JPH083792A - Iron material for replenishing iron ion into iron-zinc alloy electroplating solution and method for replenishing iron ion and zinc ion - Google Patents

Abstract

PURPOSE:To obtain a high-quality iron-zinc alloy electroplating soln. by specifying the contents of C, Si, Mn, P, S, Cr and Al in am iron material for replenishing iron ion. CONSTITUTION:The iron material for replenishing iron ion has to contain, by weight, <=0.003% C, <=0.005% Si, <=0.05% Mn, <=0.002% P, <=0.003% S, <=0.003% Cu, <=0.01% Cr and <=0.003 Al. A plating soln. circulating tank 1, a metallic iron dissolving device 2 and a metallic zinc dissolving device 3 are connected in series through ducts 4a, 4b and 4c to circulate a plating sold., and the iron ion and zinc ion are replenished to the plating soln. Iron ion or zinc ion alone is repelenished, as required, by operating stop valves 12 and 13. The difference in solubility between metallic iron and metallic zinc and the fluctuations of iron content in the plating film can be coped with in this way.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention uses an iron-zinc alloy electroplating solution, an insoluble electrode, and supplying iron ions and zinc ions to the iron-zinc alloy electroplating solution. The present invention relates to an iron material for supplementing iron ions in an iron-zinc alloy plating solution and a method for supplementing iron ions and zinc ions when an iron-zinc alloy electroplating layer is formed on the surface of a steel strip.

[0002]

2. Description of the Related Art An iron-zinc alloy electroplating solution is used as a method for continuously forming an iron-zinc alloy electroplating layer on the surface of a cold-rolled steel sheet or a galvannealed steel sheet, and , While supplying iron ions and zinc ions to the iron-zinc alloy electroplating solution, a direct current is passed between the insoluble anode and the steel plate, thus continuously iron-zinc alloy electroplating on the surface of the steel plate. Methods of forming layers are known.

As a method of replenishing iron ions and zinc ions into the electroplating solution, for example, Japanese Patent Publication No. 60
The following method, as disclosed in Japanese Patent Publication No. -23200, Japanese Utility Model Laid-Open No. 58-148068, etc. (hereinafter referred to as Prior Art 1), is generally performed.

That is, as shown in the schematic system diagram of FIG. 2, a metal iron dissolving device 2'and a metal zinc dissolving device 3'are arranged in parallel with respect to the plating solution circulation tank 1 ', and the metal iron dissolving device 2 'Metallic iron filling inside, and metal zinc melting device
Fill 3'with zinc metal.

A plating solution circulating tank 1'and a metallic iron dissolving device 2 '
A conduit 4'through which the plating solution circulates is connected between the two. A pump 5'is provided in the middle of the conduit 4 ', and a filter 6'is provided on the outlet side of the metal iron dissolving device 2'of the conduit 4'and a branch pipe 7'that leads to the inlet side of the metal iron dissolving device 2'is provided. Connecting. Similarly, a conduit 4'through which the plating solution circulates is connected between the plating solution circulation tank 1'and the metal zinc dissolving device 3 '. conduit
A pump 5'is provided in the middle of 4 ', a filter 6'is provided on the outlet side of the metal zinc dissolving device 3'of the conduit 4', and a branch pipe 7'that connects to the inlet side of the metal zinc dissolving device 3'is connected. To do.

The electroplating solution introduced into the plating solution circulation tank 1'by a conduit 8'from an electroplating tank (not shown) is
Guided through a conduit 4'to each of a metal iron melting device 2'and a metal zinc melting device 3'connected in parallel to the circulation tank 1 ',
In the metallic iron melting device 2'and the metallic zinc melting device 3 ',
Metallic iron and metallic zinc are dissolved in the electroplating solution.
The plating solution in which metallic iron is dissolved and the plating solution in which metallic zinc is dissolved are respectively returned to the circulation tank 1'through the conduit 4 ', mixed in the circulation tank 1', and further passed through the conduit 9 '. It is delivered to the electroplating tank.

In this way, the plating solution from the electroplating tank is circulated through the circulation tank 1'and the metallic iron dissolving device 2'and the metallic zinc dissolving device 3 ', and the flow rate and the dissolving device 2',
By controlling the amounts of metallic iron and metallic zinc in 3 ', a predetermined amount of iron ions and zinc ions are replenished in the plating solution.

When the metallic iron and metallic zinc are dissolved in the electroplating solution by the above-mentioned method, metallic zinc having an extremely high purity (99.99% or more) can be obtained on an industrial scale. Regarding iron, it is extremely difficult to obtain high-purity metal such as metallic zinc, and even if it is available, it is expensive, so metallic iron containing impurities to some extent must be used.

Therefore, the electroplating solution in which metallic iron is dissolved in the metallic iron dissolving apparatus 2'contains a relatively high concentration of impurities, and the electroplating solution containing such impurities and the metal The electroplating solution in which metallic zinc is dissolved in the zinc dissolving device 3'is mixed in the circulation tank 1'and sent to the electroplating tank.

As a result, when the steel sheet is electroplated in the electroplating bath, iron-zinc having a desired component composition may be present on the steel sheet depending on the type and concentration of the above-mentioned impurities contained in the electroplating solution. It may be difficult to form the alloy electroplating film, and further, the adhesion of the plating film may be poor, the corrosion resistance may be deteriorated, and the plating appearance may be poor.

As a means for solving the above-mentioned problems, for example, in Japanese Patent Laid-Open No. 63-282297, an iron material for supplementing iron ions in which the content of a specific impurity component is limited is C: 0.05 w.
t.% or less, Si: 0.1 wt.% or less, Cu: 0.1 wt.% or less, Sb:
An iron material for replenishing iron ions in an iron-based plating solution (hereinafter referred to as Prior Art 2) is disclosed, which comprises 0.01 wt.% Or less, Sn: 0.01 wt.% Or less, and the balance Fe and impurities.

On the other hand, in JP-A-3-150400, a metallic iron dissolving device and a metallic zinc dissolving device are arranged in series, and an electroplating solution is introduced into a metallic iron dissolving device to dissolve metallic iron in the plating solution. Then, the plating solution in which the metallic iron is dissolved is guided to the metallic zinc dissolution device to dissolve the metallic zinc in the plating solution, and when the metallic zinc is dissolved, the impurities in the plating solution are deposited on the surface of the metallic zinc. A method (hereinafter referred to as prior art 3) is disclosed.

That is, as shown in the schematic system diagram of FIG. 3, a metallic iron dissolving device 2'and a metallic zinc dissolving device 3'are arranged in series with respect to a plating solution circulating tank 1 ', and the plating solution is placed in the tank. Connect the circulating conduit 4 '. A pump 5'is provided in the middle of the conduit 4 ', and a filter is provided in the conduit 4'on each outlet side of the metallic iron melting device 2'and the metallic zinc melting device 3'of the conduit 4'.
6'is provided and a conduit 4'on each outlet side of the filter 6'is connected to a branch pipe 7'which leads to each inlet side of the metal-iron dissolving device 2'and the metal-zinc dissolving device 3 '.

The electroplating solution introduced into the plating solution circulation tank 1'from an electroplating tank (not shown) by the conduit 8'is
First, metallic iron is dissolved in the plating solution in the metallic iron dissolving apparatus 2 ′ filled with metallic iron, and then metallic zinc is dissolved in the plating solution in the metallic zinc dissolving apparatus 3 ′. During the dissolution of the metallic zinc, impurity ions in the plating solution are deposited on the surface of the metallic zinc. As a result, the content of impurities in the plating solution is reduced, and a predetermined amount of iron ions and zinc ions are replenished in the plating solution.

[0015]

The prior art 2 has the following problems. That is, there are many kinds of impurities contained in metallic iron. Therefore, it is difficult to form an iron-zinc alloy electroplating film having a desired component composition on a steel plate due to a complex action of impurities not specified by Prior Art 2 and a plurality of kinds of impurities, It is not possible to sufficiently prevent poor adhesion of the plating film, deterioration of corrosion resistance, poor appearance of the plating, and the like.

Prior art 3 has the following problems.
That is, at the time of actual operation, due to the difference in the dissolution rate between metallic iron and metallic zinc, the fluctuation of the iron content in the plating film, etc., only iron ions or zinc ions are supplied to the plating bath alone. There may be a need. However, in the method of Prior Art 3, since the metal iron melting device and the metal zinc melting device are arranged in series, it is not possible to replenish each of the above-mentioned iron ions or zinc ions alone. Therefore, the method of Prior Art 3 is difficult to apply to actual operations.

Therefore, an object of the present invention is to solve the above-mentioned problems and to plate a metal iron dissolver and a metal zinc dissolver in order to continuously form an iron-zinc alloy electroplating layer on the surface of a steel sheet. By circulating the solution and dissolving metallic iron and metallic zinc in the plating solution, it is possible to obtain a high-quality iron-zinc alloy electroplating solution when replenishing iron ions and zinc ions in the plating solution. Moreover,
When there is a difference in the dissolution rate between metallic iron and metallic zinc, or when the iron content in the plating film fluctuates, it is possible to replenish the plating bath with iron ions or zinc ions alone. The present invention provides an iron material for supplying iron ions to an iron-zinc alloy electroplating solution suitable for actual operation, and a method for supplying iron ions and zinc ions.

[0018]

According to claim 1 of the present invention,
It is an invention that defines the component composition of an iron material for supplementing iron ions, wherein C, Si, Mn, P in the iron material for supplementing iron ion,
The content of S, Cu, Cr and Al is C: 0.003 wt.% Or less,
Si: 0.005 wt.% Or less, Mn: 0.05 wt.% Or less, P: 0.002
wt.% or less, S: 0.003 wt.% or less, Cu: 0.003 wt.% or less,
It is characterized by being limited to Cr: 0.01 wt.% Or less and Al: 0.003 wt.% Or less.

A second aspect of the present invention is an invention relating to a method for replenishing iron ions and zinc ions into an iron-zinc alloy electroplating solution, wherein the iron-zinc alloy electroplating solution from the electroplating tank is plated with a plating solution. It is led to a circulation tank, and the plating solution is filled with the plating solution circulation tank, a metallic iron dissolving device filled with metallic iron and a metallic zinc, which are connected in series by a circulation conduit. It is circulated between a metallic zinc dissolving device, and the metallic iron is dissolved in the plating solution by the metallic iron dissolving device, and then metallic zinc is dissolved by the metallic zinc dissolving device in the plating solution in which the metallic iron is dissolved. 2. The method for dissolving and thus replenishing iron ions and zinc ions in an iron-zinc alloy electroplating solution, wherein the metallic iron to be filled in the metallic iron dissolving device is the above-mentioned metallic iron. And an electroplating solution circulation tank, and each of the metal iron dissolving device and the metal zinc dissolving device are connected in parallel by separate conduits, and the circulation conduit is used. Further, by operating an on-off valve provided in the other conduit, only iron ions or zinc ions can be independently supplied to the electroplating solution.

[0020]

In the invention described in claim 1, the reason why the component composition of the iron material for supplementing iron ions is limited to the above range will be described below. When C exceeds 0.003 wt.% And / or Si exceeds 0.005 wt.%, C and / or Si dissolves during the dissolution, which remains as a floating substance in the plating solution and contaminates the plating solution. Therefore, the C content in the iron ion supplementary iron material should be limited to 0.003 wt.% Or less, and the Si content should be limited to 0.005 wt.% Or less.

At least one of Mn, P, S, Cu, Cr and Al has a content described below, that is, Mn: 0.05 wt.%,
P: 0.002 wt.%, S: 0.003 wt.%, Cu: 0.003 wt.%, C
If r: 0.01 wt.% and Al: 0.003 wt.% are exceeded, abnormalities will occur in the electrodeposition behavior and electrodeposited crystals, resulting in poor plating quality. Therefore, the Mn content is 0.05 wt.% Or less, and the P content is 0.
002 wt.% Or less, S content 0.003 wt.% Or less, Cu content
The Cr content should be limited to 0.003 wt.% Or less, the Cr content to 0.01 wt.% Or less, and the Al content to 0.003 wt.% Or less.

Next, the method according to claim 2 of the present invention,
Description will be given based on the schematic process diagram shown in FIG. As shown in FIG. 1, the plating solution circulating tank 1, the metallic iron dissolving device 2 and the metallic zinc dissolving device 3 are connected in series by a circulation conduit 4. A pump 5a is provided in the middle of the first conduit 4a connecting the plating solution circulation tank 1 and the metallic iron dissolving device 2.
Is provided, and in the middle of the second conduit 4b that connects the metallic iron dissolving device 2 and the metallic zinc dissolving device 3 and the third conduit 4c that connects the metallic zinc dissolving device 3 and the plating solution circulation tank 1, A filter 6 is provided for each.

The content of C, Si, Mn, P, S, Cu, Cr and Al described above as metallic iron for iron ion supplementation in the metallic iron melting apparatus 2 is C: 0.003 wt.%. Below, Si: 0.005 w
t.% or less, Mn: 0.05 wt.% or less, P: 0.002 wt.% or less,
S: 0.003 wt.% Or less, Cu: 0.003 wt.% Or less, Cr: 0.01 w
An iron material having a component composition limited to t.% or less and Al: 0.003 wt.% or less is filled. In addition, the metal zinc melting device 3
The inside is filled with metallic zinc for supplementing zinc ions.

A second conduit 4b connecting the metallic iron dissolving device 2 and the metallic zinc dissolving device 3 is connected with another conduit 10 branching from this to the plating solution circulating tank 1 and the plating solution circulating tank 1 And the metallic iron melting device 2 are the first conduit 4a,
It is also connected by the second conduit 4b and another conduit 10. On the other hand, the plating solution circulation tank 1 and the metal zinc dissolving device 3
Another conduit 11 is connected between the and, and the plating solution circulation tank 1 and the metallic zinc dissolving device 3 are also connected by the third conduit 4c and another conduit 11.

A first opening / closing valve 12 is provided in the middle of another conduit 10 branched from the second conduit 4b, and a second conduit between the branch point with the other conduit 10 and the metal-zinc melting device 3 is provided. A second opening / closing valve 13 is provided at 4b. A plating solution supply conduit 8 and a plating solution discharge conduit 9 are connected to the plating solution circulation tank 1.

During normal operation, the iron-zinc alloy electroplating solution introduced from the electroplating tank (not shown) into the plating solution circulating tank 1 by the plating solution supply conduit 8 is pumped by the pump 5a.
By the operation of, the metal iron dissolver 2 is fed through the first conduit 4a, then the metal zinc dissolver 3 through the second conduit 4b, and the plating is conducted through the third conduit 4c. Return to the liquid circulation tank 1. As described above, when the plating solution is circulating in the plating solution circulation tank 1, the metal iron dissolving device 2 and the metal zinc dissolving device 3, the first opening / closing valve 12 provided in the middle of another conduit 10 is closed. , The second provided in the second conduit 4b
The on-off valve 13 is open. At this time, the pump 5b provided in the middle of another conduit 11 that connects the plating solution circulation tank 1 and the metal zinc dissolving device 3 does not operate.

As a result, first, metallic iron is dissolved in the plating solution in the metallic iron dissolving device 2, and then metallic zinc is dissolved in the plating solution in which the metallic iron is dissolved in the metallic zinc dissolving device 3. Thus, the plating solution is sequentially circulated between the plating solution circulation tank 1, the metallic iron dissolving device 2 and the metallic zinc dissolving device 3, and the iron-zinc alloy electroplating solution is supplemented with iron ions and zinc ions.

When it is necessary to replenish the plating solution with iron ions alone due to a difference in dissolution rate between metallic iron and metallic zinc, a change in iron content in the plating film, and the like,
Open the first on-off valve 12 provided in the middle of another conduit 10,
The second on-off valve 13 provided in the second conduit 4b is closed. As a result, the plating solution in the plating solution circulation tank 1 is pumped by the pump 5a.
Is fed to the metallic iron dissolving device 2 through the first conduit 4a, and then returned to the plating solution circulating tank 1 through the second conduit 4b and another conduit 10. Thus, the plating solution circulates between the plating solution circulation tank 1 and the metallic iron dissolving device 2, and only iron ions are replenished in the iron-zinc alloy electroplating solution.

When it is necessary to replenish the plating solution with zinc ions alone, a separate conduit 11 for connecting the plating solution circulation tank 1 and the metallic zinc dissolving device 3 is provided. The pump 5b is operated. As a result, the plating solution in the plating solution circulation tank 1 is sent to the metal zinc dissolving device 3 through another conduit 11, and then the third conduit 4c.
And is returned to the plating solution circulating tank 1. Thus,
The plating solution circulates between the plating solution circulation tank 1 and the metallic zinc dissolving device, and only zinc ions are replenished in the iron-zinc alloy electroplating solution.

The iron material for replenishing iron ions filled in the metallic iron dissolving device 2 has the above-mentioned component composition, and the impurities thereof are limited to a very small amount over a wide range. Therefore, as in the conventional case, impurities remain in the plating solution and contaminate the plating solution, or the electrodeposition behavior due to impurities,
There is no problem that the plating quality is deteriorated due to the abnormality of the deposited crystal.

During normal operation, the metallic iron melting device 2
In the plating solution, metallic iron is dissolved, and then, in the metallic zinc dissolving device 3, metallic zinc is dissolved in the plating solution in which metallic iron is dissolved. Therefore, when the metallic zinc is dissolved, impurity ions in the plating solution are As a result of substitution and precipitation on the surface of metallic zinc, the content of impurities in the plating solution can be reduced.

In this way, the iron-zinc alloy electroplating solution, which is replenished with iron ions and zinc ions and has a low impurity content generated during iron ion replenishment, is used in the circulation tank 1.
From the above, it is fed to the electroplating tank (not shown) through the conduit 9.

The precipitation of the impurity ions during the dissolution of the metallic zinc described above also occurs in the case of the prior art 1 shown in FIG. 2, in which the metallic iron dissolving device and the metallic zinc dissolving device are connected in parallel to the plating solution circulation tank. , To some extent.
However, in the case of Prior Art 1, the impurities in metallic iron are not limited to a sufficiently low amount.

Further, in the case of the prior art 1, the metallic iron is dissolved in the metallic iron dissolving device 2'and the plating solution having a high impurity content is dissolved in the metallic zinc dissolving device 3 '. The plating solution is mixed with another plating solution in the plating solution circulation tank 1 ′, and the plating solution in which the content ratio of impurities is reduced to some extent by such mixing is circulated between the metal zinc dissolving device 3 ′. Therefore, the effect of removing impurities by the precipitation of impurity ions is extremely low.

On the other hand, according to the method of the present invention, the impurities in the iron material for replenishing iron ions filled in the metallic iron dissolving device 2 are limited to a very small amount over a wide range. In addition, since the plating solution containing an extremely small amount of impurities circulates between the plating solution and the metal zinc dissolving device, the efficiency of removing impurities by depositing impurity ions is extremely high.

The iron content and the zinc content in the plating solution are the amount of metallic iron in the metallic iron dissolving device 2, the amount of metallic zinc in the metallic zinc dissolving device 3, and the amount of metallic iron dissolving device and metal. Each of the zinc melting devices has a structure in which a plurality of small devices are connected in parallel, and can be controlled by changing the ratio of both by changing the operating number of each device.

[0037]

EXAMPLES Next, the present invention will be described based on examples in comparison with comparative examples. A cold-rolled steel strip having a thickness of 0.8 mm was subjected to an iron-zinc alloy electroplating treatment while supplying iron ions and zinc ions under the following conditions according to the process of the present invention shown in FIG. 1 to obtain a cold-rolled steel strip. An iron-zinc alloy electroplating film was formed on the surface of the
Nos. 1 to 3 were prepared.

[0038] (1) plating solution component composition _{FeS0 4 · 7H 2 O: 300} g / l ZnS0 4 · 7H 2 O: 150 g / l Na 2 S0 4: 50 g / l

(2) Plating solution temperature: 50 ° C. (3) Plating solution flow rate: 2 m / sec (4) Plating current density: 100 A / dm ² (5) Insoluble anode: Pt-Ir coated Ti electrode

(6) Supplemental metal zinc: high-purity granular zinc of 99.99% or more (particle size 2 to 3 mm) (7) Supplemental metal iron: C, Si, Mn, shown in Table 1
Cylindrical iron material (3 mm φ × 3 mm) having a composition that the content of P, S, Cu, Cr and Al is limited within the scope of the present invention

(8) Metallic iron dissolving device: a packed tower type with a diameter of 80 mm and a capacity of 4 liters, the plating solution is supplied from the lower part and discharged from the upper part. (9) Metallic zinc dissolving device: the same packed tower type as above
Diameter 80 mm, capacity 2 liters (10) Target plating amount: 40 g / m ² (11) Target iron content rate: 13 to 17 wt.%

When it is necessary to replenish the plating solution with iron ions alone due to a difference in dissolution rate between metallic iron and metallic zinc and a variation in iron content in the plating film,
By switching the first on-off valve 12 and the second on-off valve 13, the plating solution sent to the metal iron dissolving device is returned to the plating solution circulating tank and circulated between the plating solution circulating tank and the metal iron dissolving device. Then, only iron ions were replenished in the plating solution.

[Comparative Example 1] For a cold-rolled steel strip having a plate thickness of 0.8 mm, a prior art 1 in which a metal iron dissolving device and a metal zinc dissolving device were connected in parallel to a plating solution circulating tank shown in FIG. In the same manner as in the above-mentioned example, the iron-
Zinc alloy electroplating treatment was performed to form an iron-zinc alloy electroplating film on the surface of the cold rolled steel strip, and comparative specimens Nos. 1 to 3 were prepared.

[Comparative Example 2] C, Si, Mn, P, S, Cu, Cr were added as supplementary metallic iron to a cold-rolled steel strip having a plate thickness of 0.8 mm.
And an iron material in which at least one of Al content is out of the range of the present invention is used, and otherwise, the iron-zinc alloy electroplating treatment is performed under the same conditions as in the above-described example while supplying iron ions and zinc ions. Then, an iron-zinc alloy electroplating film was formed on the surface of the cold-rolled steel strip to prepare comparative specimens Nos. 4 to 6.

[Comparative Example 3] C, Si, Mn, P, S, Cu, Cr were added as supplementary metallic iron to a cold-rolled steel strip having a plate thickness of 0.8 mm.
And the same iron material as in Comparative Example 2 in which the content of at least one of Al and Al is out of the range of the present invention, and the metal iron dissolving device and the metal zinc dissolving device shown in FIG. According to the prior art 1 process connected in parallel, the iron-zinc alloy electroplating treatment was performed while supplementing the iron and zinc ions under the same conditions as in the above-described example, and iron-on the surface of the cold rolled steel strip. A zinc alloy electroplating film was formed to prepare comparative specimens Nos. 7-9.

Table 1 shows the component composition of the supplementary metallic iron used in the preparation of the test samples No. 1 to 3 of the present invention and the test samples No. 1 to 9 for comparison, and the plating adhesion amount and plating film of each test sample. The Fe content in the steel is shown.

[0047]

[Table 1]

Specimens of the present invention Nos. 1 to 3 and comparative specimens
For each of Nos. 1 to 9, the plating appearance, corrosion resistance, and adhesion of the plating film were examined and evaluated as described below.

(1) Plating appearance: The color tone and plating unevenness of the plating film were visually examined and evaluated as follows. ◯: Good, Δ: Slightly bad, X: Bad.

(2) Corrosion resistance: Full-dip type zinc phosphate treatment is applied to each of the present invention sample and the comparative sample to form a zinc phosphate coating, and then cationic type electrodeposition coating is performed. Apply and apply a thickness of 2 on the zinc phosphate coating.
A 0 μm coating was formed and then the coating was cross cut. For the specimens thus cross-cut, the swelling width of the coating film on the cross-cut portion of the specimens after 720 hours in the salt spray test specified in JIS Z2371 was measured, and by the swelling width, It evaluated as follows. ◯: Blistering width of 2 mm or less, Δ: Blistering width of more than 2 mm, 4 mm or less, ×: Blistering width of more than 4 mm.

(3) Adhesion of plating film: Each of the sample of the present invention and the sample for comparison was bent by an OT bending machine with its plated surface inside, and then opened, and then an adhesive tape was attached to the surface. Then, the adhesive tape was peeled off and evaluated according to the blackening degree of the adhesive tape as follows. ◯: Good, Δ: Slightly bad, X: Bad.

Table 1 also shows the evaluation results of the above-mentioned tests for the present invention specimens Nos. 1 to 3 and the comparative specimens Nos. 1 to 9.

As is clear from Table 1, the comparative sample N
o.1 to 3 are samples of the present invention No. 1 to 3 as supplementary metallic iron.
Although the same iron material having the same composition as that of C, Si, Mn, P, S, Cu, Cr, and Al within the scope of the present invention was used as shown in FIG. The appearance of the plating film was poor in both cases because the metal iron dissolving device and the metal zinc dissolving device were connected in parallel to the plating solution circulation tank, and thus the appearance of the plated coating was poor. The adhesion of the coating was also poor.

Comparative specimens Nos. 4 to 6 were replenished in accordance with the process of the present invention shown in FIG. 1, even though the iron-zinc alloy electroplating treatment was performed while replenishing iron ions and zinc ions. Comparative metal sample No.4
However, the appearance of the plating film was poor because an iron material containing a large amount of Si, P and Cr exceeding the range of the present invention was used. Further, in Comparative Sample No. 5, the appearance and adhesion of the plated coating were poor because an iron material containing a large amount of C, Si and Cr exceeding the range of the present invention was used. The comparative sample No. 6 used an iron material containing a large amount of C, Si, P and Cr, all exceeding the range of the present invention, so that the appearance of the plating film was extremely poor and the corrosion resistance and The adhesion was also poor.

The comparative specimens Nos. 7 to 9 used the same iron material as the comparative specimens Nos. 4 to 6 whose component composition was out of the range of the present invention as the supplementary metallic iron, and the plating was performed. Since the process of Prior Art 1 in which a metal iron dissolving device and a metal zinc dissolving device were connected in parallel to the liquid circulation tank was performed, the appearance, corrosion resistance and adhesion of the plated coating were all poor.

On the other hand, in the samples Nos. 1 to 3 of the present invention, as supplementary metallic iron, the contents of C, Si, Mn, P, S, Cu, Cr and Al are limited within the range of the present invention. Since the iron-zinc alloy electroplating treatment was performed by using the iron material having the different component composition and according to the process of the present invention shown in FIG. 1 while supplementing the iron ion and the zinc ion, the plating appearance, corrosion resistance and plating All of the adhesion of the coating was excellent.

Further, in the above embodiment, the Ni content of the supplemental metallic iron is 0.01 wt.% Or less, and the content of each of Pb, Sn, Cd, As and Sb is 0 or 0.0001 wt.%. It was as follows, and thereby, a more excellent effect was exhibited in improving the above-mentioned plating appearance, corrosion resistance and plating film adhesion.

As described above, according to the present invention,
In order to continuously form an iron-zinc alloy electroplating layer on the surface of a steel sheet, a plating solution is circulated through a metal iron dissolving device and a metal zinc dissolving device to dissolve metal iron and metal zinc in the plating liquid. This makes it possible to obtain a high-quality iron-zinc alloy electroplating solution when replenishing iron ions and zinc ions into the plating solution, and moreover, the difference in the dissolution rate between metallic iron and metallic zinc, and in the plating film. When a change in the iron content of, etc. occurs, it is possible to replenish the plating bath with iron ions or zinc ions alone.
It has industrially useful effects, such as being applied to actual operations and producing extremely excellent results.

[Brief description of drawings]

FIG. 1 is a schematic process diagram showing a method of the present invention.

FIG. 2 is a schematic process diagram showing a method of Prior Art 1.

FIG. 3 is a schematic process diagram showing a method of prior art 3.

[Explanation of symbols]

 1,1 'plating solution circulation tank, 2,2' metal iron dissolving device, 3,3 'metal zinc dissolving device, 4,4' circulation conduit, 4a first conduit, 4b second conduit, 4c third conduit, 5a, 5b, 5'pump, 6, 6'filter, 7'branch pipe, 8, 8'supply pipe, 9, 9'exhaust pipe, 10,11 separate conduit, 12 1st opening / closing valve, 13 2nd opening / closing valve.

Claims (2)

[Claims] 1. C, Si, Mn, in iron material for replenishing iron ions,
The contents of P, S, Cu, Cr and Al are C: 0.003 wt.% Or less, Si: 0.005 wt.% Or less, Mn: 0.05 wt.% Or less, P: 0.
An iron-zinc alloy characterized by being limited to 002 wt.% Or less, S: 0.003 wt.% Or less, Cu: 0.003 wt.% Or less, Cr: 0.01 wt.% Or less, and Al: 0.003 wt.% Or less. Iron material for replenishing iron ions in the electroplating solution. 2. An iron-zinc alloy electroplating solution from an electroplating tank is introduced into a plating solution circulating tank, and the plating solution is connected in series with the plating solution circulating tank by a circulation conduit. , Circulating between a metallic iron dissolving device filled with metallic iron and a metallic zinc dissolving device filled with metallic zinc, and dissolving metallic iron in the plating solution with the metallic iron dissolving device, and then, In the method of resolving iron zinc and zinc ions in the iron-zinc alloy electroplating solution, by dissolving the metal zinc in the plating solution in which the metal iron is dissolved in the metal zinc dissolving device, thus,
An iron material having the component composition according to claim 1 is used as the metallic iron to be charged into the metallic iron dissolving device, and the electroplating solution circulation tank, the metallic iron dissolving device and the metallic zinc dissolving device are used. Each of them is connected in parallel by another conduit, and iron ions alone or zinc ions alone are individually contained in the electroplating solution by the operation of the opening / closing valve provided in the circulation conduit and the other conduit. A method for replenishing iron ions and zinc ions into an iron-zinc alloy electroplating solution, which is characterized in that