JP2968147B2 - Acid displacement plating solution composition for zinc-containing metal plated steel sheet - Google Patents

Abstract

An acidic substitutional plating bath for zinciferous surfaces, particularly zinciferous metal-plated steel sheet, with which sludge production and equipment corrosion are inhibited and which has an improved heavy metal ion deposition efficiency is provided by an aqueous composition that has a pH of 2 to 4.5 and that contains 1.5 to 40 g/L of at least one heavy metal ion selected from nickel, iron, and cobalt; 0.5 to 10 g/L of phosphate ions; 1 to 250 g/L of sulfate ion; and 1 to 20 g/L of organic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acidic displacement plating solution composition for a zinc-containing metal-plated steel sheet. More specifically, the present invention can form a heavy metal coating for a coating base having extremely excellent coating film adhesion on the surface of the galvanized steel sheet by contacting the surface of the zinc-containing metal-plated steel sheet, The present invention also relates to an acidic displacement plating solution composition that can improve the black rust resistance of an uncoated plate and can maintain its initial performance for a long time and can be used continuously.

[0002] In the present specification, a zinc-containing metal-coated steel sheet includes a zinc-coated steel sheet and a zinc alloy-plated steel sheet. The zinc alloy includes, for example, a zinc-aluminum alloy, a zinc-nickel alloy, a zinc-iron alloy, and the like.

[0003]

2. Description of the Related Art Conventionally, zinc-containing metal-plated steel sheets have been
A method of treating with an aqueous acidic solution, particularly a phosphate aqueous solution, to form a coating undercoat film, and thereby improving the adhesion with a coating material applied thereon or other dry coating films has been widely and industrially implemented. ing. If the phosphate coating is controlled to have the proper coating amount and crystal size, the coating formed thereon will exhibit satisfactory coating performance. Therefore, it is necessary to control these physical quantities within an appropriate range.To that end, it is necessary to not only change the chemical conversion conditions in accordance with the type of plating on the steel sheet and the line speed of the steel sheet, but also to use It is necessary to frequently remove sludge generated in the wastewater.

[0004] In a low-lead hot-dip galvanized steel sheet in which the lead content in the galvanized layer is lower than that of a conventional hot-dip galvanized steel sheet, the grain boundaries in the galvanized layer and the interface between the galvanized layer and the alloy layer are reduced. Lead segregation was avoided and this was found to be effective in preventing corrosion. Therefore, low-lead hot-dip galvanized steel sheets are widely used in various industries. However, unlike the conventional hot-dip galvanized steel sheet, cracks are unlikely to occur at the time of bending, so that shear stress concentrates on the phosphate film located between the steel sheet and the coating film. For this reason, there is a problem that cohesive failure of the phosphate coating occurs, and as a result, the coating easily peels off.

In order to avoid the above problems, a coating type chromate treatment containing hexavalent chromium and trivalent chromium has been adopted as a coating base treatment instead of the phosphate treatment. This method is easy to maintain and control the composition of the processing solution,
In addition, it has the advantages that it can follow a variety of plating types and changes in line speed, and that there is less pollution problem of the processing waste liquid. However, the adhesion of the chromate film to the coating film is inferior to that of the phosphate film.

[0006] In order to improve the adhesion of the coating by improving the drawback that the coating type chromate coating tends to peel off, Japanese Patent Publication Nos. 43-12974, 52-22618 and 52-21818, In JP-A-52-43171 and JP-A-61-69978, etc., before subjecting a zinc-containing metal-plated steel sheet to a chromate treatment, the steel sheet is previously subjected to heavy metal displacement plating treatment with Ni, Co, and / or Fe or the like. Thereby, a method for improving coating film adhesion has been proposed.

[0007] Of these conventional methods, Japanese Patent Publication No. Sho 4
The disclosure of Japanese Patent Application Laid-Open No. 3-12974 discloses that a zinc-containing metal-plated steel sheet is treated with a basic aqueous solution containing Co ²⁺ , Fe ²⁺ , Fe ³⁺ , and Ni ²⁺ having a pH of 11 or more prior to chromate treatment. This method involves the problem that zinc ions elute and accumulate in the processing solution with the lapse of processing time, thereby producing a large amount of sludge.Therefore, it is necessary to remove this sludge. Occurs,
There was a problem in workability.

Further, Japanese Patent Publication No. 52-22618 and Japanese Patent Publication No. 52-43171 disclose prior arts such as Ni ²⁺ , Co having a pH of about 1.5 prior to chromate treatment.
^The present invention relates to a method of treating a galvanized steel sheet with an acidic solution containing ²⁺ , Fe ²⁺ , and / or Fe ^3+. However, each of these methods uses a highly corrosive hydrochloric acid as an inorganic acid. Therefore, unless a stainless steel container or piping coated with a rubber lining or the like is used, it is difficult to put these methods into practical use, and there is a problem that the working environment is deteriorated.

Further, the disclosure of Japanese Patent Application Laid-Open No. 61-69978 discloses that prior to the chromate treatment, a low-lead hot-dip galvanized steel sheet is treated with an aqueous solution of hydrochloric acid, sulfuric acid, or phosphoric acid containing Fe, Co, and / or Ni. Is related to the method of treating with any of the alkaline aqueous solution, of which,
When an aqueous solution of hydrochloric acid, sulfuric acid or an aqueous alkali solution is used, there is a problem that the precipitation of these metals becomes difficult due to an increase in zinc ions and an increase in pH with the lapse of the treatment time. On the other hand, when phosphoric acid is used, as described later, its pH buffering ability prevents the pH from rising, and the Fe, N
It is thought that the substitutional precipitation of i and / or Co is performed smoothly, but no description is found in the specification of the above-mentioned publication.

On the other hand, conventionally, a zinc-containing metal-plated steel sheet has been subjected to a chromate treatment for the purpose of improving corrosion resistance. This treatment has a remarkable effect in preventing the generation of white rust, but has a problem that black rust (called a blackening phenomenon) occurs during the stock period or during transportation. As a countermeasure against the black rust problem after such a chromate treatment, for example, as described in Japanese Patent Publication No. 3-49982, flash treatment with Ni, Co, Fe or the like is known. The above-mentioned Japanese Patent Publication 3-49982
The technology described in the publication includes Ni ²⁺ or Co ²⁺ ions prior to chromate treatment, and contains 1 to 4, or 11
By treating a zinc-containing metal-plated steel sheet with a treatment liquid having a pH of 13.5, black rust can be prevented. However, even with this method, when the zinc ion concentration increases with the treatment, there is a problem that sludge is generated and workability is reduced.

[0011]

If the surface of a galvanized steel sheet is subjected to a displacement plating treatment with Ni, Co, and / or Fe prior to the above-described chromate treatment according to the prior art, the adhesion of the coating film is reduced. This can be a powerful measure to eliminate the problem of defects and to improve the black rust resistance of unpainted plates. Therefore, the present invention, for zinc-containing metal-plated steel sheet, even if the zinc ion concentration in the replacement plating solution has increased after the treatment time, without generating sludge,
An object of the present invention is to provide a highly versatile acid-substituted plating solution composition for zinc-containing metal-plated steel sheets, in which heavy metals such as Ni, Co, and / or Fe are efficiently precipitated and corrosion of the apparatus hardly occurs. It is.

[0012]

Means for Solving the Problems Accordingly, the present inventors have:
In the acidic displacement plating solution disclosed in JP-B-52-22618 and JP-B-52-43171, attention is paid to the use of the property that sludge is not generated and its initial performance can be maintained for a long period of time. did. Furthermore, these prior art acidic displacement plating solutions are:
As described above, hydrochloric acid having a high corrosiveness is contained, so that it is necessary to improve this to reduce the corrosiveness of the container or the piping. Therefore, as a result of diligent research, instead of hydrochloric acid, phosphoric acid having a buffering function of pH was used to lower the corrosiveness, the amount of components contributing to etching was limited, and the pH was 2 to 2.
By adjusting to 4.5, the initial effect was effectively maintained.

That is, the acidic displacement plating solution composition for a zinc-containing metal-plated steel sheet according to the present invention comprises at least one selected from nickel, iron, and cobalt at 1.5 to 40 g / l in terms of metal atoms. Heavy metal ions and
0.5 to 10 g / liter of phosphate ion and 1 to 25
It contains 0 g / l of sulfate ions and 1 to 20 g / l of an organic acid, and has a pH of 2.0 to 4.5.

[0014]

The acidic displacement plating solution disclosed in the above-mentioned JP-B-52-22618 and JP-B-52-43171 uses hydrochloric acid, sulfuric acid, hydrofluoric acid, hydrofluoric acid, etc. for the purpose of pH adjustment. Inorganic acid, or citric acid, acetic acid, and organic acids such as oxalic acid, and zinc ions eluted into the plating solution, form a salt with the inorganic acid, or the organic acid complexed zinc ions Dissolved.
In such an acidic displacement plating solution, the pH tends to increase due to an increase in the zinc ion concentration, and therefore, the displacement plating reaction decreases. As a result, in order to maintain the pH of the plating solution at a desired value, the amount of the inorganic acid added is increased, and for example, a plating solution tank or piping made of stainless steel is easily corroded.

If, in order to avoid such corrosion, phosphoric acid having a high pH buffering capacity is previously added to the acidic displacement plating solution instead of the above-mentioned inorganic acid, the zinc ion concentration increases. Even so, the present inventors have found that the pH fluctuation is reduced and the amount of free inorganic acid ions can be suppressed. As a result, the disadvantages of the conventional acid displacement plating solution were solved, and the acid displacement plating solution having almost no corrosiveness to the above-mentioned stainless steel container or piping was able to be obtained.

The acidic displacement plating solution disclosed in the above-mentioned conventional example contains a compound such as antimony or tin so that the displacement plating reaction does not decrease even when the amount of zinc ions increases. In the invention, in order to maintain the initial displacement plating reaction for a long time without containing these compounds, the content of phosphate ions, sulfate ions, and organic acid ions that contribute to etching in the acidic displacement plating solution is adjusted. , Limited to a specific range, and the pH is 2.0 to 4.5.
It has been found by the present inventors that by adjusting the amount of zinc ion, a large amount of zinc ions do not accumulate and the plating solution can be used continuously.

The acidic displacement plating solution of the present invention must contain the following components. First, it is necessary to contain one or more heavy metal ions of nickel, iron, and cobalt. However, in order to supply them to the plating solution, these sulfates, phosphates, carbonates, etc. It is desirable to use salts, oxides, hydroxides, or organic acid salts.
Nitrate is not preferable because it may form a phosphate film when dissolving zinc, and chloride is also not preferable since chloride ions may accumulate and cause corrosion of plating equipment when used for a long time. .

The amount of the heavy metal ions contained in the plating solution is 1.5 to 40 g / liter in terms of metal atoms. If it is less than 1.5 g / liter, the amount of deposited metal is insufficient, and the desired effect cannot be obtained. on the other hand,
If it exceeds 40 g / liter, the amount of deposited metal is saturated, and the economical loss due to the removal of the liquid increases.

It is preferable to use orthophosphoric acid as a source of phosphate ions used in the present invention. Phosphoric acid contained in the plating solution is 0.5-
10 g / liter. If it is less than 0.5 g / liter, the pH of the plating solution rises sharply, affecting the component balance. If it exceeds 10 g / liter, its pH buffering capacity becomes saturated, and the etching amount of zinc increases. Increases, and the deposition efficiency decreases.

In the present invention, the sulfate ions are supplied from sulfuric acid, and the content is gradually increased because the sulfate ions are replenished as the zinc ions increase in order to capture the zinc ions. Therefore, the sulfate ion concentration is determined by the amount of etching of zinc and the amount of carry-out of the plating solution, but is generally in the range of 1 to 250 g / liter. 1g /
If it is less than 1 liter, it is insufficient to capture the eluted zinc ions, and if it exceeds 250 g / liter, its effect is saturated and economically disadvantageous.

The organic acid used in the present invention is at least one selected from glycolic acid, lactic acid, malic acid, tartaric acid, citric acid, gluconic acid, and ascorbic acid. 20 g / liter. When the concentration of the organic acid is less than 1 g / liter, not only is it insufficient to capture the eluted zinc, but also the pH buffer capacity becomes insufficient, and if it exceeds 20 g / liter, the effect is saturated. At the same time, the deposition efficiency of heavy metals decreases.

The pH of the acidic displacement plating solution of the present invention having the above-described component composition is adjusted within the range of 2.0 to 4.5. In order to maintain the pH value within the above range, plating is performed. Hydrofluoric acid or silicon hydrofluoric acid may be further added to the liquid. When the pH value is low, it may be adjusted by adding zinc oxide or ammonia. pH range from 2.0 to
The reason for limiting to 4.5 is that if the pH value is less than 2, it means that an excessive amount of inorganic acid is contained, so that the zinc etching amount becomes excessive, and if the pH value becomes lower, the problem of equipment corrosion is caused. On the other hand, when the pH value exceeds 4.5, the displacement plating reactivity decreases when the amount of eluted zinc ions increases, which is not preferable.

In order to carry out acid displacement plating, the surface of a zinc-containing metal-plated steel sheet is brought into contact with an acid displacement plating solution by spraying, dipping, coating or the like to perform desired displacement plating.
Then, it may be washed with water and dried. The temperature of the plating solution is from room temperature
It is sufficient that the treatment time is less than 1 minute at 80 ° C., and the amount of heavy metal to be precipitated is 1 to 100 mg / m ^{2 in} the case of a coating base treatment.
The desired performance can be satisfied if it is in the range of 0.3 to 20 mg / m ^{2 in} the range of 0.3 to 20 mg / m ^{2 in} the case of black rust prevention by rust prevention chromate treatment. If the amount of heavy metal is less than the lower limit, the desired effect may not be obtained, and if it exceeds the upper limit, the effect is saturated and an economic loss is caused. In addition, it is enough to dry the film so that the water flies.
The range of 0-100 ° C is usual.

The displacement plating solution of the present invention is applied to the surface of pure zinc, hot-dip galvanized, hot-dip galvanized containing aluminum or iron as an alloy component, electroplated zinc or galvanized steel sheet. The zinc-containing metal-plated steel sheet subjected to the displacement plating is usually subjected to a coating-type chromate treatment for the purpose of improving corrosion resistance, followed by painting. On the surface of the zinc-containing metal-plated steel sheet surface-treated in such a process, a dense etching surface is provided, and an anchor effect to the coating film thereby, and some sort of difference between the deposited heavy metal and the post-treatment chromate film. It is considered that the interaction effect (interaction) acts, and the adhesion between the zinc-containing metal-plated steel substrate and the coating film is improved by the effect that the chromate film is adsorbed and fixed to the surface of the plated steel plate. On the other hand, when the zinc-containing metal-plated steel sheet subjected to the displacement plating is subjected to the chromate treatment, the deposited Co, Ni, Fe, etc. act as a barrier against the oxidation reaction, and the growth of the oxide film on the plating layer immediately below, ie, It is considered that black rust is suppressed.

[0025]

The present invention will be described in more detail with reference to the following examples. It should be noted that these examples are described for explaining the present invention, and do not limit the present invention in any way.

Examples 1 to 3 and Comparative Examples 1 to 4 In each of Examples 1 to 3 and Comparative Examples 1 to 3, the composition shown in Table 1 was added to the test plate described in (1) below. Was subjected to displacement plating. Next, the test plate after the displacement plating treatment and the test test plate not subjected to the displacement plating treatment (Comparative Example 4) were subjected to washing, drying, chromate treatment described in the following (3) to (6), and The coating process was performed in this order. The test test plate subjected to the above treatment was subjected to the coated plate bending test and the coated plate corrosion resistance test described in (7) and (8) below. Table 2 shows the applied displacement plating conditions, the amount of zinc ions in the solution, the presence or absence of sludge, and the amount of heavy metal deposited by displacement plating for the treatment solution in which the test plate was continuously processed to dissolve zinc. ,
In addition, the results of the bending test of the coated plate and the corrosion resistance test of the coated plate are shown.

[0027]

[Table 1]

[0028]

[Table 2]

(1) Test specimen: hot-dip galvanized steel sheet,
Minimized spangled oil-free plate 0.35 mm thick, 90 g / m ² per unit area (2) Displacement plating treatment: as described in Table 1 (3) Washing: Spray washing with tap water for 10 seconds. (4) Drying: Drying was performed using a dryer.

(5) Chromate treatment: Coating type chromate liquid (Cr ⁶⁺ 4%, Cr ³⁺ 2%, SiO ₂ 9)
% Aqueous dispersion) was applied by a roll coating method at a target chromium adhesion amount of 60 mg / m ² , and then dried at a maximum temperature of 60 ° C. in a 150 ° C. hot air drying oven. (6) Coating: After coating the backside alkyd paint with a dry coating thickness of 6 μm by a bar coating method, it was baked and dried at a maximum temperature of 210 ° C. in a 300 ° C. hot air drying oven.

(7) Bending test of coated plate: JIS-G
According to the test method of the colored zinc-iron plate of −3312, each of the test plates was bent at 20 ° C. and the two inner spacing plates were used.
A T-bending test was performed, and the peeled state after the tape was peeled was evaluated according to the following criteria. 5: No abnormality 4: Crack only and peel area less than 5% 3: Peel area 5% to less than 25% 2: Peel area 25% to less than 50% 1: Peel area 50% or more

(8) Corrosion resistance test of coated plate: A 70 × 150 mm test plate was cut out from each test test plate and subjected to JIS-Z-
The salt spray test specified in 2371 was carried out, and the blisters generated on the surface of the coated plate after 500 hours were subjected to ASTM (Am
eric Society for Testin
g and Materials) standard.

Examples 4 to 6 and Comparative Examples 5 to 8 In each of Examples 4 to 6 and Comparative Examples 5 to 6, the test specimens described in (1) below were treated with the compositions shown in Table 3. Displacement plating was performed using the solution. Next, the test plate after the displacement plating treatment or the test test plate not subjected to the displacement plating treatment (Comparative Example 8) was subjected to washing, drying, chromate treatment, and painting described in the following (3) to (6). It was performed in this order. In addition, each of the test plates obtained by coating the test plate with zinc phosphate after the treatment in Comparative Example 7 was subjected to the bending test of the coated plate and the edge creep test of the coated plate described in (7) and (8) below. Provided. Table 4 shows the applied displacement plating conditions, the amount of zinc ions in the solution, the presence or absence of sludge, and the amount of heavy metal deposited by the displacement plating, for the treatment solution in which the test plate was continuously processed to dissolve zinc. ,
The results of the bending test of the coated plate and the edge creep test of the coated plate are shown.

[0034]

[Table 3]

[0035]

[Table 4]

(1) Test plate: extremely low-lead hot-dip galvanized steel plate (Pb content in plating bath 0.003%), oil-free plate, plate thickness 0.4 mm, basis weight 125 g / m ² (2 ) Displacement plating treatment: As described in Table 2 (3) Washing: Spray washing with tap water for 10 seconds. (4) Drying: Drying was performed using a dryer.

(5) Chromate treatment: Coating type chromate liquid (Cr ^{6+ .3} %, Cr ³⁺ .2%, SiO ₂ .7
%, Resin... 0.5%) is applied by roll coating at a target chromium deposition amount of 70 mg / m ² , and then heated to a maximum temperature of 60 ° C. in a hot air drying oven at 150 ° C. Dried.

(6) Coating: After coating an epoxy primer with a dry coating thickness of 5 μm by a bar coating method, baking and drying at a maximum temperature of 195 ° C. in a hot air drying furnace at 300 ° C., and then a polyester top coat. After coating with a dry film thickness of 12 μm, the maximum temperature of the plate reached 22 in a hot air drying oven at 300 ° C.
It was baked and dried at 0 ° C.

(7) Bending test of coated plate: JIS-G
In accordance with the test method of the colored zinc-iron sheet of −3312, each of the test specimens was bent at 20 ° C. and one of the inner spacing plates was used.
A T-bending test was performed, and the peeled state after the tape was peeled was evaluated according to the following criteria. 5: No abnormality 4: Crack only and peel area less than 5% 3: Peel area 5% to less than 25% 2: Peel area 25% to less than 50% 1: Peel area 50% or more

(8) Edge creep test of a coated plate: A 70 × 150 mm test plate was cut out from each test plate so that burrs appeared above and below both end faces, and a salt spray test specified in JIS-Z-2371. The maximum creep width (mm) from the end face after 1000 hours was measured on both sides, and the average value was described.

Examples 7 to 9 and Comparative Examples 9 to 11 In each of Examples 7 to 8 and Comparative Examples 9 to 10, the test specimens described in (1) below were treated with the compositions shown in Table 5. Displacement plating was performed using the solution. Next, the test plate after the displacement plating treatment or the test test plate not subjected to the displacement plating treatment (Comparative Example 11) is degreased, washed, dried, chromate-treated, and painted as described in the following (2) to (9). Were performed in this order. Then, the test test plate subjected to these treatments was subjected to the adhesion test of the coated plate and the corrosion resistance test of the coated plate described in (10) and (11) below. Table 6 shows the applied displacement plating conditions, the amount of zinc ions in the solution and the presence or absence of sludge, and the amount of heavy metal deposited by displacement plating for the treatment solution in which zinc was dissolved after continuous processing of the test plate. And the results of the adhesion test of the coated plate and the corrosion resistance test of the coated plate.

[0042]

[Table 5]

[0043]

[Table 6]

(1) Test specimen: electrogalvanized steel sheet,
Oiling plate, thickness 0.8 mm, basis weight 20g / m ^{2 (2)} Degreasing: Nihon Parkerizing Co. alkaline degreasing agent CL-N364S, temperature 60 ° C. with a 2% aqueous solution, was subjected spray 30 seconds. (3) Washing: Spray washing with tap water was performed for 10 seconds. (4) Roll drawing:

(5) Displacement plating treatment: As shown in Table 3 (6) Washing: Spray washing was performed with tap water for 10 seconds. (7) Drying: Drying was performed with a dryer.

(8) Chromate treatment: A coating type chromate solution (aqueous solution containing Cr ⁶⁺ ... 2% and Cr ^3+.
/ M ² , and then dried in a hot air drying oven at 250 ° C. at a maximum temperature of 150 ° C.

(9) Coating: After coating a baking type melamine alkyd paint with a dry coating thickness of 25 μm by a bar coating method,
It was baked and dried at a plate temperature of 140 ° C. for 20 minutes.

(10) Adhesion test of coated plate: Gobang test A square of 1 mm square was cut into each test test plate with a cutter so as to reach the base metal, and the degree of peeling of the coating film after tape peeling was observed. did. Erichsen test Each test plate was extruded by an Erichsen extruder by 6 mm, and the degree of peeling of the coating film after tape peeling was observed. The adhesion of the coated plate in the above items was evaluated in the following four stages according to the degree of peeling of the coating film. 4: Peeling of coating film 0% 3: Peeling of coating film less than 10% 2: Peeling of coating film 10% to less than 30% 1: Peeling of coating film 30% or more

(11) Corrosion resistance of the coated plate: A test plate of 70 to 150 mm was cut out from each test sample plate, a flaw reaching the base metal was cut into the coating film with a cutter, and a salt spray test was performed for 200 minutes.
After the time had elapsed, the tape was peeled off, and the maximum one-sided peeling width (mm) from the scratch was measured.

As is clear from Tables 1 and 2, in Comparative Example 1 in which no phosphate ion was contained in the displacement plating solution, the pH increased with an increase in the eluted zinc ion, so that the amount of heavy metal deposited was small. The bending adhesion of the painted plate decreased. In Comparative Examples 2 and 3, sludge was generated due to an increase in the amount of eluted zinc ions. Further, in Comparative Example 4, which was not subjected to the displacement plating, the adhesion of the coated plate was poor. However, in Examples 1 to 3 of the present invention, no sludge was generated even when the amount of eluted zinc ions increased, and the initial performance was maintained for a long period of time.

As is clear from Tables 3 and 4, in Comparative Examples 5 and 7, in which a zinc phosphate coating was formed on a very low lead galvanized steel sheet, the bent sheet adhesion of the coated sheet was poor. I was In Comparative Example 6 where the pH was low, the substitution precipitation of heavy metals decreased and sludge was generated as the amount of eluted zinc ions increased. Further, in Comparative Example 8, which was not subjected to the displacement plating treatment, the bent plate had poor adhesion and edge creep. However, in Examples 4 to 6 of the present invention, even when zinc ions eluted, a phosphate film was not formed, and the initial performance was maintained for a long time.

As is clear from Tables 5 and 6, in Comparative Example 9 in which no organic acid was added, the pH increased with an increase in the amount of eluted zinc ions, so that the amount of heavy metal deposited was reduced and the sludge was reduced. There has occurred. In Comparative Example 10 in which the concentration of heavy metal ions was low, the amount of heavy metal deposited decreased with an increase in the amount of zinc ions, and the adhesion of the coated plate decreased. Furthermore, in Comparative Example 11 in which the displacement plating was not performed, the adhesion and the corrosion resistance of the coated plate were inferior. However, in Examples 7 to 9 of the present invention, the initial performance was maintained for a long time, and the obtained coated plate also had excellent performance.

[0053] In each of Examples 10 to 12 and Comparative Examples 12 to 14 Examples 10 to 12 and Comparative Examples 12 to 14, the test test plate described in the following (1) composition shown in Table 7 Was subjected to displacement plating. next,
The test plate after the displacement plating treatment and the test test plate not subjected to the displacement plating treatment (Comparative Example 14) were subjected to washing, drying and chromate treatments described in the following (3) to (5) in this order. gave. The test plate subjected to the above treatment was subjected to a white rust acceleration test and a black rust acceleration test described in (6) and (7) below. Table 8 shows the applied displacement plating conditions, the amount of zinc ions in the solution, the presence or absence of sludge, and the amount of heavy metal deposited by the displacement plating for the treatment solution in which the test plate was continuously processed to dissolve zinc. , And the results of the white rust acceleration test and the black rust acceleration test are shown.

[0054]

[Table 7]

[0055]

[Table 8]

(1) Test specimen: Zinc-5% aluminum alloy-plated steel sheet 0.7 mm in thickness, 90 g / m ^{2 in} basis weight (2) Displacement plating treatment: as described in Table 7 (3) Cleaning: tap water Spray-washed with water for 10 seconds. (4) Drying: drying with a dryer.

(5) Chromate treatment: A coating type chromate solution (Cr ⁶⁺ ... 4%, Cr ³⁺ ... 2%) was applied by a roll coating method at a chromium adhesion amount of 25 mg / m ² ,
Drying was performed at a maximum temperature of 60 ° C. in a hot-air drying oven at 60 ° C.

(6) White rust accelerating test: 7
A test plate of 0 × 150 mm was cut out and subjected to JIS-Z-237.
The salt spray test specified in 1 was carried out, and the white rust generation area after 72 hours was visually determined according to the following criteria. 5: No white rust 4: White rust generation area less than 5% 3: White rust generation area: less than 5 to 25% 2: White rust generation area: 25 to less than 50% 1: White rust generation area: 50% or more

(7) Accelerated black rust test: 7
A plurality of test plates of 0 × 150 mm were cut out, the test surfaces of the test plates were faced to each other, and a pair was superimposed. After packing with vinyl-coated paper, four corners were tightened with bolts, and a torque wrench was used. After applying a load of 1 kg · f / cm ² for 240 hours in a wet tester at 49 ° C. and 98% relative humidity, the sample was taken out, and the blackening state of the overlapped portion was visually judged according to the following criteria. . 5: no blackening 4: extremely light gray 3: blackening less than 25% 2: blackening 25 to less than 50% 1: blackening 50% or more

As is clear from Tables 7 and 8, in Comparative Example 12 containing no phosphate ion and no organic acid, the initial heavy metal deposition amount was large and the white rust resistance was poor. After that, the pH decreases as the amount of eluted zinc ions increases,
The amount of heavy metal deposited was reduced, and black rust resistance was reduced. In Comparative Example 13, sludge was generated due to an increase in the amount of eluted zinc ions. Further, in Comparative Example 14 which was not subjected to the displacement plating treatment, the black rust resistance was poor.
However, in Examples 10 to 12 of the present invention, no sludge was generated even when the amount of eluted zinc ions increased, and the initial performance was maintained for a long period of time.

[0061]

The acid-substituted plating solution composition for zinc-containing metal-plated steel sheets according to the present invention, when used in a coating base treatment, can impart excellent adhesion and corrosion resistance to an excellent coated sheet. Also, when used for chromate substrate treatment, excellent black rust resistance can be imparted thereto, and the initial performance of the displacement plating solution can be maintained for a long time to enable continuous use. Its industrial value is great because it hardly corrodes.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-267279 (JP, A) JP-A-61-207580 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 18/00-18/54 C23C 22/78

Claims (3)

(57) [Claims] 1. At least one heavy metal ion selected from nickel, iron and cobalt in the amount of 1.5 to 40 g / l in terms of metal atom, and 0.5 to 10 g / l of the phosphate ion. Acid for zinc-containing metal-plated steel sheet, containing 1 to 250 g / l of sulfate ion and 1 to 20 g / l of organic acid, and having a pH of 2.0 to 4.5. Substitution plating solution composition. 2. The acidic displacement plating solution composition according to claim 1, wherein the organic acid comprises at least one of glycolic acid, lactic acid, malic acid, tartaric acid, citric acid, gluconic acid, and ascorbic acid. 3. The acidic displacement plating solution composition according to claim 1, wherein the pH is adjusted with at least one selected from hydrofluoric acid, hydrofluoric acid, zinc oxide, and ammonia. .