JPH0571666B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a protective film on a black galvanized steel sheet, and more specifically, after blackening a zinc alloy coated steel sheet, The present invention also relates to a method for producing a protective film on a black galvanized steel sheet, which forms a protective film with excellent corrosion resistance. [Prior art] Blackened steel sheets with improved decoration, light absorption, heat absorption, or light antireflection properties have been widely used for chassis of home appliances and peripheral parts of optical systems of copiers. . However, in recent years, for the purpose of cost reduction, the conventional blackening method of painting after processing is being replaced by a method of processing and using a zinc alloy plated steel sheet that has been blackened in advance. In the case where the steel sheet is blackened in advance in this manner, processing is performed after blackening, and therefore, such a steel sheet is required to have excellent workability. Further, the blackened and glazed steel sheet itself has poor wear resistance and is very easily damaged, so that the aesthetic appearance of the blackened coating is likely to be significantly impaired. Then, rust develops from the scratched part, and when it rusts, a white corrosion product is produced, which spoils the fine and beautiful appearance. As a blackened zinc alloy coated steel sheet on which a film is formed, one in which the surface is subjected to anodic electrolytic treatment is known (Japanese Patent Application Laid-open No. 154190/1983). [Problems to be solved by the invention] (Problems to be solved by the first invention and the second invention) Even with the technology disclosed in JP-A-58-151490, wear resistance cannot be sufficiently improved. However, the problem of rusting occurring and impairing the fine appearance as described in the prior art remains unsolved. In addition, the blackened layer on the surface of blackened zinc alloy coated steel sheets is more easily damaged during processing, and when the corrosion resistance is examined by a salt spray test (JIS2371) after processing, white rust occurs and the dense blackened surface is damaged. It gets lost. (Problems to be solved by the second invention) Although the above problems are solved by the first invention,
The steel sheet according to the first invention does not pay attention to the gloss of the black surface, and can be used for applications that are not strictly limited by gloss, such as decoration, but cannot be used for preventing light reflection. Can not. [Technical means for solving the problem] (First invention) The first invention according to the present application is directed to
A steel plate having a single layer or two or more plating layers of a zinc alloy mainly composed of zinc containing 0.5 to 30 wt% of Ni and Co and 0.5 to 10 wt% of Mo is treated with hydrochloric acid, sulfuric acid, and organic acids. A blackening treatment is carried out using a blackening treatment liquid containing one or more kinds in total of 0.1 to 20 wt% and a hydrogen peroxide solution of 0.1 to 20 wt%, and then on the surface of the blackened steel plate, Chromic anhydride at a ratio of 1 to the total solution
This is a method for producing a protective coating for a black galvanized steel sheet, which is characterized by forming a single layer or two or more layers of coating by coating and drying a solution containing an aqueous resin containing 200 g/g/g/~200 g/g/g/g/~200 g/g/g/g/g/g/g/g/~200 g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/- of a solution containing an aqueous resin, which is dried to form a single layer or two or more layers. (Second invention) The second invention according to the present application is one of Ni, Co or Mo.
A steel plate having a single layer or two or more plating layers of a zinc alloy mainly composed of zinc containing 0.5 to 30 wt% of Ni and Co and 0.5 to 10 wt% of Mo is treated with hydrochloric acid, sulfuric acid, and organic acids. The surface of the blackened steel plate is treated with a blackening treatment solution containing 0.1 to 20 wt% of one or more types in total and 0.1 to 20 wt% of hydrogen peroxide solution, and
Chromic acid reduced from 5 to 95 wt% of the total chromic acid is converted to chromic anhydride, and the ratio to the total solution is 1 to 95 wt%.
This is a method for producing a protective film for a black galvanized steel sheet, which is characterized by coating and drying an aqueous resin solution containing 200 g/ml to form a single layer or two or more layers. The total concentration of one or more types of hydrochloric acid, sulfuric acid, and organic acids (carboxylic acids) is 0.1 to 20wt.
% because if it is less than 0.1wt%, blackening will not occur within an appropriate processing time (within 2 to 3 minutes), and if it exceeds 20wt%, the blackening reaction will become faster and the reaction will not be able to be controlled. It is from. On the other hand, in the present invention, a hydrogen peroxide solution is used in addition to one or more of hydrochloric acid, sulfuric acid, and organic acids (carboxylic acids). The concentration of hydrogen peroxide solution is 0.1 to 20 wt%.
If the amount is less than 0.1 wt%, blackening will not occur within an appropriate processing time (within 2 to 3 minutes). Moreover, if the amount exceeds 20 wt%, the blackening reaction becomes faster and the reaction cannot be controlled. In this way, when hydrogen peroxide is used in addition to one or more of hydrochloric acid, sulfuric acid, and organic acids (carboxylic acids), it is possible to rapidly advance the blackening reaction without impairing corrosion resistance. Become.
In other words, when an acid such as sulfuric acid is used alone, it has both the action of an acid and the action of an oxidizing agent, so it tends to dissolve the galvanized layer, and in severe cases, it can expose the underlying iron. This can easily lead to deterioration of corrosion resistance. However, hydrochloric acid, sulfuric acid, organic acids (carboxylic acids)
When hydrogen peroxide is used in addition to one or more of the following at a predetermined concentration, each can be controlled independently and the blackening reaction can be carried out without dissolving the galvanized layer. can be accelerated. Note that the blackening treatment may be performed by, for example, dipping, spraying, or the like. In the first invention, a solution containing chromic anhydride is applied and dried. On the other hand, in the second invention, a solution containing partially reduced chromic acid is applied and dried. The components and composition of the chromic acid-containing aqueous resin used in the highly corrosion-resistant blackened zinc alloy coated steel sheet according to the present invention will be explained. The reason for including chromic acid in this way is as follows. In other words, when using water-based resin alone, the film thickness is 0.1 to 20
g/m ² , many pinholes may occur, and in salt spray tests etc., corrosion may progress from the pinholes and white rust may occur. Since the resin itself is not altered by salt water, corrosion only occurs from pinholes. When a water-based resin containing chromic anhydride is applied to a blackened zinc alloy plated steel sheet, the chromium compound coexists in the resin, and the self-healing action of the chromium compound suppresses the progress of corrosion from pinholes and prevents white rust. prevents the occurrence of corrosion and achieves high corrosion resistance. Here, the aqueous resin is a resin dispersed in water to form an emulsion. Aqueous resins that can be used in the present invention include:
Emulsion type that is stable even under strong acidic conditions.
3 types: water-soluble type and dispersion type that does not contain emulsifiers
type of resin can be used. Acrylic, epoxy, acrylic/styrene, and alkite resins can be used, and the composition range is solid content 1g/~400
g/ is preferred. If it is less than 1 g/l, the film forming properties are poor and the chromium compound cannot be bound, and if it is less than 400 g/l, the viscosity becomes extremely high, making it difficult to handle in practice. Preferably 10g/~300g/. In the first invention, chromic anhydride is contained in a proportion of 1 g/-200 g/to the total solution. On the other hand, in the second invention, the total chromic acid is
Chromic acid reduced to 95 wt% is contained in an amount of 1 to 200 g in terms of chromic anhydride. If the amount is less than 1 g, there is no effect of adding the chromium compound, and if it exceeds 200 g, it will be harmful to the degree of blackening of the black galvanized steel sheet. Preferably 1g/~
The concentration range is 100g/. Furthermore, the reduction rate of chromic anhydride used to control the gloss of black steel sheets is 5wt% to 95wt%.
If it is less than 5 wt%, it will have little effect on gloss, and if it exceeds 95 wt%, the amount of hexavalent chromium will decrease, self-healing action will decrease, and corrosion resistance will deteriorate. Preferably, the reduction rate is 10 wt% to 80 wt%. As in the second invention, when a solution containing an aqueous resin containing partially reduced chromic acid is applied and dried, a state in which chromium hydroxide or hydrate is dispersed in the aqueous resin is formed; Changes the light reflectance of the steel sheet surface and reduces gloss. Moreover, because some of it is reduced to trivalent chromium,
Due to the presence of chromium (trivalent) hydroxide and hydrate, the binding force to the steel plate surface increases and high corrosion resistance can be achieved because the surface is made more water-repellent. In addition, the coating amount of the coating in the first invention and the second invention is preferably in the range of 0.1 to 20 g/m ² . In addition, the blackening layer is treated with a blackening treatment liquid containing a total of 0.1 to 20 wt% of one or more of hydrochloric acid, sulfuric acid, and organic acids and 0.1 to 20 wt% of hydrogen peroxide. Although the adhesion of the above-mentioned film has not been elucidated to date, it has been confirmed that the adhesion is good, as it has been confirmed that it has excellent corrosion resistance as a result of the corrosion resistance test in the example described below. . [Example of the invention] (Example of the first invention) Example 11 Zn-Ni alloy plating (Ni content 12 wt%)
A ^blackening treatment was carried out by spraying a mixed aqueous solution of an acid and an oxidizing agent (hydrogen peroxide (5 wt%) and citric acid (5 wt%)) using a spray atomizer to the steel plate that had been subjected to the g/m 2 coating. After blackening treatment, a mixed coating solution containing water-based acrylic emulsion type resin (A) at a solid content concentration of 100 g/100 g/chromic acid anhydride and chromic acid anhydride at a chromic acid concentration of 10 g/100 g/ml was applied, followed by roll squeezing. and dried. The amount of film deposited was 3 g/m ² . (Example of the second invention) Example 21 After blackening the zinc-nickel alloy plating in the same manner as in Example 11, it contained an aqueous acrylic emulsion type resin (A) at a solid content concentration of 100 g/,
Further, a treatment solution containing 40% reduced chromic acid at a concentration of 10 g/m 2 was applied to a thickness of 2 g/m ² and dried. Example 22 After blackening the zinc-nickel alloy plating in the same manner as in Example 11, 25 g/50 g of water-based acrylic emulsion type resin (A) and 40% reduced chromic acid were added, respectively. A treatment solution containing a concentration of / was applied to a thickness of 2 g/ and dried. Example 23 After blackening the zinc-nickel alloy plating in the same manner as in Example 11, aqueous acrylic emulsion type resin (A) and 40% reduced chromic acid were added at 100 g/1 g, respectively. A treatment solution containing a concentration of / was applied to a thickness of 2 g/m ² and dried. Example 24 After blackening the zinc-nickel alloy plating in the same manner as in Example 11, aqueous acrylic emulsion type resin (A) and chromic anhydride were mixed at concentrations of 100g/10g/ and 10g//, respectively. The solution was applied to a coating thickness of 2 g/m ² and dried. Comparative Example 1 The zinc-nickel alloy plating was treated to blacken in the same manner as in Example 11. No protective film was applied (no treatment). Comparative Example 2 In the same manner as in Example 11, the zinc-nickel alloy plating was subjected to blackening treatment. A liquid mixture of water glass (JISI No. 3) and colloidal silica (20 wt%) at a ratio of 2:8 was applied and dried at a coating weight of 5 g/m ² . Comparative Example 3 The zinc-nickel alloy plating was treated to blacken in the same manner as in Example 11. Aqueous acrylic emulsion alone was applied to a film thickness of 5 g/m ² and dried. (Various Tests) The following tests were conducted on the black galvanized steel sheet on which the film was formed as described above. Blackness Blackness was measured using a color difference meter (manufactured by Suga Test Instruments Co., Ltd.). The smaller the L value, the better the blackness. Uniformity of appearance Uniformity of appearance was visually observed. Corrosion Resistance Corrosion resistance was tested in 5% salt water based on the salt spray test (JIS2371), and the time until white rust appeared was measured. Blackness after processing A bending process of 90° was performed, and the change in blackness after processing was visually measured. Glossiness Measured using a gloss meter (manufactured by Suga Test Instruments). The incident angle is 60°, and the amount of specular reflection for the 60° incident ray is expressed as a percentage of that of the reference surface Gs (60°)
I judged it. The above results are summarized in Table 1. As shown in Table 1, the degree of blackness before processing in the examples is comparable to that in the comparative examples. However, in the examples, the degree of blackness after processing, uniformity of appearance,
Corrosion resistance is superior to that of the comparative examples. Particularly in Examples 21 to 24, the uniformity of appearance is extremely excellent. [Effect of the invention] According to the first invention and the second invention according to the present application,
It is possible to obtain a black galvanized steel sheet that has excellent abrasion resistance, does not impair the aesthetic appearance of the blackened coating, does not rust, and does not impair its dense and beautiful appearance. According to the second aspect of the present application, subtle unevenness in dark tone that occurs on the surface due to the blackening treatment disappears, and a uniform surface tone can be obtained. That is, a transparent or transparent layer is coated on the blackening layer, changing the refractive index of light and improving the uniformity of the black surface. 【table】

Claims (1)

[Claims] 1. A single layer or a plated layer of a zinc alloy mainly composed of zinc containing one or more of Ni, Co, or Mo in an amount of 0.5 to 30 wt% for Ni and Co, and 0.5 to 10 wt% for Mo. A steel plate with two or more layers is treated with one or more types of hydrochloric acid, sulfuric acid, and organic acids in a total of 0.1 to 20 wt%.
and blackening treatment with a blackening treatment solution containing 0.1 to 20 wt% hydrogen peroxide solution, and then
A solution containing an aqueous resin containing chromic anhydride at a ratio of 1 g/~200 g/total solution is applied to the surface of the blackened steel sheet and dried to form a single layer or two or more layers. A distinctive method for producing a protective film on black galvanized steel sheets. 2 A steel sheet having a single layer or two or more plating layers of a zinc alloy whose main component is zinc containing one or more of Ni, Co, or Mo, 0.5 to 30 wt% for Ni and Co, and 0.5 to 10 wt% for Mo. , hydrochloric acid, sulfuric acid, one or more organic acids in total of 0.1 to 20wt%
and 0.1 to 20 wt% of hydrogen peroxide solution to blacken the surface of the blackened steel sheet.
An aqueous resin solution containing 1 to 200 g of chromic acid reduced to chromic anhydride based on the total solution is coated and dried to form a single or double layer film.
A method for producing a protective film on a black galvanized steel sheet, characterized by forming more than one layer.