1. A pipe provided with a corrosion prevention layer on an outside surface thereof, wherein: the corrosion prevention layer is formed on a surface of a pipe made of an iron-base material; and the corrosion prevention layer comprises either one of a Zn-Sn alloy sprayed coating comprising Sn in a content of more than 1% by mass and less than 50% by mass and a balance composed of Zn and a Zn-Sn-Mg alloy sprayed coating comprising Sn in a content of more than 1% by mass and less than 50% by mass, Mg in a content of more than 0.01% by mass and less than 5% by mass and a balance composed of Zn.

2. The pipe provided with a corrosion prevention layer on the outside surface thereof, according to claim 1, wherein: the alloy sprayed coating of the corrosion prevention layer comprises at least any one of Ti, Co, Ni and P; and a content of each of Ti, Co, Ni and P is more than 0.001% by mass and less than 3% by mass.

3. A process for production of a pipe provided with a corrosion prevention layer on an outside surface thereof, wherein the process comprising, when the pipe provided with a corrosion prevention layer on the outside surface thereof according to claim 1 is produced, heat treating the alloy sprayed coating at a temperature equal to or higher than a eutectic temperature of the alloy and lower than the melting point of the alloy.

4. A process for production of a pipe provided with a corrosion prevention layer on the outside surface thereof, wherein the process comprising, when the pipe provided with a corrosion prevention layer on the outside surface thereof according to claim 1 is produced: using one of a Zn-Sn wire, a Zn-Sn-Mg wire and a wire produced by comprising at least any one of Ti, Co, Ni and P in one of a Zn-Sn wire and a Zn-Sn-Mg wire as a first wire and a Zn wire as a second wire; and simultaneously arc spraying the first wire and the second wire.

5. A process for production of a Zn-Sn-Mg alloy wire, wherein the process comprising: melting a material comprising Sn in a content of more than 1% by mass and less than 50% by mass, Mg in a content of more than 0.01% by mass and less than 5% by mass and a balance composed of Zn; and cooling a molten alloy under solidification, obtained by the melting, at a cooling rate of 20°C/sec or more from a temperature equal to or higher than the eutectic temperature of a Zn-Sn-Mg alloy down to a temperature of 50°C or lower while the molten alloy is being solidified so as to yield a wire rod type cast product with a continuous casting machine.

6. The process for production of a Zn-Sn-Mg alloy wire according to claim 5, wherein cooling water is sprayed onto the molten alloy under solidification so as to yield a wire rod type cast product.

7. A Zn-Sn alloy for spraying comprising Sn in a content of more than 1% by mass and less than 50% by mass and a balance composed of Zn.

8. The Zn-Sn alloy for spraying according to claim 7, said alloy further comprising at least any one of Ti, Co, Ni and P, wherein a content of each of Ti, Co, Ni and P is more than 0.001% by mass and less than 3% by mass.

9. A Zn-Sn-Mg alloy for spraying comprising Sn in a content of more than 1% by mass and less than 50% by mass, Mg in a content of more than 0.01% by mass and less than 5% by mass and a balance composed of Zn.

10. The Zn-Sn-Mg alloy for spraying according to claim 9, said alloy further comprising at least any one of Ti, Co, Ni and P, wherein a content of each of Ti, Co, Ni and P is more than 0.001% by mass and less than 3% by mass.

11. An alloy wire composed of the Zn-Sn alloy for spraying according to any one of claims 7 and 8 or the Zn-Sn-Mg alloy for spraying according to any one of claims 9 and 10. Disclosed is a pipe made of an iron-base material, having a corrosion prevention layer formed on the surface thereof. The corrosion prevention layer includes a Zn-Sn sprayed coating including Sn in a content of more than 1% by mass and less than 50% by mass and the balance composed of Zn. Alternatively, the corrosion prevention layer includes a Zn-Sn-Mg sprayed coating including Sn in a content of more than 1% by mass and less than 50% by mass, Mg in a content of more than 0.01% by mass and less than 5% by mass and the balance composed of Zn. Preferably, the sprayed coating of the corrosion prevention layer includes at least any one of Ti, Co, Ni and P, and the content of each of these elements is more than 0.001% by mass and less than 3% by mass.

Description
PIPE PROVIDED WITH CORROSION PREVENTION LAYER ON THE
OUTSIDE SURFACE, PROCESS FOR PRODUCTION OF THE SAME, AND
PROCESS FOR PRODUCTION OF ALLOY WIRES USED FOR THE
CORROSION PREVENTION LAYER
Technical Field
[0001]
The present invention relates to a pipe provided with
a corrosion prevention layer on the outside surface
thereof, a process for production of the pipe and a
process for production of alloy wires used for the
corrosion prevention layer, in particular, a pipe
provided with a corrosion prevention layer on the outside
surface thereof wherein the corrosion prevention layer is
formed with a metal sprayed coating on the surface of the
pipe made of an iron-base material, such as a cast-iron
pipe, a process for production of the pipe, and a process
for production of alloy wires to be used for the
corrosion prevention layer.
Background Art
[0002]
Metal pipes practically used as laid underground have
been provided with tar or bitumen coating since long ago
for the purpose of corrosion prevention. When the coating
of a metal pipe is scratched, however, the corrosion of
the metal pipe progresses from the scratched portions.
For the purpose of solving such a corrosion problem, the
following corrosion prevention is widely applied: a metal
coating having a higher ionization tendency than the
ionization tendency of the material of a metal pipe is
formed on the surface of the metal pipe, the metal
coating undergoes the generation of a sacrificial anode

function due to the ionization tendency difference, and
thus the metal coating prevents the corrosion starting
from the scratched portions. Zinc is a typical metal
having such a sacrificial anode function. A zinc coating
is formed on the surface of a metal pipe such as an iron
pipe by plating or spraying. Such a coating is used, as
it is, as the outermost surface layer, or as it is
further overcoated with another layer. Zinc has a high
ionization tendency; the electrochemical potential
difference between iron and zinc is large, and
accordingly, in a case where zinc is used in combination
with an iron-base metal, even when some scratches are
caused in the coating, the sacrificial anode function is
displayed and the corrosion in the scratched portions can
be suppressed. In the case of cast-iron pipes widely used
as water and sewage pipelines, the coating is covered
with a polyethylene sheet referred to as a polyethylene
sleeve to block the coating from the external environment,
and consequently the corrosion prevention effect is
further enhanced.
[0003]
However, zinc has a high ionization tendency, and
hence zinc hardly maintains the sacrificial anode
function over a long period of time. As a solution to
solve this problem, the increase of the zinc coating
amount is an effective technique. However, in this case,
in addition to the increase of the material cost, the
work time is increased and the production efficiency is
also degraded.
[0004]
Alternatively, as another method, a zinc-aluminum
alloy is used (WO94/19640) as the case may be. The
addition of aluminum alleviates the ionization, and
consequently the retention time of the sacrificial anode
effect is maintained over a longer period of time.

[0005]
However, as for aluminum, health concern is raised
from some viewpoints, and the safety of aluminum as a
material applied to drink water supply pipes is not
established. For example, in a pipe joint having an
inserting-receiving structure in which the inside of a
socket formed at one end of a pipe receives a spigot
formed at one end of another pipe, the outer surface of
the spigot is brought into contact with tap water, thus
causing a possibility that aluminum is eluted from the
outer surface of the spigot.
Disclosure of the Invention
Problems to be Solved by the Invention
[0006]
An object of the present invention is to provide a
solution enabling to solve the above-described technical
problems without drastically increasing the coating
amount or without using aluminum.
Means for Solving the Problems
[0007]
For the purpose of achieving the above-described
object, the pipe provided with a corrosion prevention
layer on the outside surface thereof, of the present
invention, is a pipe wherein: the corrosion prevention
layer is formed on the surface of the pipe made of an
iron-base material; and the corrosion prevention layer
includes either one of a Zn-Sn alloy sprayed coating
including Sn in a content of more than 1% by mass and
less than 50% by mass and the balance composed of Zn and
a Zn-Sn-Mg alloy sprayed coating including Sn in a
content of more than 1% by mass and less than 50% by mass,
Mg in a content of more than 0.01% by mass and less than
5% by mass and the balance composed of Zn.

[0008]
The alloy sprayed coating of the corrosion prevention
layer of the pipe provided with a corrosion prevention
layer on the outside surface thereof of the present
invention, preferably includes at least any one of Ti, Co,
Ni and P, and the content of each of Ti, Co, Ni and P is
more than 0.001% by mass and less than 3% by mass.
[0009]
A process for production of a pipe provided with a
corrosion prevention layer on the outside surface thereof
of the present invention includes, when the pipe provided
with a corrosion prevention layer on the outside surface
thereof is produced, heat treating the alloy sprayed
coating at a temperature equal to or higher than the
eutectic temperature of the alloy and lower than the
melting point of the alloy.
[0010]
Another process for production of a pipe provided
with a corrosion prevention layer on the outside surface
thereof of the present invention includes, when the pipe
provided with a corrosion prevention layer on the outside
surface thereof is produced, using one of a Zn-Sn wire, a
Zn-Sn-Mg wire and a wire produced by including at least
any one of Ti, Co, Ni and P in one of a Zn-Sn wire and a
Zn-Sn-Mg wire as a first wire and a Zn wire as a second
wire; and simultaneously arc spraying the first wire and
the second wire.
[0011]
A process for production of an alloy wire of the
present invention includes: melting a material including
Sn in a content of more than 1% by mass and less than 50%
by mass, Mg in a content of more than 0.01% by mass and
less than 5% by mass and the balance composed of Zn; and
cooling the molten alloy under solidification, obtained
by the melting, at a cooling rate of 20°C/sec or more from

a temperature equal to and higher than the eutectic
temperature of the Zn-Sn-Mg alloy down to a temperature
of 50°C or lower while the molten alloy is being
solidified so as to yield a wire rod type cast product
with a continuous casting machine.
[0012]
According to the process for production of an alloy
wire of the present invention, cooling water is
preferably sprayed onto the molten alloy under
solidification so as to yield a wire rod type cast
product.
Advantages of the Invention
[0013]
According to the pipe provided with a corrosion
prevention layer on the outside surface thereof of the
present invention, the corrosion prevention layer on the
outside surface of a pipe made of an iron-base material
includes a Zn-Sn alloy sprayed coating or a Zn-Sn-Mg
alloy sprayed coating, and hence the corrosion prevention
performance can be drastically improved as compared to a
pipe using a simple zinc sprayed coating; additionally,
Al is not used and hence no problems associated with
health are caused. Moreover, Sn, which is soft, is used,
and hence the Zn-Sn alloy or the Zn-Sn-Mg alloy can be
easily worked into a Zn-Sn wire or a Zn-Sn-Mg wire,
respectively, and consequently a spray material can be
formed without any problem.
[0014]
According to the present invention, the alloy sprayed
coating includes at least any one of Ti, Co, Ni and P in
a predetermined content, and hence the corrosion
prevention performance can be more improved.
[0015]

According to the present invention, the alloy sprayed
coating is heat treated at a temperature equal to or
higher than the eutectic temperature of the alloy and
lower than the melting point of the alloy, and hence the
corrosion prevention performance can be more improved.
[0016]
According to the present invention, one of a Zn-Sn
wire, a Zn-Sn-Mg wire and a wire produced by including at
least any one of Ti, Co, Ni and P in one of a Zn-Sn wire
and a Zn-Sn-Mg wire is used as a first wire and a Zn wire
is used as a second wire, and simultaneously the first
wire and the second wire are arc sprayed, and hence the
corrosion prevention performance can be furthermore
improved.
[0017]
According to the present invention, a molten Zn-Sn-Mg
alloy under solidification is quenched from a temperature
equal to or higher than the eutectic temperature of the
Zn-Sn-Mg alloy down to a temperature of 50°C or lower
while the molten alloy is being solidified so as to yield
a wire rod type cast product with a continuous casting
machine, and hence the zinc crystals can be refined, and
accordingly the mechanical properties of the alloy wire
can be improved. Thus, a Zn-Sn-Mg alloy wire to be hardly
broken in a wiredrawing step can be produced.
Brief Description of the Drawings
[0018]
FIG. 1 is a view illustrating a production apparatus
used for a process of production of an alloy wire of the
present invention;
FIG. 2 is a view illustrating a bending test method
based on the present invention;
FIG. 3 is a view showing a result of an optical
microscope observation of the microstructure of a

specimen produced under the conditions without water
cooling; and
FIG. 4 is a view showing a result of an optical
microscope observation of the microstructure of a
specimen produced under the conditions with water cooling.
Best Mode for Carrying Out the Invention
[0019]
The pipe provided with a corrosion prevention layer
on the outside surface thereof of the present invention
is a pipe in which a corrosion prevention layer including
an alloy sprayed coating is formed on the surface of a
pipe made of an iron-base material, such as a cast-iron
pipe.
[0020]
In a first aspect of the present invention, the alloy
sprayed coating is formed with a Zn-Sn alloy sprayed
coating including Sn in a content of more than 1% by mass
and less than 50% by mass and the balance composed of Zn.
By adopting an alloy sprayed coating formed by adding Sn
to predominant Zn, the corrosion prevention performance
can be improved as compared to a sprayed coating using
only Zn. The corrosion prevention performance of the Zn-
Sn alloy sprayed coating can be made approximately the
same as the corrosion prevention performance of Zn-15A1
(Zn: 85% by mass, Al: 15% by mass). When the content of
Sn is 1% by mass or less, or when the content of Sn is
50% by mass or more, no substantial improvement effect of
the corrosion prevention performance due to the addition
of Sn can be obtained.
[0021]
The inclusion of Sn also provides an advantage that
white rust, namely, a corrosion product of Zn hardly
occurs. In the case where white rust tends to occur, when
a product having a black paint coating applied onto a

sprayed coating is stored outdoors and white rust is
generated in the black paint coating portion, such white
rust shows up so clearly to result in a problem that
recoating is necessary at the time of shipping.
[0022]
The inclusion of Sn, which is a soft material, also
provides an advantage that the production of the Zn-Sn
alloy wire as a material for spraying is facilitated.
Additionally, such a Zn-Sn alloy includes only Zn and Sn,
and hence causes no problem associated with health.
[0023]
In a second aspect of the present invention, the
alloy sprayed coating is formed with a Zn-Sn-Mg alloy
sprayed coating including Sn in a content of more than 1%
by mass and less than 50% by mass, Mg in a content of
more than 0.01% by mass and less than 5% by mass and the
balance composed of Zn.
[0024]
Also in this case, as compared to a sprayed coating
using only Zn, the corrosion prevention performance can
be improved. The corrosion prevention performance of the
Zn-Sn-Mg alloy sprayed coating can be made approximately
the same as or higher than the corrosion prevention
performance of Zn-15A1 (Zn: 85% by mass, Al: 15% by mass).
[0025]
When the content of Sn is 1% by mass or less and/or
when the content of Mg is 0.01% by mass or less, no
substantial improvement effect of the corrosion
prevention performance due to the addition of Sn and Mg
can be obtained. On the other hand, also when the content
of Sn is 50% by mass or more and/or when the content of
Mg is 5% by mass or more, similarly no substantial
improvement effect of the corrosion prevention
performance due to the addition of Sn and Mg can be
obtained.

[0026]
In the same manner as in the formation of the Zn-Sn
alloy sprayed coating, the formation of the Zn-Sn-Mg
alloy sprayed coating also provides the advantages that
white rust hardly occurs, wires are easily produced and
no problem associated with health occurs.
[0027]
In the alloy sprayed coatings of the first and second
aspects of the present invention, at least any one of Ti,
Co, Ni and P can be included; in other words, any one, or
any two to four, in combination, of these elements can be
included. The content of each of these elements is
preferably 0.001% by mass or more and 3% by mass or less.
The inclusion of these elements in addition to Sn or Sn-
Mg correspondingly reduces the amount of Zn.
[0028]
The inclusion of these elements enables to further
improve the corrosion prevention performance. However,
when the content of each of these elements is less than
0.001% by mass, no substantial improvement effect of the
corrosion prevention performance due to the addition of
these elements can be obtained. On the other hand, also
when the content of each of these elements is more than
3% by mass, no substantial improvement effect of the
corrosion prevention performance due to the addition of
these elements can be obtained.
[0029]
In the same manner as described above, the inclusion
of these elements provides the advantages that white rust
hardly occurs, and because of the small contents of these
elements, alloy wires can be produced without problems
and no problem associated with health occurs.
[0030]
The pipe provided with a corrosion prevention layer
on the outside surface thereof of the present invention

is a pipe in which the corrosion prevention layer
includes the above-described alloy sprayed coating. The
corrosion prevention layer is particularly preferably
such that in addition to the alloy sprayed layer, another
coating such as an overcoating is laminated on the alloy
sprayed coating. The overcoating can be performed with an
acrylic resin coating material or an epoxy resin coating
material.
[0031]
Next, description is made on the process for
production of a pipe provided with a corrosion prevention
layer on the outside surface thereof of the present
invention, namely, the process for formation of an alloy
sprayed coating. Examples of the process for formation of
an alloy sprayed coating on the surface of a cast-iron
pipe may include a known spraying method, namely, a
method in which a Zn-Sn wire, a Zn-Sn-Mg wire or a wire
produced by adding at least any one of Ti, Co, Ni and P
to one of these wires is used and an arc spraying is
applied. Alternatively, a spraying with an alloy powder,
instead of a wire, can also be adopted.
[0032]
As an alternative to the above description, the Zn-Sn
alloy sprayed coating is also able to be obtained by a
technique in which a Zn-Sn wire or a wire produced by
adding to this wire at least any one of Ti, Co, Ni and P
is used as a first wire and a Zn wire is used as a second
wire, and simultaneously the first wire and the second
wire are arc sprayed. Similarly, the Zn-Sn-Mg alloy
sprayed coating is also able to be obtained by a
technique in which a Zn-Sn-Mg wire or a wire produced by
adding to this wire at least any one of Ti, Co, Ni and P
is used as a first wire and a Zn wire is used as a second
wire, and simultaneously the first wire and the second
wire are arc sprayed.

[0033]
For example, for the purpose of obtaining a Zn-25Sn-
0.5Mg (Sn: 25% by mass, Mg: 0.5% by mass, Zn: the
balance; hereinafter, similar representations are adopted,
as the case may be) alloy sprayed coating, instead of
performing a simultaneous arc spraying by using two
strings of a Zn-25Sn-0.5Mg wire, a simultaneous arc
spraying by using a Zn-50Sn-1.0Mg wire and a Zn wire in
equal amounts can also be performed.
[0034]
In this way, the corrosion prevention performance can
be further improved. On the other hand, the use amount of
the Zn-Sn-Mg wire can be halved, and hence the cost
required for the preparation of the wire can be reduced.
[0035]
The reason for the fact that the adoption of such a
spray method further improves the corrosion prevention
performance is not clear, but can be probably attributed
to each of or a synergetic effect of the following (a),
(b) and (c).
[0036]
(a) For example, when the simultaneous arc spraying
is performed by using the Zn-Sn-Mg alloy wire and the Zn
wire, the Zn-Sn-Mg alloy and Zn are both distributed in
the sprayed coating thus formed. In this case, the Zn-Sn-
Mg alloy is lower in electric potential than Zn, and when
the Zn-Sn-Mg alloy and Zn each function as a sacrificial
anode, the Zn-Sn-Mg alloy preferentially begins to be
eluted. The thus eluted Zn-Sn-Mg alloy forms another
relatively stable coating on the surface of the coating,
this stable coating probably suppresses the consumption
or elution of the rest of the Zn-Sn-Mg alloy and Zn, and
thus the corrosion prevention performance is probably
further improved.
[0037]

(b) The presence of Zn in the coating offers a
physical hindrance to suppress the elution of the Zn-Sn-
Mg alloy, alternatively in the case where the Zn-Sn-Mg
alloy is eluted, the corrosion product of the Zn-Sn-Mg
alloy suppresses the elution of Zn, and thus the
corrosion prevention performance is probably further
improved.
[0038]
(c) According to the observation of the present
inventors, the porosity of a Zn-25Sn-0.5Mg sprayed
coating obtained by using two stirrings of a Zn-25Sn-
0.5Mg wire was found to be about 15%; on the other hand,
the porosity of another Zn-25Sn-0.5Mg sprayed coating
obtained by using a Zn-50Sn-l.OMg wire and the Zn wire in
equal amounts was found to be about 12%. In other words,
from the lower porosity of the latter coating, the
corrosion prevention performance is probably improved in
the latter coating. The lower porosity may be attributed
to the effect of the use of the wires different in
hardness from each other on the basis of the fact that
the Zn-50Sn-1.0Mg wire is softer than the Zn wire.
[0039]
In the production of the pipe provided with a
corrosion prevention layer on the outside surface thereof
of the present invention, preferably an alloy sprayed
coating is formed on a cast-iron pipe, and then the alloy
sprayed coating is heat treated at a temperature equal to
or higher than the eutectic temperature (198°C) of the
alloy and lower than the melting point of the alloy. The
application of such a heat treatment enables to further
improve the corrosion prevention performance. This is
presumably because only Sn is melted by the heat
treatment at a temperature higher than the eutectic
temperature of the Zn-Sn alloy or the Zn-Sn-Mg alloy,
thus the fine voids having been created in the sprayed

coating are filled with the molten Sn, and consequently a
cast-iron pipe provided with such a coating is capable of
suppressing the penetration of electrolytes into the
coating when the cast-iron pipe is laid underground.
[0040]
Accordingly, a heat treatment at a temperature lower
than the eutectic temperature substantially does not melt
Sn, and hence the above-described effect is not able to
be obtained. On the other hand, the heat treatment
temperature is higher than the melting point of the alloy
sprayed coating, the oxidation of the alloy is made to
progress and the intrinsic corrosion prevention
performance is lost.
[0041]
The heat treatment time is not particularly limited;
however, the heat treatment time is preferably 1 second
to 60 minutes. When the heat treatment time is shorter
than this range, the treatment time is insufficient and
no necessary heat treatment can be performed.
[0042]
When the above-described overcoating is performed,
the overcoating is performed after the alloy sprayed
coating is formed.
[0043]
Hereinafter, the process for production of the Zn-Sn-
Mg alloy wire is described.
[0044]
Various processes for production of alloy wires for
use in metal spray have been known. However, any common
production processes include a wiredrawing step in which
a wire having a predetermined cross-sectional shape is
drawn to be worked into an alloy wire having a
predetermined wire diameter. In other words, a working
step of reducing the diameter of a wire is included. In
this case, when the material for the wire is low in

strength or ductility, wire breakage may occur. For the
purpose of coping with such breakage, a treatment such as
a heat treatment may be performed depending on the
material for the wire. In particular, in the case of the
Zn-Sn-Mg alloy wire, when the content of Sn is small, the
wire is somewhat brittle, accordingly the workability is
degraded and hence the wire breakage may occur in the
wiredrawing step as described above.
[0045]
The process for production of the Zn-Sn-Mg alloy wire
of the present invention is a production process which
hardly causes wire breakage in the wiredrawing step.
[0046]
This production process, as described above,
includes: melting a material including Sn in a content of
more than 1% by mass and less than 50% by mass, Mg in a
content of more than 0.01% by mass and less than 5% by
mass and the balance composed of Zn; and cooling the
molten alloy under solidification, obtained by the
melting, at a cooling rate of 20°C/sec or more from a
temperature equal to or higher than the eutectic
temperature of the Zn-Sn-Mg alloy down to a temperature
of 50°C or lower while the molten alloy is being
solidified so as to yield a wire rod type cast product
with a continuous casting machine. In this way, the zinc
crystals can be refined to improve the mechanical
properties of the alloy wire. Consequently, a Zn-Sn-Mg
alloy wire which is hardly broken in the wiredrawing step
can be produced.
[0047]
The details of this production process are described.
FIG. 1 illustrates the configuration of a production
apparatus for embodying this production process. This
apparatus includes a continuous casting machine 101 and a
take-up unit 102. In the casting machine 101, a groove

112 having a U-shaped cross-section is formed on the
circumference of the rotary casting wheel 111. A crucible
115 is disposed above the casting wheel 111. The crucible
115 is capable of storing the molten alloy 103 of the Zn-
Sn-Mg alloy in the interior thereof and a molten alloy
outlet 116 is formed at the bottom of the crucible 115.
In the vicinity of the crucible 115, a spray nozzle 113
is disposed, and the spray nozzle 113 is equipped with a
spout 114 for spraying cooling water.
[0048]
In the production, while the casting wheel 111 is
being rotated slowly, the molten alloy 103 is fed to the
portion of the groove 112 which portion is located on the
top of the casting wheel 111, from the crucible 115. Then,
the molten alloy 103 begins to be solidified due to the
heat removal by the casting wheel 111. Immediately after
the start of the solidification, cooling water is sprayed
from the spray nozzle 113 onto the molten alloy 104 under
solidification inside the groove 112.
[0049]
In this way, the molten alloy 104 under
solidification is quenched to produce an alloy wire 105.
The alloy wire 105 is formed by the quenching of the
molten alloy 104 under solidification, hence the crystals
are refined and consequently the ductility of the alloy
wire 105 can be improved. The obtained alloy wire 105 is
taken up by the take-up unit 102.
[0050]
The quenching by spraying cooling water from the
spray nozzle 113 onto the molten alloy under
solidification 104 is preferably conducted as immediately
as possible after the casting of the molten alloy 103
into the groove 112. For the purpose of attaining the
improvement of the ductility due to the crystal refining,
it is required to adopt the cooling conditions that the

cooling is performed at a cooling rate of 20°C/sec or more
from a temperature equal to or higher than the eutectic
temperature of the Zn-Sn-Mg alloy, namely, 198°C, down to
a temperature of 50°C or lower.
[0051]
In addition to the above-described water cooling, as
long as a cooling technique can adopt the above-described
cooling conditions, the cooling technique may be an air
cooing using cold air, or alternatively a cooling using
another fluid.
[0052]
The alloy wire 105 taken up by the take-up unit 102
is subsequently subjected to the wiredrawing step.
Examples
[0053]
Hereinafter, Examples of the present invention are
described. It is to be noted that in following Examples,
Comparative Examples, the evaluations of various physical
properties were performed as follows.
[0054]
(1) Workability into wire
An alloy ingot of 47 mm in diameter x 350 mm in
length was prepared and the workability into wire was
evaluated by measuring the Vickers hardness. The alloy
ingot after the hardness measurement was forged so as to
have a reduced diameter of 10 mm and further wiredrawn so
as to have a diameter of 1.6 mm, and thus the workability
was evaluated on the basis of the following standards.
[0055]
G(Good): Wiredrawing can be performed to a diameter
of 1.6 mm.
P(Poor): Breakage occurs during wiredrawing.
(2) Corrosion resistance

A corrosion resistance test was performed in the
following manner. Specifically, a 150 mm x 70 mm x 2 mm
sand-blast steel plate was used as a specimen. On this
plate, a 20 to 30-|im thick sprayed coating was formed at
a spray amount of 130 g/m2 by an electric arc spray
technique using a wire having a diameter of 1.6 mm, and
thus a test sample was prepared. The corrosion resistance
test and the evaluation method are as follows.
[0056]
(2-1)
The salt spray test specified in JIS Z2371 was
performed. In each of the case where only the Zn-Sn alloy
was sprayed and no heat treatment was applied and the
case where only the Zn-Sn-Mg alloy was sprayed and no
heat treatment was applied, the corrosion resistance was
evaluated on the basis of the degree of white rust
occurrence and the time period until red rust occurred.
The degree of white rust occurrence was visually
evaluated on the basis of the following standards.
[0057]
G(Good): The degree of white rust occurrence is low.
A(Average): The degree of white rust occurrence is
moderate.
P(Poor): The degree of white rust occurrence is high.
(2-2)
With respect to red rust, the evaluation was
performed as follows. In the salt spray test for the case
where only Zn was sprayed and no heat treatment was
applied, the time period until red rust occurred was
defined as "1". With reference to this definition, in
each of the case where only the Zn-Sn alloy was sprayed
and the case where only the Zn-Sn-Mg alloy was sprayed,
the time period until red rust occurred in the salt spray
test was numerically evaluated for a test sample to which
no heat treatment was applied.

[0058]
(2-3)
The time period until red rust occurred in the salt
spray test was evaluated for the case where any one of Ti,
Co, Ni and P was singly added and no heat treatment was
applied. Specifically, in each of the Zn-Sn alloy free
from the addition of these elements and the Zn-Sn-Mg
alloy free from the addition of these elements, the time
period until red rust occurred without application of a
heat treatment was defined as "1"; with reference to this
definition, the time period concerned was evaluated on
the basis of the following standards.
[0059]
E (Excellent) : The time period until red rust occurred
was longer by a factor of 1.5 or more.
G(Good): The time period until red rust occurred was
longer by a factor of 1.0 or more and less than 1.5.
A(Average): The time period until red rust occurred
was approximately 1.
(2-4)
The time period until red rust occurred in the salt
spray test was evaluated for each of the case where only
the Zn-Sn alloy was sprayed without adding Ti, Co, Ni and
P and a heat treatment was applied and the case where
only the Zn-Sn-Mg alloy was sprayed without adding Ti, Co,
Ni and P and a heat treatment was applied. Specifically,
for each of the test samples subjected to a heat
treatment for 30 minutes, measurement was made on the
heat treatment temperature range in which the time period
until red rust occurred was made longer and the corrosion
prevention effect was able to be evaluated as improved as
compared to the corresponding case where no heat
treatment was applied.
[0060]
(2-5)

While a test sample free from the addition of Ti, Co,
Ni and P and free from any heat treatment was being
immersed in tap water at 30°C, the time period until red
rust occurred was evaluated. Specifically, the time
period until red rust occurred in a case where only Zn
was sprayed was defined as "1"; for the test sample, with
reference to this definition, the time period until red
rust occurred was numerically evaluated.
[0061]
(2-6)
While a test sample free from the addition of Ti, Co,
Ni and P and free from any heat treatment was being
immersed in sulfuric acid of pH 3 at 30°C, the time period
until red rust occurred was evaluated. Specifically, the
time period until red rust occurred in a case where only
Zn was sprayed was defined as "1"; for the test sample,
with reference to this definition, the time period until
red rust occurred was numerically evaluated.
[0062]
Details of Examples and Comparative Examples are as
follows.
[0063]
(Examples 1 to 6 and Comparative Examples 1 to 4)
The Zn-Sn alloys having the component compositions
shown in Table 1 were sprayed to prepare the test samples
of Examples 1 to 6 and Comparative Examples 1 to 4. The
evaluation results of these test samples are shown in
Table 1. In Comparative Examples 3, only Zn was sprayed
and in Comparative Example 4, only Sn was sprayed.

[0065]
In Examples 1 to 6 and Comparative Examples 1 to 4,
when Ti, Co, Ni and P were added and the salt spray test
was performed, in any of the cases in which any one of Ti,
Co, Ni and P was singly added, the same evaluation
results were obtained, by varying the addition amount, on
the time periods until red rust occurred. Therefore, in
Table 1, for simplicity, only one typical example is
shown for each of Examples and Comparative Examples.
Specifically, Table 1 means that in each of Examples 1 to
6 and Comparative Examples 1 to 4, for any one of Ti, Co,
Ni and P, when the addition amount thereof was varied as
0.001, 0.01, 0.1, 1 and 3% by mass, the same evaluation
results were obtained for all these elements.
[0066]
(Examples 7 to 42 and Comparative Examples 5 to 18)
The Zn-Sn-Mg alloys having the component compositions
shown in Table 2 and Table 3 were sprayed onto the
specimens to yield the test samples of Examples 7 to 42
and Comparative Examples 5 to 14. The evaluation results
of the test samples of Examples 7 to 30 are shown in
Table 2, and the evaluation results of the test samples
of Examples 31 to 42 and Comparative Examples 5 to 18 are
shown in Table 3. For reference, in each of Table 2 and
Table 3, Comparative Examples 3 and 4 are again listed.

[0069]
In Examples 7 to 42 and Comparative Examples 5 to 18,
when Ti, Co, Ni and P were added each alone and the salt
spray test was performed, the same evaluation results
were obtained, by varying the addition amount, on the
time periods until red rust occurred. Therefore, also in
Tables 2 and 3 in the same manner as in Table 1, for
simplicity, only one typical example is shown for each of
Examples 7 to 42 and Comparative Examples 5 to 18.
Specifically, this means that in each of Examples 7 to 42
and Comparative Examples 5 to 18, in any of the cases in
which any one of Ti, Co, Ni and P was added, when the
addition amount thereof was varied as 0.001, 0.01, 0.1, 1
and 3% by mass, the same results were obtained for all
these elements as shown in Tables 2 and 3.
[0070]
(Examples 43 to 53)
As shown in Table 4, in each of Examples 43 to 53, a
Zn-Sn-Mg wire was used as a first wire and a Zn wire was
used as a second wire, and simultaneously the first wire
and the second wire were arc sprayed. The results thus
obtained are shown in Table 4. In this tabular
presentation, in the same manner as in above-described
Examples, in each of Examples 43 to 53, when Ti, Co, Ni
and P were added and the salt spray test was performed,
in any of the cases in which any one of Ti, Co, Ni and P
was singly added, the same evaluation results were
obtained, by varying the addition amount, on the time
periods until red rust occurred. Therefore, also in Table
4, for simplicity, only one typical example is shown for
each of Examples 43 to 53.

[0072]
As can be seen from Table 1, in Examples 1 to 6 in
each of which a Zn-Sn alloy was sprayed, the used alloys
were able to be wiredrawn without problems and all the
used alloys were able to yield a wire of 1.6 mm in
diameter.
[0073]
In each of Examples 1 to 6, the degree of white rust
occurrence was low and, additionally the time period
until red rust occurred was long, hence sufficient
corrosion prevention performance was attained. Because of
the use of the Zn-Sn alloys, Examples 1 to 6 were free
from problems associated with health. In each of Examples
1 to 6, the time period until red rust occurred was
approximately as excellent as the time period concerned
of the heretofore known Zn-15A1 alloy. The cases where at
least any one of Ti, Co, Ni and P was added to the Zn-Sn
alloy and the cases where a heat treatment was applied
after spraying were able to further improve the corrosion
prevention property. With respect to the heat treatment,
specifically, when the heat treatment was performed at a
temperature falling in a range equal to or higher than
the eutectic temperature, namely, 198°C, of the alloy
forming the sprayed coating and lower than the melting
point of the alloy sprayed coating, the corrosion
prevention effect was able to be improved by a heat
treatment for 30 minutes; the corrosion prevention
property when immersion in tap water was made and the
corrosion prevention property when the immersion in
sulfuric acid was made were also excellent.
[0074]
On the contrary, in Comparative Example 1, the mixing
proportion of Sn was lower than the range of the present
invention, hence the mixing proportion of Zn was
correspondingly higher, and accordingly corresponding

white rust occurrence was observed. Because the mixing
proportion of Sn was lower than the range of the present
invention, Sn hardly displayed the function of
suppressing the elution of Zn, and hence the time period
until red rust occurred was extremely shorter as compared
to Examples 1 to 6.
[0075]
In Comparative Example 2, the mixing proportion of Sn
was, in contrast, larger than the range of the present
invention, but the time period until red rust occurred
was similarly shorter as compared to Examples 1 to 6.
[0076]
In Comparative Example 3, only Zn was sprayed, and
hence the degree of white rust occurrence was further
higher and the time period until red rust occurred was
also shorter as compared to Comparative Example 1.
[0077]
In Comparative Example 4, only Sn was sprayed, and
hence the time period until red rust occurred was further
shorter as compared to Comparative Example 2.
[0078]
As can be seen from Tables 2 and 3, in Examples 7 to
42 in each of which a Zn-Sn-Mg alloy was sprayed, the
used alloys were able to be wiredrawn without problems
and all the used alloys were each able to yield a wire of
1.6 mm in diameter.
[0079]
In each of Examples 7 to 42, the degree of white rust
occurrence was low and, additionally the time period
until red rust occurred was long, hence sufficient
corrosion prevention performance was attained. In each of
Examples 7 to 42, the time period until red rust occurred
was approximately as excellent as or more excellent than
the time period concerned of the known Zn-15A1 alloy. The
cases where at least any one of Ti, Co, Ni and P was

added to the Zn-Sn-Mg alloy and the cases where a heat
treatment was applied after spraying were able to further
improve the corrosion prevention property. With respect
to the heat treatment, specifically, when the heat
treatment was performed at a temperature falling in a
range equal to or higher than the eutectic temperature,
namely, 198°C, of the alloy forming the sprayed coating
and lower than the melting point of the alloy sprayed
coating, the corrosion prevention effect was able to be
improved by a heat treatment for 30 minutes; the
corrosion prevention property when immersion in tap water
was made and the corrosion prevention property when the
immersion in sulfuric acid was made were also excellent.
[0080]
On the contrary, in Comparative Example 5, as shown
in Table 3, the mixing proportion of Mg offered no
problem; however, the mixing proportion of Sn was lower
than the range of the present invention, hence the mixing
proportion of Zn was correspondingly higher and
accordingly corresponding white rust occurrence was found.
Additionally, the time period until red rust occurred was
shorter as compared to Examples 7 to 42.
[0081]
In each of Comparative Examples 6, 8, 10, 12, 14 and
16, the mixing proportion of Sn offered no problem;
however, the mixing proportion of Mg was lower than the
range of the present invention, Mg hardly displayed the
function of suppressing the elution of Zn, and hence the
time period until red rust occurred was shorter as
compared to Examples 7 to 12, 13 to 18, 19 to 24, 25 to
30, 31 to 36 and 37 to 42.
[0082]
In Comparative Examples 6, 8, 10, 12, 14 and 16 as
compared respectively to Examples 1, 2, 3, 4, 5 and 6,
which were respectively the same in the mixing

proportions of Zn and Sn as these Comparative Examples,
although a slight amount of Mg was added, the time period
until red rust occurred was made rather shorter. The
reasons for this fact are not clear; probably, the
addition amount of Mg was very small, and hence no effect
of the addition of Mg was manifested, and some factors
leading to poor results functioned.
[0083]
In each of Comparative Examples 7, 9, 11, 13, 15 and
17, the mixing proportion of Sn offered no problem;
however, the mixing proportion of Mg was higher than the
range of the present invention, and hence the corrosion
prevention property was extremely degraded. Consequently,
red rust occurred in an extremely short time period as
compared to Examples 7 to 42.
[0084]
In Comparative Example 18, the mixing proportion of
Mg offered no problem; however, the mixing proportion of
Sn was higher than the range of the present invention,
and hence the time period until red rust occurred was
shorter as compared to Examples 7 to 42.
[0085]
In Examples 43, 44, 45, 46, 47, 48, 49 and 50, for
the purpose of obtaining the coatings having the same
compositions as the compositions respectively in Examples
7, 12, 13, 18, 19, 24, 25 and 30, the Zn-Sn-Mg wires each
having a doubled amount of Sn and a doubled amount of Mg
in relation to the corresponding Example and the Zn wire
including only Zn were used. Consequently, it was
verified that in any of Examples 43 to 50, as compared to
the corresponding Examples 7, 12, 13, 18, 19, 24, 25 and
30, the time period until red rust occurred due to the
immersion in tap water and the time period until red rust
occurred due to the immersion in sulfuric acid were

longer, hence the corrosion prevention performance was
further improved.
[0086]
Also in each of Examples 51 to 53, in the same manner
as in Examples 43 to 50, the time period until red rust
occurred due to the immersion in tap water and the time
period until red rust occurred due to the immersion in
sulfuric acid were both long, hence the corrosion
prevention performance was excellent.
[0087]
Although no description is made in Tables 1 to 4, in
the case where to the Zn-Sn alloy or the Zn-Sn-Mg alloy,
at least any one of Ti, Co, Ni and P was added, and after
spraying, a heat treatment was performed at a temperature
falling in a range equal to or higher than the eutectic
temperature, namely, 198°C, of the alloy forming the
sprayed coating and lower than the melting point of the
alloy sprayed coating, the corrosion prevention property
was able to be further improved.
[0088]
(Example 54)
Hereinafter, an example of the process for production
of an alloy wire of the present invention is described.
[0089]
By using an apparatus shown in FIG. 1, under the
below-described conditions, an alloy wire 105 in which
crystals were refined, the ductility thereof was improved
and the diameter thereof was 10 mm was obtained. Then,
the alloy wire 105 was worked into an alloy wire having a
diameter of 1.6 mm with a not-shown wiredrawing machine.
[0090]
Specifically, in the above-described production
process, the timing of spraying cooling water was altered
and quenching was performed. More specifically, as shown
in Table 5, the timing of spraying cooling water

(hereinafter, referred to as "water cooling timing") was
varied, and thus the specimens 1 to 4 were produced.
[0091]
In other words, Zn, Sn and Mg were melted at 450°C,
and these molten materials were mixed in such a way that
the content of Sn was 30% by mass, the content of Mg was
0.3% by mass and the balance was composed of Zn to yield
a molten alloy. With reference to the timing (hereinafter,
referred to as "arrival timing") at which the molten
alloy 103 discharged from the molten alloy outlet 116 of
the crucible 115 shown in FIG. 1 arrived at the groove
112, the water cooling timing was varied. Specifically,
the position of the spray nozzle 113 shown in FIG. 1 was
adjusted along the rotation direction of the casting
wheel 111 so as to give a required water cooling timing.
[0092]
Each of the obtained specimens 1 to 4 was subjected
to a tensile test to measure the tensile strength and the
elongation, also subjected to a bending test to measure
the load and the breaking angle, and subjected to a
measurement of the Vickers hardness Hv; the average
values over the values obtained by six times repeated
measurements were adopted as the measurement results.
[0093]
The bending test was performed according to JIS Z
2248 "Bending test method for metal material."
Specifically, as shown in FIG. 2, the specimen 150 having
a diameter of 1.6 mm was made to take a position with the
axis direction thereof to be horizontal and was placed,
on a pair of supports 161 and 162 each having a diameter
of 10 mm and being disposed at a certain horizontal
interval, so as to bridge over this pair. A pushing metal
rod 163 having an end cross-sectional shape of a
semicircle of 5 mm in radius vertically applied a load

170 to the specimen 150 at a position between the support
161 and the support 162.
[0094]
Thus, as shown in FIG. 2, the specimen 150 was
deformed into a V-shape. At the time of the breaking of
the specimen 150 due to the deformation, the bending
angle 9 was measured, wherein the bending angle 0 was an
angle formed by the crossing of the extended line of the
portion 151 of the specimen 150 in contact with one of
the supports, namely, the support 161 and the extended
line of the portion 152 of the specimen 150 in contact
with the other of the supports, namely, the support 162.
It is to be noted that the bending angle 6 was an angle
while the load 170 was being applied, but not the angle
after the load was removed. At this time, the occurrence
and nonoccurrence of cracks, flaws and other defects in
the curved outer portion of the curved portion 153 of the
specimen 150 were examined.
[0095]
(Specimen 1)
An alloy wire produced under the conditions without
water cooling was adopted as the specimen 1. In the
specimen 1, the tensile strength was 125 N/mm2 and the
elongation was 1%; and when the bending test was
performed, the specimen 1 was broken under a load of 20 N
and at a bending angle 0 of 40 degrees. The Vickers
hardness Hv was found to be 26.
[0096]
The evaluation results for the specimen 1 are shown
in Table 5.


[0098]
(Specimen 2)
An alloy wire produced under the conditions with
water cooling was adopted as the specimen 2. The water
cooling timing was set at 30 seconds after the arrival
timing of the molten alloy 103 at the groove 112 shown in
FIG. 1. In the cooling, cooling water at normal
temperature was continuously sprayed for 5 to 10 seconds.
The temperature of the molten alloy 104 before the water
cooling was 200 to 250°C, and the temperature of the wire
105 after the water cooling was 20 to 40°C. In the
specimen 2, the tensile strength was 154 N/mm2 and the
elongation was 10%; and when the bending test was
performed, the specimen 2 was broken under a load of 25 N
and at a bending angle 0 of 150 degrees. The Vickers
hardness Hv was found to be 35.
[0099]
The evaluation results for the specimen 2 are shown
in Table 5.
[0100]
(Specimen 3)
An alloy wire produced under the conditions with
water cooling was adopted as the specimen 3. The water
cooling timing was set at 15 seconds after the above-

described arrival timing. In the cooling, cooling water
at normal temperature was continuously sprayed for 5 to
10 seconds. The temperature of the molten alloy 104
before the water cooling was 250 to 300°C, and the
temperature of the wire 105 after the water cooling was
30 to 50°C. In the specimen 3, the tensile strength was
150 N/mm2 and the elongation was 14%; and the bending test
was performed, and consequently the specimen 3 was not
broken under a load of 25 N and even at a bending angle 0
of 180 degrees. The Vickers hardness Hv was found to be
35.
[0101]
The evaluation results for the specimen 3 are shown
in Table 5.
[0102]
(Specimen 4)
An alloy wire produced under the conditions with
water cooling was adopted as the specimen 4. The water
cooling timing was set at 5 seconds after the arrival
timing. In the cooling, cooling water at normal
temperature was continuously sprayed for 5 to 10 seconds.
The temperature of the molten alloy 104 before the water
cooling was 300 to 350°C, and the temperature of the wire
105 after the water cooling was 30 to 50°C. In the
specimen 4, the tensile strength was 155 N/mm2 and the
elongation was 16%; and the bending test was performed,
and consequently the specimen 4 was not broken under a
load of 25 N and even at a bending angle 0 of 180 degrees.
The Vickers hardness Hv was found to be 35.
[0103]
The evaluation results for the specimen 4 are shown
in Table 5.
[0104]
In addition to these measurements, a microstructure
observation was also performed. FIG. 3 shows a result of

an optical microscope observation of the microstructure
of the specimen 1 produced under the conditions without
water cooling. As shown in the figure, a dendritic
microstructure generated by the dendritic precipitation
of the zinc crystals was observed. In FIG. 3, black
portions represent zinc crystals and the white portions
represent the eutectic crystals.
[0105]
FIG. 4 shows a result of an optical microscope
observation of the microstructure of the specimen 4
produced under the conditions with water cooling. As
shown in the figure, an acicular microstructure generated
by the acicular precipitation of the zinc crystals was
observed. Further, the zinc crystals were finer as
compared to the alloy wire of FIG. 3 produced under the
conditions without water cooling.
[0106]
As described above, when quenching was performed by
spraying cooling water, the mechanical properties of the
alloy wire were improved. Further, the earlier was the
timing of the cooling water spraying, the better results
were obtained. Specifically, as is clear from the
measurement results of the tensile test, the specimens 2
to 4 produced under the conditions with water cooling
were improved in tensile strength by about 20% and
drastically improved in elongation as compared to the
specimen 1 produced under the conditions without water
cooling. Additionally, the specimens 2 to 4 produced
under the conditions with water cooling were shown to be
hardly broken, from the measurement results of the
bending test, and the specimens 2 to 4 each showed a high
Vickers hardness value.
[0107]
Among the alloy wires produced in the similar manner
under the conditions with water cooling, the specimen 3

for which the timing of the cooling water spraying was
earlier than for the specimen 2 was more hardly broken
than the specimen 2; the specimen 4 for which the timing
of the cooling water spraying was earlier than for the
specimen 3 was larger in elongation than the specimen 3.
[0108]
Consequently, as described above, in the working of
an alloy wire having a diameter of 10 mm into an alloy
wire having a diameter of 1.6 mm with a wiredrawing
machine, the occurrence of the wire breaking was observed
when the specimen 1 produced under the conditions without
water cooling was obtained, but no wire breaking occurred
when the specimens 2 to 4 produced under the conditions
with water cooling were obtained.
[0109]
As described above, the production under the
conditions with water cooling enabled to refine the zinc
crystals and enabled to improve the mechanical properties
of the alloy wire. Further, the adoption of the earlier
timing of the cooling water spraying enabled to promote
the refinement of the zinc crystals and to improve, in
particular, the ductility.

We Claim:
1. A pipe provided with a corrosion prevention layer on
an outside surface thereof, wherein:
the corrosion prevention layer is formed on a surface
of a pipe made of an iron-base material; and
the corrosion prevention layer comprises either one
of a Zn-Sn alloy sprayed coating comprising Sn in a
content of more than 1% by mass and less than 50% by mass
and a balance composed of Zn and a Zn-Sn-Mg alloy sprayed
coating comprising Sn in a content of more than 1% by
mass and less than 50% by mass, Mg in a content of more
than 0.01% by mass and less than 5% by mass and a balance
composed of Zn.
2. The pipe provided with a corrosion prevention layer
on the outside surface thereof, according to claim 1,
wherein:
the alloy sprayed coating of the corrosion prevention
layer comprises at least any one of Ti, Co, Ni and P; and
a content of each of Ti, Co, Ni and P is more than
0.001% by mass and less than 3% by mass.
3. A process for production of a pipe provided with a
corrosion prevention layer on an outside surface thereof,
wherein the process comprising, when the pipe provided
with a corrosion prevention layer on the outside surface
thereof according to claim 1 is produced,
heat treating the alloy sprayed coating at a
temperature equal to or higher than a eutectic
temperature of the alloy and lower than the melting point
of the alloy.
4. A process for production of a pipe provided with a
corrosion prevention layer on the outside surface thereof,
wherein the process comprising, when the pipe provided
with a corrosion prevention layer on the outside surface
thereof according to claim 1 is produced:

using one of a Zn-Sn wire, a Zn-Sn-Mg wire and a wire
produced by comprising at least any one of Ti, Co, Ni and
P in one of a Zn-Sn wire and a Zn-Sn-Mg wire as a first
wire and a Zn wire as a second wire; and
simultaneously arc spraying the first wire and the
second wire.
5. A process for production of a Zn-Sn-Mg alloy wire,
wherein the process comprising:
melting a material comprising Sn in a content of more
than 1% by mass and less than 50% by mass, Mg in a
content of more than 0.01% by mass and less than 5% by
mass and a balance composed of Zn; and
cooling a molten alloy under solidification, obtained
by the melting, at a cooling rate of 20°C/sec or more from
a temperature equal to or higher than the eutectic
temperature of a Zn-Sn-Mg alloy down to a temperature of
50°C or lower while the molten alloy is being solidified
so as to yield a wire rod type cast product with a
continuous casting machine.
6. The process for production of a Zn-Sn-Mg alloy wire
according to claim 5, wherein cooling water is sprayed
onto the molten alloy under solidification so as to yield
a wire rod type cast product.
7. A Zn-Sn alloy for spraying comprising Sn in a content
of more than 1% by mass and less than 50% by mass and a
balance composed of Zn.
8. The Zn-Sn alloy for spraying according to claim 7,
said alloy further comprising at least any one of Ti, Co,
Ni and P, wherein a content of each of Ti, Co, Ni and P
is more than 0.001% by mass and less than 3% by mass.
9. A Zn-Sn-Mg alloy for spraying comprising Sn in a
content of more than 1% by mass and less than 50% by mass,
Mg in a content of more than 0.01% by mass and less than
5% by mass and a balance composed of Zn.

10. The Zn-Sn-Mg alloy for spraying according to claim 9,
said alloy further comprising at least any one of Ti, Co,
Ni and P, wherein a content of each of Ti, Co, Ni and P
is more than 0.001% by mass and less than 3% by mass.
11. An alloy wire composed of the Zn-Sn alloy for
spraying according to any one of claims 7 and 8 or the
Zn-Sn-Mg alloy for spraying according to any one of
claims 9 and 10.

Disclosed is a pipe made of an iron-base material,
having a corrosion prevention layer formed on the surface
thereof. The corrosion prevention layer includes a Zn-Sn
sprayed coating including Sn in a content of more than 1%
by mass and less than 50% by mass and the balance
composed of Zn. Alternatively, the corrosion prevention
layer includes a Zn-Sn-Mg sprayed coating including Sn in
a content of more than 1% by mass and less than 50% by
mass, Mg in a content of more than 0.01% by mass and less
than 5% by mass and the balance composed of Zn.
Preferably, the sprayed coating of the corrosion
prevention layer includes at least any one of Ti, Co, Ni
and P, and the content of each of these elements is more
than 0.001% by mass and less than 3% by mass.