be solidified and thereby to form the plating layer 23 during the production of the hot-dip plated steel, the Si-Mg phase is precipitated in the hot-dip plating metal before the hot-dip plating metal is completely solidified. This Si-Mg phase suppresses the flow of the hot-dip plating metal. The volume ratio of the Si-Mg phase is more preferably 0.2 vol% to 10 vol% and still more preferably 0.4 vol% to 5 vol%.
[0034]
The plating layer 23 is composed of the Si-Mg phase and the other phases containing Zn and Al. The phases containing Zn and Al are mainly composed of an a-Al phase (dendritic structure) and a Zn-Al-Mg eutectic phase (indendritic structure). Depending on the composition of the plating layer 23, the phases containing Zn and Al may further contain various phases such as a phase (Mg-Zn2 phase) composed of Mg-Zn2, a phase (Si phase) composed of Si, and a phase (Fe-Al phase) composed of a Fe-Al intermetallic compound. The phases containing Zn and Al occupy regions other than the Si-Mg phase in the plating layer 23. Accordingly, a volume ratio of the phases containing Zn and Al in the plating layer 23 is preferabl}' in a range from 99.8 vol% to 85 vol%, more preferably in a range from 99.8 vol% to 90 vol%, and still more preferably in a range from 99.6 vol% to 95 vol%.
[0035]
A mass ratio of Mg in the Si-Mg phase to the total amount of Mg in the
13

plating layer 23 is 3% to 100%. Mg which is not contained in the Si-Mg phase is contained in the phases containing Zn and Al. Regarding the phases containing Zn and Al, Mg is contained, for example, in the a-Al phase, in the Zn-Al-Mg eutectic phase, in the Mg-Zn2 phase, and in a Mg-containing oxide film which is formed on the plating surface. When Mg is contained in the a-Al phase, Mg is solid-soluted in the a-Al phase.
[0036]
The mass ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 can be calculated on the assumption that the Si-Mg phase contains the stoichiometric composition of MgaSi. Actually, the Si-Mg phase may contain a small amount of elements other than Si and Mg such as Al, Zn, Cr, and Fe. and a composition ratio of Si and Mg in the Si-Mg phase may be slightly different from the stoichiometric composition. However, it is extremely difficult to strictly determine the amount of Mg in the Si-Mg phase in consideration of the above-described points. Therefore, in the present invention, when the mass ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 is determined, it is assumed that the Si-Mg phase has the stoichiometric composition of MgiSi.
[0037]
The mass ratio R of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 is calculated according to the following expression (1).
R=100xAMg/(MxCMG/100) ... (1)
R represents the mass ratio (mass%) of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23; AMg represents the Mg content (g/m^) which is contained in the Si-Mg phase in the plating layer 23 per unit area of the plating layer 23 in a plan view; M represents the mass (g/m^) of the plating layer 23 per unit area of
14

|B

the plating layer 23 in a plan view; and CMG represents a total Mg content (mass%) in the plating layer 23. It should be noted that the mass M of the plating layer 23 per unit area of the plating layer 23 in a plan view refers to, by using a surface of a steel sheet as a reference, the mass of the plating layer 23 which is attached onto the unit area of the surface of the steel sheet.
[0038]
AMg is calculated according to the following expression (2).
AMg=V2xp2xa ... (2)
V2 represents the volume (m /m ) of the Si-Mg phase in the plating layer 23 per unit area of the plating layer 23 in a plan view. p2 represents the density of the Si-Mg phase, and the value thereof is 1.94x 10^ (gW). a represents the content mass ratio of Mg in the Si-Mg phase, and the value thereof is 0.63.
[0039]
V2 is calculated according to the following expression (3).
V2=V,xR2/100 ... (3)
Vi represents the total volume (m /m ) of the plating layer 23 per unit area of the plating layer 23 in a plan view, and R2 represents the volume ratio (vol%) of the Si-Mg phase in the plating layer 23.
[0040]
Vi is calculated according to the following expression (4).
VrM/pi ... (4)
pi represents the total density (gW) of the plating layer 23. The pi value is calculated by weight-averaging the densities at room temperature of the constitutional elements of the plating layer 23 based on the composition of the plating layer 23.
[0041]
15

#

In this embodiment, as described above, a high ratio of Mg in the plating layer 23 is contained in the Si-Mg phase. Therefore, the amount of Mg present on the surface of the plating layer 23 is small, and thus the formation of a Mg-based oxide film on the surface of the plating layer 23 is suppressed. Accordingly, the wrinkling of the plating layer 23 caused by a Mg-based oxide film is suppressed. As the ratio of Mg in the Si-Mg phase to the total amount of Mg is higher, wrinkling is suppressed. This ratio is more preferably higher than or equal to 5 mass%, still more preferably higher than or equal to 20 mass%, and yet still more preferably higher than or equal to 50 mass%. The upper limit of the ratio of Mg in the Si-Mg phase to the total amount of Mg is not particularly limited, and this ratio may be 100 mass%.
[0042]
In an outermost layer which is located at a depth of 50 nm from the surface of the plating layer 23, it is preferable that a Mg content in any region having a diameter (diameter of a measurement portion) of 4 mm and a depth of 50 nm be 0 mass% to less than 60 mass%. This Mg content in the outermost layer of the plating layer 23 is measured by glow discharge optical emission spectroscopy (GD-OES). That is, a more specific measurement method is as follows. Each detected glow discharge intensity derived from each element is converted into a mass ratio of the element by a known coefficient or a coefficient obtained from a measured value of a standard sample having a known composition. Meanwhile, a glow emission time corresponding to a depth of 50 nm is obtained from the standard sample. Then, it is determined whether or not the mass ratio into which a glow discharge intensity ratio of Mg is converted is 0 mass% to less than 60 mass% at any time during the emission time obtained from the standard sample.
[0043]
- 16

#

As the Mg content in the outermost layer of the plating layer 23 is decreased, wrinkling caused by a Mg-based oxide film is suppressed. In any region having a diameter of 4 mm and a depth of 50 nm inside the outermost layer of the plating layer 23, the Mg content is more preferably less than 40 mass%, still more preferably less than 20 mass%, and yet still more preferably less than 10 mass%.
[0044]
It is preferable that an area ratio of the Si-Mg phase on the surface of the plating layer 23 be less than or equal to 30%. When the Si-Mg phase is present in the plating layer 23, the Si-Mg phase is likely to be formed on the surface of the plating layer 23 in a thin network shape. When the area ratio of the Si-Mg phase is high, the appearance of the plating layer 23 is changed. When a dispersion state of the Si-Mg phase on the plating surface is non-uniform, non-uniformity in luster is observed by visual inspection in the appearance of the plating layer 23. This non-uniformity in luster is an appearance defect called running. When the area ratio of the Si-Mg phase on the surface of the plating layer 23 is lower than or equal to 30%. running is suppressed, and the appearance of the plating layer 23 is improved. Further, a small amount of the Si-Mg phase on the surface of the plating layer 23 is effective for maintaining the corrosion resistance of the plating layer 23 over a long period of time. When the precipitation of the Si-Mg phase on the surface of the plating layer 23 is suppressed, the amount of the Si-Mg phase precipitated on the inside of the plating layer 23 is relatively increased. Therefore, the amount of Mg on the inside of the plating layer 23 is increased. As a result, the sacrificial con-osion preventing action of Mg in the plating layer 23 is exhibited over a long period of time, and thus high corrosion resistance of the plating layer 23 is maintained over a long period of time. In order to improve the appearance of the plating layer 23 and maintain the corrosion
- 17

resistance of the plating layer 23, the area ratio of the Si-Mg phase on the surface of the plating layer 23 is more preferably lower than or equal to 20%, still more preferably lower than or equal to 10%, and yet still more preferably lower than or equal to 5%.
[0045]
As described above, the Mg content in the plating layer 23 is in a range from 0.1 mass% to 10 mass%). When the Mg content is less than 0.1 mass%, the corrosion resistance of the plating layer 23 is not sufficiently secured. When this Mg content is greater than 10 mass%, the effect of improving corrosion resistance is saturated, and dross is likely to be formed in a hot-dip plating bath 2 during the production of the hot-dip plated steel. The Mg content is more preferably greater than or equal to 0.5 mass% and still more preferably greater than or equal to 1.0 mass%. In addition, the Mg content is particularly preferably less than or equal to 5.0 mass% and still more preferably less than or equal to 3.0 mass%). The Mg content is particularly preferably in a range from 1.0 mass%) to 3.0 mass%.
[0046]
An Al content in the plating layer 23 is in a range from 25 mass% to 75 mass%. When this Al content is greater than or equal to 25 mass%, the Zn content in the plating layer 23 is not excessive, and the corrosion resistance of the surface of the plating layer 23 is secured. When this Al content is less than or equal to 75 mass%, the sacrificial corrosion preventing effect of Zn is exhibited, the hardening of the plating layer 23 is suppressed, and the workability of the hot-dip plated steel is increased. Further, it is preferable that the Al content be less than or equal to 75 mass% from the viewpoint of fiirther suppressing the wrinkling of the plating layer 23 by controlling the fluidity of a hot-dip plating metal not to be excessively low during
- 18 -

the production of the hot-dip plated steel. The Al content is particularly preferably greater than or equal to 45 mass%. In addition, the Al content is particularly preferably less than or equal to 65 mass%. The Al content is particularly preferably in a range from 45 mass% to 65 mass%.
[0047]
A Si content in the plating layer 23 is preferably in a range from 0.5 mass% to 10 mass% with respect to the Al content. When the Si content is greater than or equal to 0.5 mass% with respect to the Al content, excessive alloying between Al in the plating layer 23 and the steel 1 is sufficiently suppressed. When this content is greater than 10 mass%, the effect of Si is saturated, and dross is likely to be formed in the hot-dip plating bath 2 during the production of the hot-dip plated steel. The Si content is particularly preferably greater than or equal to 1.0 mass%. In addition, the Si content is particularly preferably less than or equal to 5.0 mass%. The Si content is particularly preferably in a range from 1.0 mass% to 5.0 mass%.
[0048]
Further, a mass ratio Si:Mg in the plating layer 23 is preferably in a range from 100:50 to 100:300. In this case, the formation of the Si-Mg layer in the plating layer 23 is particularly promoted, and the wrinkling of the plating layer 23 is further suppressed. This mass ratio Si:Mg is more preferably in a range from 100:70 to 100:250 and still more preferably in a range from 100:100 to 100:200.
[0049]
It is preferable that the plating layer 23 further contain Cr as a constitutional element. In this case, the growth of the Si-Mg phase in the plating layer 23 is promoted by the Cr, the volume ratio of the Si-Mg phase in the plating layer 23 is increased, and the ratio of Mg in the Si-Mg phase to the total amount of Mg in the
- 19

^p

plating layer 23 is increased. As a result, the wrinkling of the plating layer 23 is further suppressed. A Cr content in the plating layer 23 is preferably in a range from 0.02 mass% to 1.0 mass%. When the Cr content in the plating layer 23 is greater than 1.0 mass%, the above-described action is saturated, and dross is likely to be formed in the hot-dip plating bath 2 during the production of the hot-dip plated steel. The Cr content is particularly preferably greater than or equal to 0.05 mass%. In addition, the Cr content is particularly preferably less than or equal to 0.5 mass%. The Cr content is more preferably in a range from 0.07 mass% to 0.2 mass%.
[0050]
When the plating layer 23 contains Cr, it is preferable that the Cr content in the outermost layer, which is located at a depth of 50 nm from the surface of the plating layer 23, be 100 mass ppm to 500 mass ppm. In this case, the corrosion resistance of the plating layer 23 is further improved. The reason is considered to be as follows. When Cr is present in the outermost layer, a passive film is formed on the plating layer 23, and thus the anodic dissolution of the plating layer 23 is suppressed. The Cr content is preferably 150 mass ppm to 450 mass ppm and more preferably 200 mass ppm to 400 mass ppm.
[0051]
It is preferable that the alloy layer 26 containing Al and Cr be interposed between the plating layer 23 and the steel 1. In the embodiment, it is assumed that the alloy layer 26 is different from the plating layer 23. The alloy layer 26 may further contain various metal elements other than Al and Cr such as Mn, Fe, Co, Ni, Cu, Zn, and Sn as constitutional elements. When such an alloy layer 26 is present in the hot-dip plated steel, the growth of the Si-Mg phase in the plating layer 23 is promoted by Cr in the alloy layer 26, the volume ratio of the Si-Mg phase in the plating layer 23
- 20

%.

is increased, and the ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 is increased. As a result, the wrinkling and running of the plating layer 23 is further suppressed. In particular, it is preferable that a ratio of the Cr content in the alloy layer 26 to the Cr content in the plating layer 23 be 2 to 50. In this case, the growth of the Si-Mg phase near the alloy layer 26 in the plating layer 23 is promoted, which decreases the area ratio of the Si-Mg phase on the surface of the plating layer 23. As a result, running is further suppressed, and the corrosion resistance of the plating layer 23 is maintained over a longer period of time. The ratio of the Cr content in the alloy layer 26 to the Cr content in the plating layer 23 is more preferably 3 to 40 and still more preferably 4 to 25. The Cr content in the alloy layer 26 can be obtained by measuring a cross-section of the plating layer 23 using an energy dispersive X-ray analyzer (EDS).
[0052]
The thickness of the alloy layer 26 is preferably in a range from 0.05 |j,m to 5 l^m. When this thickness is greater than or equal to 0.05 |im. the above-described effect of the alloy layer 26 is effectively exhibited. When this thickness is less than or equal to 5 \im, deterioration in the workability of the hot-dip plated steel caused by the alloy layer 26 is prevented.
[0053]
When the plating layer 23 contains Cr, the corrosion resistance of the plating layer 23 after a treatment is improved. The reason is considered to be as follows. When the plating layer 23 is subjected to a strict treatment, cracks are initiated on the plating layer 23. At this time, water and oxygen are infiltrated into the plating layer 23 through the cracks, and an alloy in the plating layer 23 is directly exposed to corrosive factors. However, Cr which is present particularly in tlie surface of the
21

1$

plating layer 23 and Cr which is present in the alloy layer 26 suppress the corrosion reaction of the plating layer 23, thereby suppressing the expansion of corrosion originating from the cracks. Particularly, in order to improve the corrosion resistance of the plating layer 23 after a treatment, the Cr content in the outermost layer which is located at a depth of 50 nm from the surface of the plating layer 23 is preferably greater than or equal to 300 mass ppm and is particularly preferably in a range from 200 mass ppm to 400 mass ppm. In addition, particularly, in order to improve corrosion resistance of the plating layer 23 after a treatment, the ratio of the Cr content in the alloy layer 26 to the Cr content in the plating layer 23 is preferably higher than or equal to 20 and is particularly preferably in a range from 20 to 30.
[0054]
ft is preferable that the plating layer 23 further contain Sr as a constitutional element. In this case, the formation of the Si-Mg layer in the plating layer 23 is particularly promoted by Sr. Further, the formation of a Mg-based oxide film on the surface of the plating layer 23 by Sr is suppressed. The reason is considered to be that, by the Sr oxide film being preferentially formed before the formation of the Mg-based oxide film, the formation of the Mg-based oxide film is inhibited. As a result, the wrinkling of the plating layer 23 is ftirther suppressed. The Sr content in the plating layer 23 is preferably in a range from 1 mass ppm to 1000 mass ppm. When the Sr content is less than 1 mass ppm, the above-described action is not exhibited. When the Sr content is greater than 1000 mass ppm, the action of Sr is saturated, and dross is likely to be formed in the hot-dip plating bath 2 during the production of the hot-dip plated steel. The Sr content is particularly preferably greater than or equal to 5 mass ppm. In addition, the Sr content is preferably less than or equal to 500 mass ppm and more preferably less than or equal to 300 mass ppm. The Sr content is still
7? -

more preferably in a range from 20 mass ppm to 50 mass ppm.
[0055]
It is preferable that the plating layer 23 further contain Fe as a constitutional element. In this case, the formation of the Si-Mg layer on the plating layer 23 is particularly promoted by Fe. Further, Fe contributes to the refinement of the microstructure and spangle structure of the plating layer 23, which improves the appearance and workability of the plating layer 23. A Fe content in the plating layer 23 is preferably in a range from 0.1 mass% to 0.6 mass%. When the Fe content is less than 0.1 mass%, the microstructure and spangle structure of the plating layer 23 are coarsened, which deteriorates the appearance and workability of the plating layer 23. When the Fe content is greater than 0.6 mass%, the spangle structure of the plating layer 23 is excessively refined or disappears. As a result, the appearance is not improved by the spangle strticture, dross is likely to be formed in the hot-dip plating bath 2 during the production of the hot-dip plated steel, and the appearance of the plating layer 23 further deteriorates. The Fe content is particularly preferably greater than or equal to 0.2 mass%. In addition, the Fe content is particularly preferably less than or equal to 0.5 mass%. The Fe content is particularly preferably in a range from 0.2 mass% to 0.5 mass%. A flower-shaped structure appearing on the surface of the steel sheet 1 after plating is called the spangle structure.
[0056]
The plating layer 23 may further contain, as a constitutional element, an element selected from the group consisting of alkaline earth elements. Sc, Y, lanthanoid elements, Ti, and B.
[0057]
Alkaline earth elements (Be. Ca, Ba. Ra), Sc, Y, and lanthanoid elements (for
23

M

example. La, Ce, Pr, Nd, Pm, Sm, and Eu) exhibit the same action as that of Sr. The total content of these elements in the plating layer 23 is preferably less than or equal to 1.0 mass% by mass ratio.
[0058]
When the plating layer 23 contains at least one of Ti and B, the a-Al phase (dendritic structure) of the plating layer 23 is refined, and thus, the spangle structure is refined. Therefore, the appearance of the plating layer 23 is improved by the spangle structure. Further, the wrinkling of the plating layer 23 is further suppressed by at least one of Ti and B. The reason is considered to be that the Si-Mg phase is also refined by the action of Ti and B, this refined Si-Mg phase solidifies a hot-dip plating metal, and the flow of the hot-dip plating metal is effectively suppressed in a process of forming the plating layer 23. Further, due to the refinement of the plating structure, the concentration of stress in the plating layer 23 during bending is relaxed, the initiation of large cracks is suppressed, and the bendability of the plating layer 23 is further improved. In order to exhibit the above-described effects, the total content of Ti and B in the hot-dip plating bath 2 is preferably in a range of 0.0005 mass% to 0.1 mass% by mass ratio. The total ratio of Ti and B is particularly preferably greater than or equal to 0.001 mass%. The total ratio of Ti and B is particularly preferably less than or equal to 0.05 mass%. The total ratio of Ti and B is particularly preferably in a range from 0.001 mass% to 0.05 mass%.
[0059]
Zn constitutes a balance obtained by excluding constitutional elements other than Zn from all the constitutional elements of the plating layer 23.
[0060]
It is preferable that the plating layer 23 do not contain elements other than the
24 -

above-described elements as constitutional elements. Particularly, it is preferable that the plating layer 23 only contain Al, Zn, Si, Mg, Cr, Sr, and Fe or only contain Al, Zn, Si, Mg, Cr, Sr, Fe, and an element selected from the group consisting of alkaline earth elements, Sc, Y, lanthanoid elements, Ti, and B as constitutional elements. [0061]
In this case, it is needless to say that the plating layer 23 may contain unavoidable impurities such as Pb, Cd, Cu, and Mn. It is preferable that the content of the unavoidable impurities be small. It is particularly preferable that the total content of the unavoidable impurities be less than or equal to 1 mass% by mass ratio with respect to the plating layer 23.
[0062] [Painted Base Treatment Layer 24]
The painted base treatment layer 24 coated at the upper layer of the plating
layer 23 includes, as essential components, an organic resin, and an organosilicon
compound having an alkylene group, a siloxane bond, and a crosslinkable functional
group expressed by the following General Formula (X).
-SIR'RV ...(X)
In the formula, R\ R^, and R^ each independently represent an alkoxy group or a hydroxy group. In addition, any one of R', R^, and R'' may be substituted with a methyl group. That is, each of two of R', R^, and R^ is an alkoxy group or a hydroxy group, and the remaining one of R', R^, and R^ is an alkoxy group, a hydroxy group, or a methyl group. [0063]
The organic resin which is the essential component of the painted base treatment layer 24 has excellent barrier properties against corrosion factors (water,
- 25

#

oxygen, and the like), and has an excellent property of holding the Mg-based oxide film formed on the surface layer of the plating layer 23 and initial coiTOsion products of Zn and Mg that are produced by the sacrificial protection action of Zn and Mg of the plating layer 23. Moreover, the organic resin imparts flexibility to the painted base treatment layer 24 while enhancing adhesion between the painted base treatment layer 24 and the plating layer 23, and enables the painted base treatment layer 24 to follow the deformation of the plated steel. Therefore, the painted base treatment layer 24 that contains the organic resin prevents exfoliation, adhesion degradation, and the like of the organic coating layer 25 even in a site that is deformed because the painted plated-steel is worked, and thus has significant corrosion resistance, particularly excellent white rust resistance compared to a painted plated-steel without the painted base treatment layer 24, thereby exhibiting an effect of delaying the occurrence of red rust.
[0064]
The plating layer 23 of the present invention contains 25 to 75 mass% of Al and 0.2 to 15 volume% of the Si-Mg phase. As described above, as the volume ratio of the Si-Mg phase in the plating layer 23 is increased, the occurrence of wrinkles of the plating layer 23 is suppressed. On the other hand, since the Si-Mg phase is hard and brittle, cracks are likely to be generated during work compared to the plating layer 23 with no Si-Mg phase. Since the sacrificial protection action of Zn or Mg in the plating layer 23 is exhibited even when cracks are generated, red rust resistance is not damaged. However, white rust which is a corrosion product of Zn and Mg is likely to be generated in a site subjected to work. In addition, due to the generated cracks, the adhesion with the organic coating at the upper layer is degraded, and the organic coating of the worked portion even peels off and con^osion accelerating materials such
26

as water, oxygen, and salt easily come into contact with the plating layer 23, which is a factor for generating white rust. The organic resin which is the essential component of the painted base treatment layer 24 has a feature of imparting flexibility to the painted base treatment layer 24 and imparting excellent adhesion between the plating layer 23 and the organic coating at the upper layer. That is, since the painted plated-steel having the painted base treatment layer 24 has excellent followability to deformation (elongation and compression) of the steel caused by work, the site subjected to the work is less likely to be damaged by cracks, scratches, and the like over the entire organic coating. In addition, even when the organic coating is cracked, the organic coating at the position is less likely to peel off from the plated surface, and thus the appearance and corrosion resistance (particularly white rust resistance) can be maintained.
[0065]
On the other hand, the organosilicon compound which is the other essential component of the painted base treatment layer 24 also has excellent barrier properties against corrosion factors (water, oxygen, and the like) and an excellent property of holding the Mg-based oxide film formed on the surface layer of the plating layer 23 and initial corrosion products of Zn and Mg that are produced by the sacrificial protection action of Zn and Mg of the plating layer 23. Therefore, the painted base treatment layer 24 that contains the organosilicon compound has significant corrosion resistance, particularly excellent white rust resistance compared to a hot-dip plated steel without the organosilicon compound, thereby exhibiting an effect of delaying the occurrence of red rust.
[0066]
The organosilicon compound further has a feature of haxing an excellent
27 -

balance between flexibility and hardness. That is, the painted base treatment layer 24 that contains the organosilicon compound has excellent followability to deformation (elongation and compression) of the steel caused when the plated steel is worked, and thus the site subjected to the work is uniformly coated without damaging the painted base treatment layer 24 by cracks, scratches, and the like, thereby maintaining excellent corrosion resistance and contamination resistance. In addition, since the painted base treatment layer 24 has appropriate hardness, even when the organic coating layer 25 at the upper layer is scratched, an effect of preventing the scratch from propagating to the plating layer 23 can be expected.
[0067]
The organic resin and the organosilicon compound are cross-linked each other and form a denser coating, and thus barrier properties against corrosion factors (water, oxygen, and the like) and the enhancement of a property of holding the Mg-based oxide film formed on the surface layer of the plating layer 23 and initial corrosion products of Zn and Mg that are produced by the sacrificial protection action of Zn and Mg of the plating layer 23 can be expected.
[0068]
Hereinafter, the configyration of the painted base treatment layer 24 will be described.
[0069]
The organic resin is not hmited to specific types, and for example, a polyester resin, a polyurethane resin, an epoxy resin, an acrylic resin, a polyolefin resin, and modified bodies of the resins may be employed. As the organic resin, one type or two or more types of organic resins (not modified) may be mixed to be used, or one type or
- 28 -

two or more types of organic resins obtained by, in the presence of at least one type of organic resin, modifying at least one type of other organic resins may be mixed to be used.
[0070]
The polyester resin is not particularly limited, and for example, a resin obtained by condensation polymerization of a polyester raw material made of a polycarboxylic acid component and a polyol component may be used. In addition, a water-based resin obtained by dissolving or dispersing the obtained polyester resin in water may also be used.
[0071]
Examples of the polycarboxylic acid component include phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetra phthalic acid, methyltetrahydrophthalic anhydride, himic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride, flimaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, succinic anhydride, lactic acid, dodecenylsuccinic acid, dodecenylsuccinic anhydride, cyclohexane-l,4-dicarboxylic acid, and endic anhydride. As such a polycarboxylic acid component, one kind of the above-described components may be used, or plural kinds of the above-described components may be used.
[0072]
Examples of the polyol component include ethylene glycol, diethylene glycol, 1,3-propanediol, 1,2-propanediol, triethylene glycol, 2-methy 1-1.3-propanediol, 2,2-dimethyl-l,3-propanediol, 2-butyl-2-ethyl-L3-propanediol, 1.4-butanediol. 2-methyl-
29

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, hydrated bisphenol-A, dimer diol, trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol. As such a polyol component, one kind of the above-described components may be used, or plural kinds of the above-described components may be used.
[0073]
The polyurethane resin is not particularly limited, and examples thereof include resins obtained using, for example, a method including causing a polyol compound and a polyisocyanate compound to react with each other; and then extending the chain with a chain extender. The polyol compound is not particularly limited as long as it is a compound containing two or more hydroxyl groups per molecule, and examples thereof include polyether polyols such as ethylene glycol, propylene glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, glycerin, trimethylolethane, trimethylolpropane, polycarbonate polyol, polyester polyol, and bisphenol hydroxypropyl ether; polyester amide polyol; acryl polyol; polyurethane polyol; and mixtures of the above-described polyol compounds. The polyisocyanate compound is not particularly limited as long as it is a compound containing two or more isocyanate groups per molecule, and examples thereof include aliphatic isocyanates such as hexamethylene diisocyanate (HDI); alicyclic diisocyanates such as isophoron diisocyanate (IPDI); aromatic diisocyanates such as tolylene diisocyanate (TDI); aromatic diisocyanates such as diphenylmethane diisocyanate (MDI); and mixtures of the above-described polyisocyanate compounds. The chain extender is not particularly limited as long as it is a compound containing one or more active hydrogens in the molecules, and examples thereof include aliphatic
- 30 -

polyamines such as ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, and tetraethylenepentamine; aromatic polyamines such as tolylenediamine, xylylenediamine, and diaminodiphenylmethane; alicyclic polyamines such as diaminocyclohexylmethane, piperadine, 2,5-dimethylpiperadine, and isophoronediamine; hydrazides such as hydrazine, dihydrazide succinate, dihydrazide adipate, and dihydrazide phthalate; and alkanolamines such as hydroxyethyl diethylenetriamine, 2-[(2-aminoethyl)amino]ethanol, and 3-aminopropanediol. These compounds may be used alone or as a mixture of two or more kinds thereof.
[0074]
The epoxy resin is not particularly limited, and examples thereof include epoxy resin such as a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a hydrogenated bisphenol A type epoxy resin, a hydrogenated bisphenol F-type epoxy resin, a resorcin-type epoxy resin, and a novolac-type epoxy resin. In addition, other examples of the epoxy resin include water-based epoxy resins obtained by forced emulsifying the above-described epoxy resins with a surfactant; water-based epoxy resins obtained by causing the above-described epoxy resins to react with an amine compound such as diethanolamine or N-methylethanolamine and neutralizing the resultant with an organic acid or an inorganic acid; and water-based epoxy resins obtained by radical-polymerizing a high acid value acrylic resin in the presence of the above-described epoxy resins and neutralizing the resultant with ammonia or an amine compound.
[0075]
The acrylic resin is not particularly limited, and examples thereof include acrylic resins obtained by radical-polymerizing a (meth)acr}iic acid ester with a
- 31 -

(meth)acrylic acid in water using a polymerization initiator. Examples of the (meth)acrylic acid ester include alkyl (meth)acrylates such as ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-butyl (meth)acrylate; hydroxyalkyl (nieth)acrylates such as 2-hydroxyethyl (meth)acrylate; and alkoxysilane (meth)acrylates. The polymerization initiator is not particularly limited, and examples thereof include persulfates such as potassium persulfate, and ammonium persulfate; and azo compounds such as azobis cyanovaleric acid, and azobis isobutyronitrile. "(meth)acrylate" described herein refers to acrylate and methacrylate, and "(meth)acrylic acid" described herein refers to acrylic acid and methacrylic acid.
[0076]
The polyolefin resin is not particularly limited, and examples thereof include water-based resins obtained using a method including radical-polymerizing ethylene with an unsaturated carboxylic acid such as methacrylic acid, acrylic acid, maleic acid, fumaric acid, itaconic acid, or crotonic acid in a high-temperature and high-pressure environment; and neutralizing the resultant with ammonia or an amine compound, with a basic metal compound such as KOH, NaOH, or LiOH, or with ammonia or an amine compound containing the basic metal compound.
[0077]
In addition, the organic resin preferably contains a resin containing at least one type of functional group selected from an ester group, a urethane group, and a urea group in its structure in order to enhance corrosion resistance and scratch resistance as the painted plated-steel. In order to enhance the corrosion resistance as the painted plated-steel, it is important to uniformly coat the plated steel (excellent workability) without scratches such as cracks of the painted base treatment layer 24 even in a worked site and suppress permeability of corrosion factors. Furthermore, it is
32

important to increase the adhesion between the painted base treatment layer 24 and the plated surface. In order to realize the painted base treatment layer 24 as such, organic resin containing a specific resin structure is appropriately used as a film-forming component. Specifically, by introducing a functional group having a specific cohesive energy as described above into the resin structure of the organic resin, both the elongation and strength of the coating film are increased to a higher dimension, and adhesion and corrosion resistance can also be enhanced.
[0078]
The resin containing at least one functional group selected from the group consisting of an ester group, a urethane group, and a urea group in the resin structure is not particularly limited, and examples thereof include a polyester resin containing an ester group, a polyurethane resin containing a uretharle group, and a poiyurethane resin containing both a urethane group and a urea group. These resins may be used alone or as a mixture of two or more kinds. For example, a resin containing all of an ester group, a urethane group, and a urea group, which is obtained b\ mixing a polyester resin containing an ester group with a polyurethane resin containing both a urethane group and a urea group, may be used as the organic resin.
[0079]
The organosilicon compound is a organosilicon compound containing an alkylene group, a siloxane bond, and a crosslinkable functional group expressed by General Formula (X):
-SiR'R^R^ ...(X)
(In the formula, R , R , and R each independently represent an alkoxy group or a hydroxy group. In addition, any one ofR'.RlandR^ mav he substituted with a

methyl group. That is, each of two of R , R , and R is an alkoxy group or a hydroxy group, and the remaining one of R', R"^, and R'' is an alkoxy group, a hydroxy group, or a methyl group.), and enhances the adhesion between the painted base treatment layer 24 and the plated surface and the adhesion between the painted base treatment layer 24 and the organic coating at the upper layer. In addition, the organosilicon compound enables cross-linkage between the organic resins or between the organic resin and silica particles, thereby enhancing the strength of the painted base treatment layer 24 and a property of impeding permeation of corrosion accelerating materials such as water, oxygen, and sah.
[0080]
The organosilicon compound is not particularly limited as long as it contains an alkylene group, a siloxane bond, and a crosslinkable functional group expressed by the General Formula (X), and a compound that contains an alkylene group, a siloxane bond, and a crosslinkable functional group expressed by the General Fonnula (X) and is able to be stably present in an aqueous medium containing water as the main component is preferable. Furthermore, as the organosilicon compound, a compound which contains at least one type of crosslinkable functional groups selected from an amino group, an epoxy group, and a hydroxy group (different from that contained in the General Formula (X)) forms a denser film having a higher cross-link density and is thus preferable to enhance the corrosion resistance of the painted plated-steel. Furthermore, since the crosslinkable functional group has hydrophilicity, in a case where a paint composition for forming the painted base treatment layer 24 is a water-based paint, containing at least one type of crosslinkable functional groups selected from an amino group, an epoxy group, and a hydroxy group, is advantageous in enhancing the stability of the organosilicon compound in a water-based solvent. In
34

4m-

addition, in this specification, stability in a water-based solvent is referred to as being less likely to generate coagulation and sediment in a water-based solvent as time elapses, and being less likely to cause a phenomenon such as thickening or gelation.
[0081]
As the organosilicon compound, hydrolysis condensate of a silane coupling agent or the like may be exemplified. Specific examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3 -
methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyItrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane. 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, bis(trimethoxysilylpropyl)amine, 3-triethoxysilyl-N-(l ,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane. 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyItriethoxysilane. 3-isocyanatopropyltriethoxysilane, and bis(trimethoxysilyl)hexane. The silane coupling agents may be used singly or in a combination of two or more types thereof. [0082]
In addition, as the organosilicon compound, a compound obtained by a reaction between a silane coupling agent containing an amino group and a silane coupling agent containing an epoxy group is particularly preferable. By the reaction
35 -

between the amino group and the epoxy group and the reaction between the alkoxy silyl groups or between the partial hydrolysates thereof respectively contained in the silane coupling agent and the silane coupling agent, a denser film having a higher cross-link density can be formed, and accordingly, the corrosion resistance, scratch resistance, and contamination resistance of the painted hot-dip plated steel can fiarther be enhanced. As the silane coupling agent containing an amino group, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, or
bis(trimethoxysilylpropyl)amine may be exemplified, and as the silane coupling agent containing an epoxy group (BE), 3-glycidoxypropyltrimethoxysilane. 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, or 3-glycidoxypropylmethyldiethoxysilane are exemplary examples.
[0083]
In a case where the silane coupling agent containing an amino group is referred to as BA and the silane coupling agent containing an epoxy group is referred to as BE, a molar ratio BA/BE is preferably 0.5 or higher and 2.5 or less, and more preferably 0.7 or higher and 1.6 or less. When the molar ratio BA/BE is less than 0.5, film-forming properties are degraded, and there may be cases where the effect of enhancing corrosion resistance becomes insufficient. When the molar ratio BA/BE is higher than 2.5, water resistance is degraded, and there may be cases Vvhere the effect of enhancing corrosion resistance becomes insufficient.
[0084]
The number average molecular weight of the organosilicon compound is preferably 1000 or higher and 10000 or less, and more preferabl\' 2000 or higher and
36

10000 or less. A method of measuring the molecular weight mentioned here is not particularly limited, and any of direct measurement according to a TOF-MS method and conversion measurement according to chromatography may be used. When the number average molecular weight is less than 1000, the water resistance of the formed film is degraded, and there may be cases where alkali resistance and corrosion resistance are degraded. In contrast, when the number average molecular weight is higher than 10000, it is difficult to dissolve or disperse the organosilicon compound in an aqueous medium containing water as the main component, and there may be cases where the storage stability of the paint composition for forming the painted base treatment layer is degraded. The number average molecular weight of the organosilicon compound is preferably 2000 or higher and 5000 or less.
[0085] [Painted Base Treatment Layer 24]
The painted base treatment layer 24 coated at the upper layer of the plating layer 23 may include one or more types selected from a zirconium compound and a titanium compound as film-forming components in addition to the organic resin and the organosilicon compound. [0086]
One or more types selected from the zirconium compound and the titanium compound as the components of the painted base treatment layer 24 has not only excellent barrier properties (corrosion resistance) against corrosion factors (water, oxygen, and the like) but also excellent heat resistance and durability against energy rays such as UV light because the components having excellent banner properties form inorganic bonds. In addition, the adhesion between Al oxides and Mg oxides on the surface of the plating layer 23 is good. That is, the hot-dip plated steel coated with
)1

the painted base treatment layer 24 containing one or more types selected from the zirconium compound and the titanium compound as the film-fonning components has good white rust resistance, particularly white rust resistance in a case of heating and in a case of UV irradiation in a long-term use, and due to high adhesion to the oxides on the surface of the plating layer, holds the painted base treatment layer 24 and the organic coating layer 25 at the upper layer over a long period of time, thereby maintaining the white rust resistance for a long period of time.
[0087]
Here, the configuration of the painted base treatment layer 24 will be described.
[0088]
The zirconium compound and the titanium compound contained in a treatment agent for forming the painted base treatment layer 24 are not particularly limited. For example, as the zirconium compound, zirconium nitrate, zirconium acetate, zirconium sulfate, ammonium zirconium carbonate, potassium zirconium carbonate, sodium zirconium carbonate, zirconium acetate, zirconium hydrofluoric acid, or a salt thereof may be employed. Among the zirconium compounds, a zirconium compound containing zirconium hydrofluoric acid or a salt thereof, or zirconium carbonate complex ions is preferable from the viewpoint of corrosion resistance. The zirconium compound containing zirconium carbonate complex ioins is not particularly limited, and for example, an ammonium salt, a potassium salt, or a sodium salt of zirconium carbonate complex ions [Zr(C03)2(OH)2]2' or [Zr(C03)3(OH)]3".
[0089]
In addition, as the titanium compound, for example, titanium potassium
38 -

oxalate, titanyl sulfate, titanium chloride, titanium lactate, titanium isopropoxide, isopropyl titanate, titanium ethoxide, titanium 2-ethyl-l-hexanolate, tetraisopropyl titanate, tetra-n-butyl titanate, titania sol, titanium hydrofluoric acid, or a salt thereof may be employed. Among the titanium compounds, titania sol. titanium lactate, titanium hydrofluoric acid, or a salt thereof is preferable from the viewpoint of corrosion resistance.
[0090]
The amount of the zirconium compound and the titanium compound being blended is preferably 1 to 3333 parts by mass with respect to 100 parts by mass of the organic resin in order to enhance the corrosion resistance of scratched portions. When the blending amount of the zirconium compound and the titanium compound is high, the ratio of inorganic components in the base treatment component is increased, the painted base treatment layer 24 is weakened, and thus there may be cases where the film adhesion is degraded during work and corrosion resistance is degraded. Therefore, in a case where the corrosion resistance of the worked portion is important, 1 to 50 parts by mass with respect to 100 parts by mass of the organic resin may be a more preferable blending amount. When the amount of the zirconium compound and the titanium compound is less than 1 part by mass, barrier properties against corrosion factors (corrosion resistance) are poor, and thus the corrosion resistance of the cut end surface of the painted plated-steel becomes insufficient in a case where the film is scratched or the like. In addition, there may be cases where heat resistance and durability against energy rays such as UV light become insufficient. When the amount exceeds 3333 parts by mass, the base treatment layer becomes brittle, and the coating adhesion of the bent portion of the film is degraded. Therefore, there may be cases where the corrosion resistance of the bent portion becomes insuftlcient.
- 39

#

[0091]
A method of producing the organosilicon compound is not particularly limited, and for example, a method of obtaining an aqueous liquid of hydrolysis condensates by dissolving or dispersing a silane coupling agent in water and stiiring the resultant at a predetermined temperature for a predetermined time, a method of obtaining an aqueous liquid by dissolving or dispersing an organosilicon compound such as hydrolysis condensates of a silane coupling agent in water, or a method of obtaining an alcohol-based liquid by dissolving an organosilicon compound such as hydrolysis condensates of a silane coupling agent in an alcoholic organic solvent such as methanol, ethanol, or isopropanol may be employed. In order to dissolve or disperse the silane coupling agent or hydrolysis condensates thereof in a water-based medium, an acid, an alkah, an organic solvent, a surfactant, or the like may be appropriately added. Particularly, it is preferable from the viewpoint of storage stability to adjust a pH to 3 to 6 by adding an organic acid. The solid content concentration of the aqueous liquid or the alcohol-based liquid of the organosilicon compound is preferably 25 mass% or less. When the solid content concentration of the organosilicon compound (B) exceeds 25 mass%, there may be cases where the storage stability of the aqueous liquid or the alcohol-based liquid thereof is degraded. [0092]
The content of the organosilicon compound is 2 to 1500 parts by mass with respect to 100 parts by mass of the organic resin. When the content is less than 2 parts by mass, the effect of enhancing corrosion resistance cannot be obtained, and there may be cases where the storage stability of the paint composition used to form the painted base treatment layer 24 is degraded. In contrast, when the content exceeds 1500 parts by mass, there may be cases where sufficient corrosion resistance
40 -

cannot be obtained.
[0093]
It is preferable that the painted base treatment layer 24 further contain silica particles. By containing the silica particles, corrosion resistance can be further enhanced.
[0094]
Here, the content of the silica particles is preferably 0.5 parts by mass or higher and 100 parts by mass or less with respect to 100 parts by mass of the organic resin. When the content is less than 0.5 parts by mass, there may be cases where the effect of enhancing corrosion resistance cannot be obtained. When the content is higher than 100 parts by mass, there may be cases where the cohesion of the painted base treatment layer 24 is degraded and the adhesion of the organic coating particularly in the worked portion is degraded. The content of the silica particles is more preferably 5 to 50 parts by mass, and particularly preferably 10 to 30 parts by mass with respect to 100 parts by mass of the organic resin.
[0095]
The type of the silica particles is not particularly limited, and for example, silica particles such as colloidal silica or fiamed silica may be employed. As a commercial product, for example, SNOWTEX O, SNOWTEX N. SNOWTEX C, or SNOWTEXIPA-ST (manufactured by Nissan Chemical Industries Co.. Ltd.), ADELITE AT-20N or ADELITE AT-20A (manufactured by Asahi Denka Industries Co., Ltd.), Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.). functional spherical silica HPS series (manufactured by Toagosei Co., Ltd.). or Nipsil series (manufactured by Tosoh Silica Co.. Ltd.) may be employed.
41

^

[0096]
In addition, as the silica particles, spherical silica particles having an average particle size of 5 nm or greater and 20 nm or less are preferably contained in order to enhance corrosion resistance. When the average particle size of the spherical silica particles is smaller than 5 nm, there may be a problem such as gelation of the paint composition for forming the painted base treatment layer 24. When the average particle size thereof exceeds 20 nm, there may be cases where the effect of enhancing corrosion resistance caimot be sufficiently obtained.
[0097]
It is preferable that the painted base treatment layer 24 further contain a phosphoric acid compound in order to enhance corrosion resistance. It is more preferable that the phosphoric acid compound be a compound that releases phosphoric acid ions. In the case where the phosphoric acid compound is contained, when the paint composition comes into contact with the plating layer 23 used to form the painted base treatment layer 24 during the formation thereof, or when phosphoric acid ions derived from the phosphoric acid compound are eluted from the painted base treatment layer 24 after the formation of the painted base treatment layer 24, the phosphoric acid compound reacts with the Mg-based oxide film on the surface of the plating layer 23 and forms a poorly soluble phosphoric acid Mg-based film on the surface of the plating layer 23. Accordingly, the white rust resistance can be significantly enhanced. In a case where the phosphoric acid compound does not release phosphoric acid ions, that is, is insoluble in an environment, the insoluble phosphoric acid compound impedes the movement of corrosion factors such as water and oxygen, thereby enhancing corrosion resistance.
- 42

0
[0098]
The phosphoric acid compound is not particularly limited, and for example, phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, or tetraphosphoric acid or a salt thereof, phosphonic acids such as aminotri(methylenephosphonic acid), 1 -hydroxyethylidene-1, 1 -diphosphonic acid, ethylenediaminetetra(methylenephosphonic acid), or diethylenetriaminepenta(methylenephosphonic acid) or a salt thereof, or organic phosphoric acids such as phytic acid or a salt thereof may be employed. The type of cations of the salts is not particularly limited, and for example. Cu. Co, Fe, Mn, Sn, V, Mg, Ba, Al, Ca, Sr, Nb, Y, Ni or Zn may be employed. The phosphoric acid compounds (D) may be used sijigly or in a combination of two or more types thereof.
[0099]
The content of the phosphoric acid compound is preferably 0.5 to 40 parts by mass of the phosphoric acid compound with respect to the 100 parts by mass of the organic resin in the painted base treatment layer 24, and more preferably, 2 parts by mass to 15 parts by mass. When the content of the phosphoric acid compound is less than 0.5 parts by mass, there may be cases where the effect of enhancing corrosion resistance carmot be obtained. When the content exceeds 40 parts by mass, there may be cases where the corrosion resistance and the coating film adhesion of the worked portion are degraded and the paint stability used to form the coating film is degraded (more specifically, problems such as gelation and sedimentation of coagulation occur).
[0100]
It is preferable that the painted base treatment layer 24 further contain tannin, tannic acid, or tannate.

- 4

J -

[0101]
Tannin, tannic acid, or tannate is a generic term for aromatic compounds having complex structures with a number of phenolic hydroxyl groups that are widely distributed in the plant kingdom. Tannin, tannic acid, or tannate used for the painted base treatment layer 24 may be a hydrolyzable tannic acid or a condensed taimic acid. The tannin is not particularly limited, and for example, hamamelis tannin, persimmon tannin, tea tannin, gallnut taimin, gallic tannin, myrobalan tannin, divi divi tannin, algarovilla tannin, valonia tannin, or catechin tannin, may be employed. As the tannic acid or tannate, commercial products, for example, "Tannic acid extract A", "B tannic acid", "N tannic acid", "Industrial tannic acid", "Purified tannic acid", "Hi tannic acid", "F tannic acid", "Official tannic acid" (all manufactured b> Dainippon Pharmaceutical Co,, Ltd.), and "Tannic acid: AL" (manufactured by Fuji Chemical Industry Co., Ltd.) may be used. The tannins, the tannic acids, and the tannates may be used singly or in a combination or two or more types. [0102]
The tannin, tannic acid, or tannate strongly adheres to the plating layer 23, and adheres to a resin, particularly, an aqueous resin, thereby enhancing the adhesion between the painted base treatment layer 24 itself and the plated surface of the organic coating layer 25 at the upper layer thereof. Even in a case where the plated steel of the base is deformed, due to the adhesion, exfoliation of the painted base treatment layer 24 itself and the organic coating layer 25 at the upper layer thereof is prevented, and as a result, the corrosion resistance of the worked portion is also enhanced. The content of the tannin, tannic acid, or tannate is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the organic resin. When the content is less than 1 part by mass, an effect of addition is small. When the content exceeds 50 parts by mass,
44

there may be cases where the corrosion resistance of the worked portion is degraded or the stability of a base treatment solution is degraded. A more preferable content is 4 to 20 parts by mass with respect to 100 parts by mass of the organic resin.
[0103]
When a fluoride having etching ability is further added to the painted base treatment layer 24, the adhesion to the plated surface is further enhanced. As a result, there may be cases where the corrosion resistance of the worked portion is enhanced. Here, as the fluoride having etching ability, zinc fluoride tetrahydrate or zinc hexafluorosilicate hexahydrate may be used. The content of the fluoride having etching ability is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the organic resin. When the content is less than 0.5 parts by mass, the effect of addition is small. When the content exceeds 10 parts by mass, an effect of etching is saturated and thus the adhesion is not improved, which is uneconomical.
[0104]
The adhesion amount of the painted base treatment layer 24 is not particularly limited, and is preferably 10 to 2000 mg/m , more preferably 20 to 1000 mg/m , even more preferably 20 to 300 mg/m , and particularly preferably 40 to 120 mg/m . When the adhesion amount of the painted base treatment layer 24 is less than 10 mg/m , sufficient corrosion resistance and coating film adhesion cannot be obtained. In contrast, when the adhesion amount of the painted base treatment layer 24 exceeds
•y
2000 mg/m , not only is it economically disadvantageous, but also coating film defects such as blisters and unevenness in the adhesion amount occur in a case where the painted base treatment layer 24 is foiTned from a water-based paint. Therefore, the
45

appearance or performance of the painted plated-steel as an industrial product cannot be stably obtained. In addition, the cohesion of the painted base treatment layer 24 is insufficient and results in brittleness, and thus there may be cases where adhesion and corrosion resistance are degraded. [0105]
The adhesion amount of the painted base treatment layer 24 may be obtained by a method appropriately selected from existing methods such as calculating a mass difference in the plated steel before and after painting, calculating a mass difference in the plated steel before and after the painted base treatment layer 24 is exfoliated after painting, and performing fluorescent X-ray analysis on the coating film and measuring the amount of present elements of which the contents in the film are known in advance.
[0106] [Organic coating layer 25]
The painted plated-steel according to each embodiment of the present invention is made by coating one surface or both surfaces of the plated steel with one or more layers of organic coating layers 25 via the painted base treatment layer 24. Otherwise, in a site for which high corrosion resistance or organic coating adhesion is not mentioned, the painted base treatment layer 24 and the organic coating layer 25 may be partially omitted. [0107]
As a binder resin which is the main component of the coating film of the organic coating layer 25, a polyester resin, an epoxy resin, a urethane resin, an acrylic resin, a melamine resin, or a fluororesin is exemplified, and although not particularly limited, a thermosetting resin is more preferable in a case where the painted hot-dip plated steel is used for the purpose of being worked. As the thermosetting resin, a
46 -

polyester-based resin such as an epoxy polyester resin, a polyester resin, a melamine polyester resin, or a urethane polyester resin or an acrylic resin may be employed, and these resins have better workability than other resins and are less likely to have cracks being generated in the coating film layer even after severe work. [0108]
The polyester-based resin as the main component of the organic coating layer 25 is not particularly limited, and a generally well-known ester compound of a polybasic acid and a polyhydric alcohol, which is synthesized by a generally well-known esterification reaction, may be used. [0109]
The polybasic acid is not particularly limited, and for example, phthalic acid, isophthalic acid, terephthalic acid, phthalic anhydride, trimellitic anhydride, maleic acid, adipic acid, or fiimaric acid may be employed. The polybasic acids may be used singly or in a combination of a plurality of types thereof [0110]
The polyhydric alcohol is not particularly limited, and for example, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, neopentylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, polytetramethylene ether glycol, glycerin, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol. pentaerythritol, or dipentaerythritol may be employed. The polyhydric alcohols may be used singly or by mixing two or more types thereof [0111]
When the polyester-based resin is used, when a curing agent is blended, the hardness of the coating film layer is increased, and thus scratch resistance is enhanced,
47

which is preferable. The curing agent is not particularly limited, and any one or both of a generally well-knovm amino resin and a polyisocyanate compound may be used. [0112]
The amino resin is not particularly limited, and for example, a resin obtained by a reaction between urea, benzoguanamine, or melamine and fomialdehyde, or a resin obtained by alkyl-etherifying the resin using alcohol may be used. Specifically, methylated urea resin, n-butylated benzoguanamine resin, methylated melamine resin, n-butylated melamine resin, or iso-butylated melamine resin may be employed. [0113]
A resin that is widely used in the painted hot-dip plated steel field is a polyester/melamine-based resin which contains a polyester-based resin as the main resin and a melamine-based resin as a curing agent. In addition, the melamine-based resin mentioned here represents at least one type of methylated melamine resin, n-butylated melamine resin, and iso-butylated melamine resin. [0114]
The polyisocyanate compound is not particularly limited, and for example, an isocyanate compound blocked by a blocking agent such as phenol, cresol, aromatic secondary amine, tertiary alcohol, lactam, or oxime is preferable. As a more preferable polyisocyanate compound, HDI (hexamethylene diisocyanate) or a derivative thereof, TDI (tolylene diisocyanate) or a derivative thereof. MDI (diphenylmethane diisocyanate) or a derivative thereof, XDI (xylylene diisocyanate) or a derivative thereof, IPDI (isophorone diisocyanate) or a derivative thereof, TMDI (trimethyl hexamethylene diisocyanate) or a derivative thereof, hydrogenated TDI or a derivative thereof, hydrogenated MDI or a derivative thereof, or hydrogenated XDI or a derivative thereof may be employed.
48 -

4

[0115]
In the present invention, the coating film configuration of the organic coating layer 25 is not particularly limited, and a configuration in which only a single layer of coating film is included, two or more layers of coating films are included, or a single layer of coating film and two or more layers of coating films are partially present while being mixed may be employed. However, as described below, in order to ensure excellent design and corrosion resistance, the coating film layer is preferably made of two or more layers of coating films.
[0116]
In a case where the organic coating layer 25 includes a plurality of layers including two or more layers, it is preferable that at least one layer be a layer containing a corrosion-resistant pigment in order to enhance the corrosion resistance of the painted hot-dip plated steel. It is more preferable that the layer containing the corrosion-resistant pigment be disposed closer to the plated steel side than the other layers in order to enhance the corrosion resistance. The corrosion-resistant pigment is not particularly limited, and for example, a generally well-known chromate-free corrosion-resistant pigment including a phosphoric acid-based corrosion-resistant pigment such as zinc phosphate, iron phosphate, aluminium phosphate, zinc phosphite, or aluminium tripolyphosphate, a molybdic acid-based corrosion-resistant pigment such as calcium molybdate, aluminium molybdate, or barium molybdate, a vanadium-based corrosion-resistant pigment such as vanadium oxide, a silicate-based corrosion-resistant pigment such as calcium silicate, a silica-based corrosion-resistant pigment such as water-dispersible silica, fumed silica, or calcium ion-exchanged silica, and a ferroalloy-based corrosion-resistant pigment such as ferrosilicon. or a generally well-
49

known chromium-based corrosion-resistant pigment such as strontium cliromate, potassium chromate, barium chromate, or calcium chromate may be used. However, from the viewpoint of environmental conservation in recent years, as the corrosion-resistant pigment in the present invention, the chromate-free corrosion-resistant pigment is more preferably used. The corrosion-resistant pigments may be used singly or in a combination of a plurality of types thereof
[0117]
The addition amount of the corrosion-resistant pigment is preferably 1 mass% or higher and 40 mass% or less in terms of solid content of the layer containing the corrosion-resistant pigment in the organic coating layer 25. When the addition amount of the corrosion-resistant pigment is less than 1 mass%. an improvement in the corrosion resistance is not sufficient. When the addition amount exceeds 40 mass%, workability is degraded, and there may be cases where the coating layer peels off during work, resulting in a tendency to decrease the corrosion resistance.
[0118]
In addition, in the case where the organic coating layer 25 includes the plurality of layers including two or more layers, it is preferable that at least one layer thereof be a colored plating layer containing a coloring pigment in order to enhance the design of the painted plated-steel. The outermost surface layer thereof may be the colored coating layer containing the coloring pigment, or the outermost surface layer may be a coating having high permeability and the colored coating layer may be disposed at the lower layer thereof
[0119]
The coloring pigment is not particularly limited, and for example, a well-known pigment such as titanium oxide, zinc oxide, iron oxide, zirconium oxide.
50

calcium carbonate, barium sulfate, carbon black, phthalocyanine blue, naphthol red, disazo yellow, or disazo pyrazolone orange may be used. An inorganic pigment or an organic pigment may also be employed. In addition, as the coloring pigment, a generally well-known metallic pigment such as aluminium pigment or nickel pigment may be used, and a pigment having any form such as a granular or tlake form may be used. The coloring pigments may be used singly or in a combination of a plurality of types thereof.
[0120]
The addition amount of the coloring pigment is preferably 5 iTiass% or higher and 70 mass% or less in terms of solid content of the layer containing the coloring pigment in the organic coating layer 25. When the addition amount of the coloring pigment is less than 5 mass%, there may be cases where intended design (coloring effect) is degraded. When the addhion amount exceeds 70 mass%, there may be cases where the corrosion resistance or work resistance of the coating layer is deteriorated.
[0121]
The thickness of the organic coating layer 25 is preferably 0.2 to 100 [.im. When the thickness is smaller than 0.2 |am, the effects of the organic coating layer 25 pertaining to coloring, design application, blocking of corrosion factors for preventing corrosion of the plated steel sheet, and the like are insufficient. When the thickness exceeds 100 |.im, since the effect of the coating layer is saturated, it is economically disadvantageous, and there may be problems in that the surface of the coating layer is likely to become uneven and is less likely to obtain a uniform appearance and cracking is likely to occur in the organic coating at the worked portion of the painted plated-steel sheet. The thickness of the organic coating layer 25 is preferably 3 to 40 |.im,
- 51

and more preferably 15 to 40 |j,m.
[0122]
The thickness of the organic coating layer 25 may be measured by observing the cross-section of the organic coating layer 25 or using an electromagnetic film thickness meter or the like. Otherwise, the thickness may also be calculated by dividing the mass of the organic coating layer 25 that adheres to the unit area of the plated steel by the specific gravity of the organic coating layer 25 or the specific gravity after drying an application solution. The mass of the adhered o'-ganic coating layer 25 may be obtained by a method appropriately selected from existing methods such as calculating a mass difference in the plated steel before and after painting, calculating a mass difference in the plated steel before and after the organic coating layer 25 is exfoliated after painting, and performing fluorescent X-ray analysis on the coating film and measuring the amount of present elements of which the contents in the film are known in advance. The specific gravity of the organic coating layer 25 or the specific gravity after drying the paint may be obtained by a method appropriately selected from existing methods such as measuring the volume and mass of the isolated organic coating layer 25, measuring the volume and mass after putting an appropriate amount of paint in a container and drying the paint, and calculation from the blending amounts of the constituent components of the organic coating layer 25 and the known specific gravity of each component.
[0123] [Pretreatment Layer 28]
By further providing a pretreatment layer 28 at the lower layer of the painted base treatment layer 24, that is, between the painted base treatment laver 24 and the metal sheet, the adhesion between the painted base treatment Ia\er 24 and the plated
52

^

steel as the base material can be further enhanced and the corrosion resistance of the painted plated-steel can be further enhanced. The composition of the pretreatment layer 28 is not particularly limited, and a silane coupling agent, a crosslinkable zirconium compound, a crosslinkable titanium compound, or the like is preferably used. They may be used singly or in a combination of two or more types thereof.
[0124]
The type of the silane coupling agent is not particularly limited, and for example, vinyltrimethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, y-aminopropyltrimethoxysilane, y-aminopropylethoxysilane, N-[2-(vinylbenzylamino)ethyl] -3 -aminopropyltrimethoxysialne, y-
methacryloxypropylmethyldimethoxysilane, y-methacryloxypropyltrimethoxysilane, y-methacryloxypropylmethyldiethoxysilane, y-methacryloxypropyltriethoxysilane, y-glycidoxypropyltriethoxysilane, y-glycidoxypropylmethyldiethoxysilane, y-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-P-(aminoethyl)-y-aminopropyltrimethoxysilane, N-(3-(aminoethyl)-Y-aminopropyltriethoxysilane, N-P-(aminoethyl)-y-aminopropylmethyldimethoxysilane, N-phenyl-y-aminopropyltrimethoxysilane, and y-mercaptopropyltrimethoxysilane sold by Shin-Etsu Chemical Co., Ltd., Dow Coming Toray Co.,Ltd. Chisso Corporation, Momentive Performance Materials Japan Inc., and the like may be employed. The silane coupling agents may be used singly or in a combination of two or more types thereof.
[0125]
The crosslinkable zirconium compound is not particularly limited, and for example, zirconium nitrate, zirconium acetate, zirconium sulfate, ammonium zirconium carbonate, potassium zirconium carbonate, sodium zirconium carbonate.
53

zirconium acetate, or the like may be employed. Among these compounds, a zirconium compound containing zirconium carbonate complex ions is preferable. The zirconium compound containing zirconium carbonate complex ions is not particularly limited, and an ammonium salts, a potassium salt, or a sodium salt of zirconium carbonate complex ions [Zr(C03)2(OH)2] ' or [Zr(C03)3(OH)] ' may be employed. The crosslinkable zirconium compounds may be used singly or in a combination of two or more types thereof
[0126]
The crosslinkable titanium compound is not particularly limited, and for example, dipropoxybis(triethanolaminato)titanium,
dipropoxybis(diethanolaminato)titanium, propoxytris(diethanolaminato)titanium, dibutoxybis(triethanolaminato)titanium, dibutoxybis(diethanolaminato)titanium, dipropoxybis(acetylacetonato)titanium, dibutoxybis(acetylacetonato)titanium, dihydroxybis(lactato)titanium monoammonium salt, dihydroxybis(lactato)titanium diammonium salt, propanedioxytitanium bis(ethyl acetoacetate). oxotitanium bis(monoammonium oxalate), or isopropyl tri(N-amidoethylaminoethyl)titanate may be employed. The crosslinkable titanium compounds may be used singly or in a combination of two or more types thereof
[0127] [Method of Producing Painted Plated-Steel]
The painted plated-steel according to this embodiment is produced by performing aluminium-zinc alloy plating on the surface of the steel 1 and forming the painted base treatment layer 24 and the organic coating layer 25 on the upper surface thereof
[0128]
54 -

♦

[Method of Producing Hot-dip Plated Steel]
In the exemplary embodiment, during production of the hot-dip plated steel, the hot-dip plating bath 2 which has the same composition as the composition of the constituent elements of the plating layer 23 is prepared. Although the alloy layer 26 is formed between the steel 1 and the plating layer 23 by the hot-dip plating treatment, a change in the composition due to the formation is small and negligible.
[0129]
In the embodiment, the hot-dip plating bath 2 contains, for example, 25 mass% to 75 mass% of Al, 0.5 mass% to 10 mass% of Mg, 0.02 mass% to 1.0 mass% of Cr, 0.5 mass% to 10 mass% of Si with respect to Al, 1 mass ppm to 1000 mass ppm of Sr, 0.1 mass% to 1.0 mass% of Fe, and a balance consisting of Zn. Zn constitutes a balance obtained by excluding constitutional elements other than Zn from all the constitutional elements of the hot-dip plating bath 2. A mass ratio Si:Mg in the hot-dip plating bath 2 is preferably in a range from 100:50 to 100:300.
[0130]
The hot-dip plating bath 2 may further contain an element selected from the group consisting of alkaline earth elements, Sc, Y, lanthanoid elements, Ti, and B. These elements are optionally contained in the hot-dip plating bath 2. The total content of alkaline earth elements (Be, Ca, Ba, Ra), Sc, Y, and lanthanoid elements (for example. La, Ce, Pr, Nd, Pm, Sm, and Eu) in the hot-dip plating bath 2 is preferably less than or equal to 1.0% by mass ratio. When the hot-dip plating bath 2 contains at least one element of Ti and B, the total content of Ti and B in the hot-dip plating bath 2 is preferably in a range from 0.0005% to 0.1% by mass ratio.
[0131]
It is preferable that the hot-dip plating bath 2 do not ciintain elements other
- 55

than the above-described elements. It is particularly preferable that the hot-dip plating bath 2 contain only Al, Zn, Si, Mg, Cr, Sr, and Fe. It is also preferable that the hot-dip plating bath 2 contain only Al, Zn, Si, Mg, Cr, Sr, Fe, and an element selected from the group consisting of alkaline earth elements, Sc, Y, lanthanoid elements, Ti, andB.
[0132]
For example, when the hot-dip plating bath 2 is prepared, it is preferable that the hot-dip plating bath 2 contain, by mass ratio, 25% to 75% of Al. 0.02% to 1.0% of Cr, 0.5% to 10% of Si with respect to Al, 0.1 % to 0.5% of Mg. 0.1 % to 0.6% of Fe, and 1 ppm to 500 ppm of Sr, optionally further contain an element selected from the group consisting of alkaline earth elements, lanthanoid elements. Ti. and B, and contain a balance consisting of Zn.
[0133]
In this case, it is needless to say that the hot-dip plating bath 2 may contain unavoidable impurities such as Pb, Cd, Cu, and Mn. It is preferable that the content of the unavoidable impurities be small. It is particularly preferable that the total content of the unavoidable impurities be less than or equal to 1 mass% by mass ratio with respect to the hot-dip plating bath 2.
[0134]
When the steel 1 is subjected to the hot-dip plating treatment using the hot-dip plating bath 2 having such a coinposition, the corrosion resistance particularly on the surface of the plating layer 23 is particularly improved by Al. edge creep particularly on a cut end surface of the hot-dip plated steel is suppressed by the sacrificial corrosion preventing action of Zn, and thus high corrosion resistance is imparted to the hot-dip plated steel.
56

[0135]
Furthermore, the plating layer 23 contains Mg which is less noble than Zn such that the sacrificial corrosion preventing action of the plating layer 23 is further strengthened, and the corrosion resistance of the hot-dip plated steel is further improved.
[0136]
Further, the wrinkling is difficult to occur on the plating layer 23 which is formed by the hot-dip plating treatment. In the related art, when a molten metal (hot-dip plating metal) containing Mg is attached onto the steel 1 by the hot-dip plating treatment, Mg is likely to be concentrated on the surface of the hot-dip plating metal. Therefore, a Mg-based oxide film is formed, and the wrinkling of the plating layer 23 is likely to occur due to this Mg-based oxide film. However, when the plating layer 23 is formed by using the hot-dip plating bath 2 having the above-described composition, the concentration of Mg on the surface of the hot-dip plating metal attached onto the steel 1 is suppressed. As a result, even when the hot-dip plating metal flows, wrinkling is difficult to occur on the surface of the plating layer 23. Further, the fluidity of the inside of the hot-dip plating metal is suppressed, and the flow of the hot-dip plating metal is suppressed. Therefore, the wrinkling is further suppressed.
[0137]
It is considered that the concentration of Mg and the fluidity of the hot-dip plating metal are suppressed by the following mechanism.
[0138]
In a process of cooling the hot-dip plating metal, which is attached onto the surface of the steel 1, to be solidified, the a-Al phase is precipitated as a primary phase
57

and is dendritically grown. When the solidification of the Al-rich a-Al phase progresses, the concentrations of Mg and Si in the remaining hot-dip plated metal (that is, in unsolidified components of the hot-dip plated metal) are gradually increased. Next, when the steel 1 is cooled and a temperature thereof is further decreased, a Si-containing phase (Si-Mg phase) in the remaining hot-dip plating metal is solidified and precipitated. As described above, this Si-Mg phase is a phase composed of an alloy of Mg and Si. The precipitation and growth of the Si-Mg phase is promoted by Cr, Fe, and Sr. By incorporating Mg in the hot-dip plating metal into the Si-Mg phase, the transfer of Mg to the surface of the hot-dip plating metal is inhibited, and the concentration of Mg on the surface of the hot-dip plating metal is suppressed. [0139]
Further, Sr in the hot-dip plating metal also contributes to the suppressing of concentration of Mg. The reason is considered to be as follows. Since Sr in the hot-dip plating metal is an element which is likely to be oxidized similarly to Mg, Sr and Mg competitively form oxide films on the plating surface. As a result, the formation of a Mg-oxide film is suppressed. [0140]
Further, by the Si-Mg phase being solidified and grown in the remaining hot-dip plating metal other than the a-Al phase which is the primary phase as described above, the hot-dip plating metal is in the solid-liquid mixed phase. Therefore, the fluidity of the hot-dip plated metal is decreased, and the wrinkling of the plating layer surface is suppressed. [0141]
Fe is important from the viewpoint of controlling the microstructure and spangle structure of the plating layer 23. The reason vi^hy Fe has an effect on the
- 58 -

structure of the plating layer 23 is not clear at this moment, but is considered to be that Fe forms an alloy with Si in the hot-dip plating metal, and this alloy functions as a solidification nucleus during the solidification of the hot-dip plating metal.
[0142]
Further, since Sr is a ignoble element similarly to Mg, the sacrificial corrosion preventing action of the plating layer 23 is further strengthened by Sr, and the corrosion resistance of the hot-dip plated steel is further improved. Sr exhibits an action of suppressing the acicularization of the precipitation fonn of the Si phase and the Si-Mg phase. As a result, the Si phase and the Si-Mg phase are spheroidized, and the cracking of the plating layer 23 is suppressed.
[0143]
During the hot-dip plating treatment, the alloy layer 26 containing a part of Al in the hot-dip plating metal is formed between the plating layer 23 and the steel 1. For example, when the steel 1 is not subjected to pre-plating as described below, the Fe-Al-based alloy layer 26 containing Al in the hot-dip plating bath 2 and Fe in the steel 1 as major components is formed. When the steel 1 is subjected to pre-plating as described below, the alloy layer 26, which contains Al in the hot-dip plating bath 2 and a part or all of constitutional elements of the pre-plating and optionally further contains Fe in the steel 1, is formed.
[0144]
When the hot-dip plating bath 2 contains Cr, the alloy layer 26 further contains Cr along with Al as a constitutional element. Depending on the composition of the hot-dip plating bath 2, whether or not being subjected to pre-plating, and the composition of the steel 1, in addition to Al and Cr, the alloy layer 26 may contain various metal elements such as Si, Mn. Fe, Co. Ni. Cu, Zn. and Sn as constitutional
59

elements.
[0145]
The alloy layer 26 contains Cr such that a concentration of a part of Cr in the hot-dip plating metal is higher than that in the plating layer 23. When such as an alloy layer 26 is formed, the growth of the Si-Mg phase in the plating layer 23 is promoted by Cr in the alloy layer 26, the volume ratio of the Si-Mg phase in the plating layer 23 is increased, and the ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 is increased. As a result, the wrinkling of the plating layer 23 is further suppressed. Further, by the alloy layer 26 be'ng formed, the corrosion resistance of the hot-dip plated steel is further improved. That is, the growth of the Si-Mg phase near the alloy layer 26 in the plating layer 23 is promoted, which decreases the area ratio of the Si-Mg phase on the surface of the plating layer 23. As a result, the nmning of the plating layer 23 is suppressed, and the corrosion resistance of the plating layer 23 is maintained over a longer period of time. In particular, the ratio of the Cr content in the alloy layer 26 to the Cr content in the plating layer 23 is preferably 2 to 50. The ratio of the Cr content in the alloy layer 26 to the Cr content in the plating layer 23 is more preferably 3 to 40 and still more preferably 4 to 25. The Cr content in the alloy layer 26 can be obtained by measuring a cross-section of the plating layer 23 using an energy dispersive X-ray analyzer (EDS). [0146]
When the thickness of the alloy layer 26 is excessive, the workability of the hot-dip plated steel deteriorates, but the excessive growth of the alloy layer 26 is suppressed by the action of Si in the hot-dip plating bath 2. Therefore, superior workability of the hot-dip plated steel is secured. The thickness of the alloy layer 26 is preferably in a range from 0.05 ).im to 5 |.im. When the thickness of the alloy layer
60

«

26 is in the above-described range, the corrosion resistance of the hot-dip plated steel is sufficiently improved, and the workability thereof is also improved.
[0147]
Further, in the plating layer 23, the concentration of Cr near the surface thereof is maintained in a predetermined range. Accordingly, the corrosion resistance of the plating layer 23 is further unproved. The reason is not clear but is considered to be that, by Cr being bonded with oxygen, a complex oxide film is formed near the surface of the plating layer 23. In order to improve the corrosion resistance of the plating layer 23, it is preferable that a Cr content in the outermost layer which is located at a depth of 50 nm from the surface of the plating layer be 100 mass ppm to 500 mass ppm.
[0148]
When the hot-dip plating bath 2 contains Cr, the corrosion resistance of the plating layer 23 after bending and deformation is also improved. The reason is considered to be as follows. When the plating layer 23 is subjected to a strict bending deformation, cracks may be initiated on the plating layer 23 and the coating film on the plating layer 23. At this time, water and oxygen are infiltrated into the plating layer 23 through the cracks, and an alloy in the plating layer 23 is directly exposed to corrosive factors. However, Cr which is present particularly in the surface of the plating layer 23 and Cr which is present in the alloy layer 26 suppress the corrosion reaction of the plating layer 23, thereby suppressing the expansion of corrosion originating from the cracks.
[0149]
The hot-dip plating metal which is used in the prefeiTcd embodiment is a multi-element hot-dip plating metal containing seven or more elements, and a
61

fm

solidification process thereof is extremely complex is theoretically difficult to predict. However, the present inventors have found the above-described important facts through observation and the like in experiments.
[0150]
By controlling the composition of the hot-dip plating bath 2 as described above, the wrinkling and running of the plating layer 23 are suppressed, and the corrosion resistance and workability of the hot-dip plated steel are secured, as described above.
[0151]
When an Al content in the hot-dip plating bath 2 is less than 25%, the Zn content in the plating layer 23 is excessive, and the corrosion resistance on the surface of the plating layer 23 is insufficient. When this content is greater than 75%, the sacrificial corrosion preventing effect of Zn is decreased, the plating layer 23 is hardened, and the bendability of the hot-dip plated steel is decreased. Further, when this content is greater than 75%, the fluidity of the hot-dip plating metal is increased, which may cause the wrinkling of the plating layer 23. The Al content is particularly preferably greater than or equal to 45%. In addition, the Al content is particularly preferably less than or equal to 65%. The Al content is particularly preferably in a range from 45% to 65%).
[0152]
When a Cr content in the hot-dip plating bath 2 is less than 0.02%), it is difficult to sufficiently secure the corrosion resistance of the plating layer 23 and to sufficiently suppress the wrinkling and running of the plating layer 23. When this content is greater than 1.0%), the effect of improving corrosion resistance is saturated, and dross is likely to be fonned in a hot-dip plating bath 2. The Cr content is
62 -

#

particularly preferably greater than or equal to 0.05%. In addition, the Cr content is particularly preferably less than or equal to 0.5%. The Cr content is further preferably in a range from 0.07%) to 0.2%).
[0153]
When an Si content in the hot-dip plating bath 2 is less than 0.5% with respect to Al, the above-described effects are not exhibited. When this content is greater than 10%, the effect of Si is saturated, and dross is likely to be formed in the hot-dip plating bath 2. The Si content is particularly preferably greater than or equal to 1.0%. In addition, the Si content is particularly preferably less than or equal to 5.0%. The Si content is further preferably in a range from 1.0%o to 5.0%.
[0154]
When a Mg content in the hot-dip plating bath 2 is less than 0.1%, the corrosion resistance of the plating layer 23 is not sufficiently secured. When this content is greater than 10%, the effect of improving coiTosion resistance is saturated, and dross is likely to be formed in the hot-dip plating bath 2. The Mg content is more preferably greater than or equal to 0.5%) and still more preferably greater than or equal to 1.0%). In addition, the Mg content is more preferably less than or equal to 5.0% and still more preferably less than or equal to 3.0%. The Mg content is particularly preferably in a range from 1.0% to 3.0%.
[0155]
When a Fe content in the hot-dip plating bath 2 is less than 0.1 %, the microstructure and spangle structure of the plating layer 23 are coarsened, which deteriorates the appearance and workability of the plating layer 23. When the Fe content is greater than 0.6%, the spangle structure of the plating layer 23 is excessively refined or disappears. As a result, the appearance is not impro\ ed h\ the spangle
63

structure, and dross is likely to be formed in the hot-dip plating bath 2. The Fe content is particularly preferably greater than or equal to 0.2%. In addition, the Fe content is particularly preferably less than or equal to 0.5%. The Fe content is particularly preferably in a range from 0.2%) to 0.5%o.
[0156]
When an Sr content in the hot-dip plating bath 2 is less than 1 ppm, the above-described effects are not exhibited. When this content is greater than 500 ppm, the effect of Sr is saturated, and dross is likely to be formed in the hot-dip plating bath 2. The Sr content is particularly preferably greater than or equal to 5 ppm. In addition, the Sr content is more preferably less than or equal to 300 ppm. The Sr content is still more preferably in a range from 20 ppm to 50 ppm.
[0157]
When the hot-dip plating bath 2 contains an element selected from the group consisting of alkali earth elements and lanthanoid elements, alkaline earth elements (Be, Ca, Ba, Ra), Sc, Y, and lanthanoid elements (for example. La. Ce, Pr, Nd, Pm, Sm, and Eu) have the same effects as those of Sr. As described above, the total content of these elements in the hot-dip plating bath 2 is preferably less than or equal to 1.0 mass%) by mass ratio.
[0158]
Particularly when the hot-dip plating bath 2 contains Ca. dross is significantly suppressed in the hot-dip plating bath 2. In a case where the hot-dip plating bath 2 contains Mg, even when a Mg content is less than or equal to 10 mass%, dross is unavoidably formed to some degree. Therefore, in order to secure a superior appearance of the hot-dip plated steel, it is necessary to remove dross from the hot-dip plating bath 2. However, when the hot-dip plating bath 2 further contains Ca, dross
- 64

formed by Mg is significantly suppressed. As a result, deterioration in the appearance of the hot-dip plated steel by dross is further suppressed, and the time and effort required for removing dross from the hot-dip plating bath 2 are decreased. A Ca content in the hot-dip plating bath 2 is preferably in a range from 100 mass ppm to 5000 mass ppm. When this content is greater than 100 mass ppm, dross is efficiently suppressed in the hot-dip plating bath 2. When a Ca content is excessive, dross may be formed by Ca. By controlling the Ca content to be less than or equal to 5000 mass ppm, dross formed by Ca is suppressed. When the Ca content is more preferably in a range from 200 mass ppm to 1000 mass ppm.
[0159]
When the hot-dip plating bath 2 contains at least one of Ti and B, the a-Al phase (dendritic structure) of the plating layer 23 is refined, and the spangle structure of the plating layer 23 is refined. As a result, the appearance of the plating layer 23 is improved by the spangle structure. Further, the wrinkling of the plating layer 23 is further suppressed. The reason is considered to be that the Si-Mg phase is also refined by the action of Ti and B, this refined Si-Mg phase solidifies a hot-dip plating metal, and the flow of the hot-dip plating metal is effectively suppressed in a process of forming the plating layer 23. Further, due to the refinement of the plating structure, the concentration of stress in the plating layer 23 during bending is relaxed, the initiation of large cracks is suppressed, and bendability is further improved. In order to exhibit the above-described effects, the total content of Ti and B in the hot-dip plating bath 2 is preferably in a range of 0.0005 mass% to 0.1 mass% by mass ratio. The total content of Ti and B is particularly preferably greater than or equal to 0.001%. The total content of Ti and B is particularly preferably less than or equal to 0.05%. The total ratio of Ti and B is particularly preferably in a range from 0.001% to 0.05%.
- 65 -

[0160]
The plating layer 23 is formed by the hot-dip plating treatment using such a hot-dip plating bath 2. In the plating layer 23, the concentration of Mg on the surface is suppressed as described above. Accordingly, as described above, it is preferable that a Mg content in any region having a diameter of 4 mm and a depth of 50 nm inside an outermost layer, which is located at a depth of 50 nm from the surface of the plating layer 23, be less than 60 mass%. In this case, the amount of a Mg-based oxide film is particularly small in the outermost layer of the plating layer 23, and the wrinkling caused by the Mg-based oxide film is further suppressed. As the Mg content in the outermost layer is decreased, the wrinkling caused by the Mg-based oxide film is suppressed. The Mg content is more preferably less than 40 mass%. still more preferably less than 20 mass%, and yet still more preferably less than 10 mass%. Particularly in the outermost layer of the plating layer 23 having a thickness of 50 nm, it is preferable that a portion having a Mg content of 60 mass% or greater is not present, it is more preferable that a portion having a Mg content of 40 mass% or greater is not present, and it is still preferable that a portion having a Mg content of 20 mass% or greater is not present. [0161]
The physical meaning of the Mg content will be described. The Mg content in a MgO oxide having a stoichiometric composition is approximately 60 mass%. That is, the Mg content being less than 60 mass% represents that MgO (oxide film of MgO alone) having a stoichiometric composition is not present in the outermost layer of the plating layer 23 or that the formation of MgO having a stoichiometric composition is significantly suppressed. In the embodiment, the excessive oxidation of Mg in the outermost layer of the plating layer 23 is suppressed, and thus the
66

formation of an oxide film MgO alone is suppressed. On the outemiost layer of the plating layer 23, a composite oxide containing small or large amounts of oxides of elements other than Mg such as Al, Zn, and Sr is formed. Therefore, it is considered that the Mg content in the surface of the plating layer 23 is relatively decreased.
[0162]
The Mg content in the outermost layer of the plating layer 23 can be analyzed using a glow discharge spectrometer. When it is difficult to obtain an accurate value for quantitative analysis of concentration, the absence of an oxide film of MgO alone in the outermost layer of the plating layer 23 can be confirmed by comparing concentration curves of the respective plural elements contained in the plating layer 23.
[0163]
It is preferable that the volume ratio of the Si-Mg phase in the plating layer 23 be 0.2 vol% to 15 vol%. The volume ratio of the Si-Mg phase is more preferably 0.2% to 10%, still more preferably 0.3% to 8%, and yet still more preferably 0.4% to 5%. When the Si-Mg phase is present in the plating layer 23 as described above, Mg is sufficiently incorporated into the Si-Mg phase during the formation of the plating layer, and the flow of the hot-dip plating metal is sufficiently inhibited by the Si-Mg phase. As a result, the wrinkling of the plating layer 23 is further suppressed.
[0164]
In the hot-dip plated steel, the wrinkling of the surface of the plating layer 23 is suppressed as described above. As a result, protrusions having a height of greater than 200 fj,m and a steepness of greater than 1.0 are not present particularly on the surface of the plating layer 23, which is preferable. The steepness refers to a value defined by (protrusion height (|im))-^(protrusion bottom width (|.im)). The bottom of a protrusion refers to a portion where the protrusion intersects \\ ith a virtual plane
67

^

containing a flat surface around the protrusion. The height of a protrusion refers to the height from the bottom of the protrusion to the top of the protrusion. When the steepness is low, the appearance of the plating layer 23 is further improved. Further, when the painted base treatment layer 24 is formed on the plating layer 23 as described below, the protrusions are prevented from penetrating the painted base treatment layer 24, and the thickness of the painted base treatment layer 24 can be easily made uniform. Accordingly, the appearance of the painted hot-dip plated steel is enhanced, and the painted hot-dip plated steel can exhibit more excellent corrosion resistance and the like by the painted base treatment layer 24.
[0165]
The concentration degree of Mg, the state of the Si-Mg phase, the thickness of the alloy layer 26, and the steepness of protrusions on the surface of the plating layer 23 can be controlled by performing the hot-dip plating treatment on the steel 1 using the hot-dip plating bath 2 having the above-described composition.
[0166]
During the hot-dip plating treatment, the hot-dip plating treatment used to form the plating layer may be performed on the steel 1 in which a pre-plating layer 27 containing at least one element selected from the group consisting of Cr. Mn, Fe, Co, Ni, Cu, Zn, and Sn is formed. By performing a pre-plating treatment on the steel 1 before performing the hot-dip plating treatment, the pre-plating layer 27 is formed on the surface of the steel 1. Due to the pre-plating layer 27, the vvettabiiity between the steel 1 and the hot-dip plating metal during the hot-dip plating treatment is improved, and the adhesion between the steel 1 and the plating layer 23 is improved.
[0167]
Although depending on the kind of a metal constituting the pre-plating layer
68

^^^

27, the pre-plating layer 27 contributes to further improvement in the appearance and corrosion resistance of the surface of the plating layer 23. For example, when the pre-plating layer 27 containing Cr is formed, the formation of the alloy layer 26 containing Cr between the steel 1 and the plating layer 23 is promoted, and the corrosion resistance of the hot-dip plated steel is further improved. For example, when the pre-plating layer 27 containing Fe or Ni is formed, the wettability between the steel 1 and the hot-dip plated metal is improved, the adhesion of the plating layer 23 is greatly improved, the precipitation of the Si-Mg phase is promoted, and the surface appearance of the plating layer 23 is further improved. It is considered that the precipitation of the Si-Mg phase is promoted by a reaction between the pre-plating layer 27 and the hot-dip plating metal.
[0168]
An attached amount of the pre-plating layer 27 is not particularly limited, but an attached amount on a single surface of the steel 1 is preferably in a range from 0.1
7 9 "1
g/m to 3 g/m". When the attached amount is less than 0.1 g/m". it is difficult to coat the surface of the steel with the pre-plating layer 27, and the improvement effects obtained by pre-plating are not sufficiently exhibited. In addition, when the attached amount is greater than 3 g/m , the improvement effects are saturated, and the production cost is high.
[0169]
Hereinafter, the summary of a hot-dip plating apparatus used to perform the hot-dip plating treatment on the steel 1; and preferable conditions of the hot-dip plating treatment will be described.
[0170]
The steel 1 which is a treatment target is a member formed from steel such as
69

^^s

carbon steel, alloy steel, stainless steel, nickel-chromium steel, nickel-chromium-molybdenum steel, chromium steel, chromium-molybdenum steel, and manganese steel. Examples of the steel 1 include various members such as a steel sheet, a steel plate, a die steel, a steel tube, and a steel wire. That is, the shape of the steel 1 is not particularly limited.
[0171]
The steel 1 may be subjected to a flux treatment before the hot-dip plating treatment. Due to this flux treatment, the wettability and adhesion of the steel 1 vdth the hot-dip plating bath 2 can be improved. The steel 1 may be subjected to a thermal annealing and reduction treatment before being dipped in the hot-dip plating bath 2, and this treatment may not be performed. As described above, the steel 1 may be subjected to the pre-plating treatment before the hot-dip plating treatment.
[0172]
In the foUowdng description, a process of producing a hot-dip plated steel (hot-dip plated steel sheet) in a case where a sheet (steel sheet la) is used as the steel 1, that is where a hot-dip plated steel sheet is produced will be described.
[0173]
A hot-dip plating apparatus illustrated in FIG. 1 includes a transport device that continuously transports the steel sheet la. This transport device includes a feeder 3, a winder 12, and plural transport rolls 15. In this transport device, a coil 13 (first coil 13) of the long steel sheet la is held by the feeder 3. When the first coil 13 is unwound by the feeder 3, the steel sheet la is transported to the winder 12 while being supported by the transport rolls 15. Further, the steel sheet la is wound by the winder 12, and this winder 12 holds a coil 14 (second coil 14) of the steel sheet la.
[0174]
70

In the hot-dip plating apparatus, a heating furnace 4, an annealing and cooling unit 5, a snout 6, a pot 7, spray nozzles 9, a cooling device 10, and a temper rolling and shape correcting device 11 are sequentially provided in order from the upstream side of a transport path of the steel sheet la transported by the transport device. The heating furnace 4 heats the steel sheet la. This heating furnace 4 is composed of a non-oxidizing furnace. The annealing and cooling unit 5 thermally anneals the steel sheet la, followed by cooling. The annealing and cooling unit 5 is connected to the heating furnace 4, and an annealing furnace and a cooling zone (cooler) are provided on the upstream side and downstream side thereof, respectively. In this annealing and cooling unit 5, a reducing atmosphere is held. The snout 6 is a tubular member through which the steel sheet la is transported. One end of the snout 6 is connected to the annealing and cooling unit 5, and the other end thereof is aiTanged in the hot-dip plating bath 2 inside the pot 7. Similarly to the inside of the annealing and cooling unit 5, a reducing atmosphere is held in the snout 6. The pot 7 is a container containing the hot-dip plating bath 2, and a sync roll 8 is arranged inside the pot 7. The spray nozzles 9 spray gas toward the steel sheet la. The spray nozzles 9 are arranged above the pot 7. The spray nozzles 9 are arranged at a position where gas can be sprayed toward both surfaces of the steel sheet la which is pulled from the pot 7. The cooling device 10 cools a hot-dip plating metal attached onto the steel sheet. As this cooling device 10, for example, an air cooler or a mist cooler is provided. The steel sheet la is cooled by the cooling device 10. The temper rolling and shape correcting device 11 performs the temper rolling and shape correcting of the steel sheet la on which the plating layer 23 is formed. The temper rolling and shape correcting device 11 includes a skin pass mill or the like used to perform temper rolling on the steel sheet la and a tension leveler or the like used to perform shape correction on the
71

steel sheet la after temper rolling.
[0175]
In the hot-dip plating treatment using the hot-dip plating apparatus, first, the steel sheet la is unwound from the feeder 3 and continuously fed. After being heated in the heating furnace 4, the steel sheet la is transported to the annealing and cooling unit 5 in the reducing atmosphere. And at the same time is tempered by the annealing furnace, the steel sheet la is subjected to surface cleaning such as removal of rolling oil, which is attached onto the surface of the steel sheet la, or removal of an oxide film by reduction, and then is cooled in the cooling zone. Next, the steel sheet la passes through the snout 6, enters the pot 7, and is dipped in the hot-dip plating bath 2 inside the pot 7. A transport direction of the steel sheet la is changed upward by the sync roll 8 supporting the steel sheet la in the pot 7. Then, the steel sheet la is pulled from the hot-dip plating bath 2. As a result, the hot-dip plating metal is attached onto the steel sheet la.
[0176]
Next, the amount of the hot-dip plating metal attached onto the steel sheet la is controlled by spraying gas from the spray nozzles 9 to both surfaces of the steel sheet 1 a. Such a method of controlling the attached amount by gas spraying is called a gas wiping method. It is preferable that the total amount of the hot-dip plating metal attached onto both surfaces of the steel sheet la be controlled to be in a range from 40 gW to 200 g/ml
[0177]
In the gas wiping method, examples of a kind of the gas (wiping gas) sprayed toward the steel sheet la include air, nitrogen, argon, helium, and water vapor. These wiping gases may be sprayed toward the steel sheet la after being preliminarily heated.
- 72

In the embodiment, by using the hot-dip plating bath 2 having the specific composition, the oxidation and concentration of Mg on the surface of the hot-dip plating metal (the oxidation of Mg and increase in Mg concentration on the surface of the hot-dip plating metal) is fundamentally suppressed. Therefore, even if the wiping gas or the air stream generated by the spraying of the wiping gas contains oxygen, the plated amount (amount of the hot-dip plating metal attached onto the steel sheet la) can be adjusted without impairing the effects of the present invention.
[0178]
Of course, the method of controlling the plated amount is not limited to the gas wiping method, and various methods of controlling the plated amount can be used. Examples of the methods of controlling the plated amount other than the gas wiping method include a roll squeezing method including causing the steel sheet la to pass through a gap between a pair of rolls which are arranged immediately above a bath surface of the hot-dip plating bath 2; a wiping method including arranging a shield plate near the steel sheet la, which is pulled from the hot-dip plating bath 2, to wipe the hot-dip plating metal with the shield plate; an electromagnetic Vviping method including applying a force to the hot-dip plating metal, which is attached onto the steel sheet la, so as to move downward using an electromagnetic force; and a method of controlling the attached amount by using free-fall without applying an external force. Two or more methods of controlling the plated amount may be combined.
[0179]
Next, the steel sheet la is transported above an arrangement position of the spray nozzles 9 and then is turned back downward by being supported by the two transport rolls 15. That is, the steel sheet la is transported along an inverted Li-shaped path. On the inverted U-shaped path, the steel sheet 1 a is cooled in the
- 73

((H

cooling device 10 by air-cooling, mist-cooling, or the like. As a result, the hot-dip plating metal attached onto the surface of the steel sheet la is solidified, and thus the plating layer 23 is formed.
[0180]
In order to completely finish the solidification of the hot-dip plating metal by cooling it with the cooling device 10, it is preferable that the steel sheet la be cooled by the cooling device 10 such that a surface temperature of the hot-dip plating metal (or the plating layer 23) is lower than or equal to 300°C. The surface temperature of the hot-dip plating metal is measured by, for example, a radiation thermometer. In order to form such a plating layer 23, it is preferable that a cooling rate until the surface of the hot-dip plating metal on the steel sheet la is cooled to 300°C after being pulled from the hot-dip plating bath 2 be in a range from 5°C/sec to 100°C/sec. In order to control the cooling rate of the steel sheet la, it is preferable that the cooling device 10 have a temperature controlling function for controlling the temperature of the steel sheet la according to a transport direction and a sheet width direction thereof The cooling device 10 may be divided into plural pieces along the transport direction of the steel sheet la. In FIG. 1, a primary cooling device 101 for cooling the steel sheet la is provided on a path located above the arrangement position of the spray nozzles 9, and a secondary cooling device 102 for cooling the steel sheet la is provided on the downstream side of the primary cooling device 101. The primary cooling device 101 and the secondary cooling device 102 may be fiirther divided into plural pieces. In this case, for example, a configuration can be adopted in which the steel sheet la is cooled by the primary cooling device 101 such that the surface of the hot-dip plating metal is cooled to 300°C or lower, and the steel sheet la is cooled by the secondary cooling device 102 such that the temperature is lower thnn nr equal to
74

%

100°C when being introduced into the temper rolling and shape correcting device 11.
[0181]
In the process of cooling the steel sheet la, when the surface temperature of the hot-dip plating metal on the steel sheet la is higher than or equal to 500°C, it is preferable that a cooling rate of the surface of the hot-dip plating metal be slower than or equal to 50 °C/sec. In this case, particularly, the precipitation of the Si-Mg phase on the surface of the plating layer 23 is suppressed, thereby suppressing running. The reason why the cooling rate in this temperature range affects the precipitation behavior of the Si-Mg phase is not clear at this moment, but is considered to be as follows. When the cooling rate in this temperature range is fast, a temperature gradient in a thickness direction of the hot-dip plating metal is large. Therefore, the precipitation of the Mg-Si layer is preferentially promoted on the surface of the hot-dip plating metal having a low temperature. As a result, a precipitation amount of the Si-Mg phase on the outermost plating surface is increased. The cooling rate in this temperature range is more preferably slower than or equal to 40 °C/sec and still more preferably slower than or equal to 35 °C/sec.
[0182]
After cooling, the steel sheet la is subjected to temper rolling in the temper rolling and shape correcting device 11, followed by shape correcting. A rolling reduction after temper rolling is preferably in a range from 0.3% to 3%. The elongation ratio of the steel sheet la after shape correction is preferably 3% or lower.
[0183]
Next, the steel sheet la is wound by the winder 12, and the coil 14 of the steel sheet la is held in the winder 12.

CLAIMS
1. A painted plated-steel comprising:
a steel; and
a coating material that is provided on a surface of the steel,
wherein the coating material includes, in an order from the steel, a plating
layer, a coated base treatment layer that is formed on a surface of the plating layer, and
an organic coating layer that is formed on a surface of the coated base treatment layer,
the plating layer contains Al, Zn, Si, Mg, and Cr as constituent elements in
which an Al content is 25 mass% to 75 mass%, a Mg content is 0.1 mass% to 10
mass% and a Cr content is 0.02 mass% to 1.0 mass%,
the plating layer contains 0.2 vol% to 15 vol% of a Si-Mg phase,
a mass ratio of Mg in the Si-Mg phase to a total amount of Mg in the plating
layer is 3% to 100%,
the coated base treatment layer contains an organic resin and an organosilicon
compound,
the organosilicon compound has an alkylene group, a siloxane bond, and a
crosslinkable functional group expressed by -SiR R R ,
each of two of R', R", and R^ is an alkoxy group or a hydroxy group,
1 9 "^
the remaining one of R , R , and R is an alkoxy group, a hydroxy group, or a
methyl group,
the organosilicon compound accounts for 2 to 1500 parts by mass with respect
to 100 parts by mass of the organic resin, and
a thickness of the organic coating layer is 0.2 to 100 ).un.
2. The painted plated steel according to Claim 1,
1 -
20 Ft5 MU
cRicm^h 1 9 ' 7 5 ^'• ••'14?
wherein a Mg content in any region having a diameter of 4 mm and a depth of
50 nm inside an outermost layer, which is located at a depth of 50 nm from the surface
of the plating layer, is 0 mass% to less than 60 mass%.
3. The painted plated-steel according to Claim 1 or 2,
wherein a ratio of the Si-Mg phase on the surface of the plating layer is 0% or
higher and 30% or less in terms of area ratio.
4. The painted plated-steel according to any one of Claims 1 to 3.
wherein the coated base treatment layer contains one or moic types selected
from a zirconium compound and a titanium compound.
5. The painted plated-steel according to Claim 4,
wherein, in the coated base treatment layer, one or more types selected firom
the zirconium compound and the titanium compound account for 50 to 3333 parts by
mass with respect to 100 parts by mass of the organic resin.
6. The painted plated-steel according to Claim 4,
wherein, in the coated base treatment layer, one or more types selected from
the zirconium compound and the titanium compound account for 1 to 50 parts by mass
with respect to 100 parts by mass of the organic resin.
7. The painted plated-steel according to any one of Claims 1 to 6,
wherein the coated base treatment layer further contains 0.5 to 100 parts by
mass of silica with respect to 100 parts by mass of the organic resin.
2 -
-