JPS62270799A - Colored surface-treated steel sheet and its production - Google Patents

Abstract

PURPOSE:To produce the title steel sheet having excellent appearance, workability, and corrosion resistance by carrying out electrolysis with a plated steel sheet as the cathode in an aq. soln. at a specified pH contg. a water-soluble cationic polymer, a zinc ion, and a coloring ion. CONSTITUTION:Electrolysis is carried out with a plated steel sheet or a steel sheet as the cathode in an aq. soln. at >=1.5pH contg. a water-soluble cationic polymer, a zinc ion, and a metallic ion whose oxide is colored to form a composite coated film of >=0.1g/m<2>. A quaternary amine polymer can be effectively used as the cationic polymer, the mol.wt. is regulated to about 10<3>-10<6>, polyamide sulfone, etc., can be used, and the addition amt. is controlled to 15-20g/l. The zinc ion is added by 60-120g/l as the zinc sulfate. When Fe<2+> and Cr<3+> are compositely added as the coloring ions, black appearance can be easily obtained, and the concn. is preferably controlled to about 20-100g/l in the form of sulfate. After electrolysis, the sheet is washed with water, a guard coat (chromate coated film, etc.) is applied in <=about 1.5mu, hence the uniformity of the appearance is improved, and the degree of coloration is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a colored steel plate, particularly a black steel plate, used for members requiring decoration.

(Prior Art) The development of low-cost, high-performance surface-treated steel sheets has been consistently required in the fields of automobile anticorrosive steel sheets, household steel sheets, furniture, and building materials. These required standards are becoming lower and lower each year.
With the shift toward higher quality, steel manufacturers have developed new technologies and products to meet customer demands. In recent years, by introducing pre-coated steel sheets to products that were conventionally processed from surface-treated steel sheets and then pre-treated and painted, the pre-treatment and painting that were performed in the customer process can be omitted, resulting in lower costs. There is a growing movement toward using prepainted steel sheets to obtain high-quality products. In order to meet these demands, pre-painted steel sheets have traditionally been used, but due to issues such as thorough cost reduction, high-quality appearance, weldability, and handling scratches, there is a growing demand for inorganic colored steel sheets. I came.

As for the color tone, there is a strong need for a black color, and in addition to the above-mentioned characteristics, the material is required to be resistant to fingerprints, workability, chemical resistance, and corrosion resistance.

Conventional methods for coloring stainless steel, steel sheets, and copper are common, but galvanized steel sheets are suitable for this purpose from the viewpoint of cost and corrosion resistance, so the conventional technology for blackening them will be described below. Known techniques for blackening zinc-plated or zinc-alloy plated steel sheets include the method of Japanese Patent Application Laid-open No. 45544/1983, or the method of black chromate treated in an aqueous chromate solution containing silver ions, or the method of Jitsugyo Surface Technology, Vol. 32, No. 10. No. p 541, Table 3, Table 5, etc. These methods involve eutectoiding silver oxide with a chromate film to obtain a black surface. JP-A-52-65139 discloses a method for obtaining a black appearance by forming sulfides. Also, JP-A-58-151490 and JP-A-58-
151491 is a method of blackening by anodic electrolytic treatment. The former is Ni”, Co”, Mo2+ and Zn.
The latter in a 2+ alloy plating bath is a method in which oxides of Ni, Co, and Mo are formed by anodizing a Ni, Co, Mo, and Zn alloy plated steel sheet in an aqueous ammonium sulfate solution. Also, JP-A-60-121
No. 275 discloses a method of chemically dissolving a Ni--Zn alloy plated steel sheet in an aqueous solution of nitric acid or hypochlorite to obtain a black appearance.

(Problems to be Solved by the Invention) The conventional methods described above are not necessarily the best methods and have many problems. For example, methods using silver ions are expensive and have difficulty in high productivity. In addition, anodizing greatly dissolves the plating on the base, which limits the amount of plating on the base and makes it impossible to re-dissolve the plating once deposited.

The present invention solves these problems and provides a colored surface-treated steel sheet that can be processed at high speed and in a short time and is manufactured based on a coloring method that does not depend on the underlying metal.

Alternative Means for Solving the Problems The present invention is based on a method of cathodically depositing a zinc and black compound onto a metal surface. In the past, blackish coloring has been observed due to phenomena such as galvanizing. However, the quality of these materials was literally poor and unreliable, and there was no practical use for them. The invention was successful in obtaining a uniform black coating with good adhesion through the interaction of an alloy plating bath and a water-soluble cationic polymer. The coatings obtained according to the invention are composed of zinc and a colored compound co-integrated with a polymer.

The most important point in the present invention is that a water-soluble cationic polymer is introduced into the alloy plating bath, thereby significantly improving the formation conditions and quality of the colored film.

The present invention will be explained in detail below.

The present invention can be summarized as follows: A colored surface-treated steel sheet and a method for manufacturing the same.

(1) 0, 1t/W consisting of cationic polymer, zinc and coloring compound on the plated or steel plate surface? Colored surface-treated steel sheet characterized by having the above-mentioned composite coating (2) Colored surface-treated steel sheet characterized by having a guard coat on the colored coating described in item 1 - 1〆zLa
-AS,y/[,,''Jllll,i is two trees)Ll,
- Method for producing a colored surface-treated steel sheet (4) 3rd, characterized in that electrolysis is carried out using a plated steel sheet or steel sheet as a cathode in an aqueous solution containing a metal ion with a colored oxide and a pH of 1.5 or more. A method for producing a colored surface-treated steel sheet, which comprises applying a guard coat after washing with water after the electrolytic treatment described in Section 1.The composition of the colored surface-treated steel sheet of the present invention and its formation mechanism will be described.

Zinc ions (Zn2+), blackening metal ions (Men+) and cationic polymer ions (P+) are present in the treatment bath.
Also, an anion (A-) and a proton (H+) are present.

As shown in FIG. 1, zinc is deposited on the cathode surface due to the reduction of metal ions. At the same time, the polymer (symbol ~) is adsorbed to the zinc and precipitates on the surface and a portion together with the zinc. Colored metal ions are reduced, but due to adsorption of polymer ions and preferential precipitation of zinc ions, they are not sufficiently reduced and are precipitated as oxides (symbol -) on which polymers are adsorbed.

Hydrogen oxidation is suppressed by the precipitation of zinc, which has a high hydrogen overvoltage, and a uniform colored film with good current efficiency can be obtained.

FIG. 2 shows a configuration diagram of a colored surface-treated steel sheet.

(a) is a steel plate after coloring treatment (b) is a steel plate coated with a guard coat; (c) is a galvanized steel plate coated with a guard coat.

In the figure, S represents the metal base, B represents the colored layer formed according to the present invention, G represents the guard coat, and Gc represents the chromate film within the guard coat.

2 is a galvanized layer.

The colored layer is a composite film of a metal and a colored compound that are combined with a polymer, and the amount of adhesion varies depending on the degree of coloring. To obtain a colored appearance, a coating amount of at least O, lf/- or more is required. For black appearance, 12/- or more is desirable. Also, depending on the conditions, a semi-gloss gray color can be obtained on the high coating amount side.

The colored surface-treated steel sheet of the present invention includes a steel sheet in which a colored film is coated with a guard coat. The effect of guard coat is
The purpose is to improve quality. For example, by applying a guard coat, the uniformity of the appearance improves and the degree of coloration becomes stronger. Depending on the type and thickness of the guard coat, a steel plate with an appearance ranging from semi-gloss to gloss can be obtained. Also, resistance to scratches is improved. Particularly effective against press, handling, and contact scratches. The effect of improving corrosion resistance is particularly large.

The guard coat of the present invention includes l) a chemical conversion coating, such as a chromate coating, a phosphate coating, a chelate coating, etc., which is formed through a chemical reaction; 2) a resin coating; 3) an inorganic polymer coating; and 4) a composite of resin and inorganic polymer. Film 5) Oil,
These are oils, fats, and waxes, and are composed of a single layer or a multilayered coating of these.

It is necessary to consider the film thickness so that it does not harm the appearance and weldability, etc., and the total thickness is at most 3μ or less, preferably 1.5μ.
It is less than μ.

Resin (organic polymer) is a film made by coating a water-soluble or water-dispersible solvent-soluble organic polymer compound with a curing agent and hardening it by baking, etc., a coating film cured by ultraviolet light, or a composite film made by combining an inorganic-organic compound. It is a film made by coating a polymer with a hardening agent if necessary and hardening it by baking or the like. Compounds include chromium compounds, oxides such as silica, titania, alumina, and zirconia, inorganic compounds such as mica, talc, phosphates, and borates, fatty acid soaps, carbon, fatty acid esters, and organic compounds such as plastic particles. ,Silane coupling agent,
Organometallic compounds such as titanium coupling agents.

Examples of inorganic polymers include silicate compounds and sols of sodium silicate and lithium silicate, condensed phosphoric acid polymers, biphosphates, and zirconic acid polymers.

Known oils and oil waxes may be used.

Further, the colored surface-treated steel sheet of the present invention has a thin colored film and guard coat, so that it is possible to obtain an outer appearance and quality that takes advantage of the surface condition of the base metal, such as gloss and roughness.

The method for manufacturing the colored surface-treated steel sheet of the present invention will be described below.

The processing bath components used in the present invention and their effects will be described.

The water-soluble cationic polymer is a special agent for coloring, especially blackening, and also contributes to smoothing, uniformity, quality, such as densification, slipperiness and corrosion resistance of the coating.

The water-soluble cationic polymer used in the present invention is effectively a polymer of quaternary amine, and the molecular weight is preferably 1 O' to 10' in this case.

Among the following amine polymers, polyamine sulfone (P
AS) and polyamines (PA) are the most effective for blackening. It is thought that the adsorption effect by the amine group and the bond between the sulfone group and the metal ion or metal contribute.

Quaternary amine salt (ammonium salt) Or it is composed of a copolymer.

Some compounds will be specifically listed below.

Examples include polymers obtained from diallylamine. R.I.
*R represents a lower alkyl group or an alkyl group; R,
R2 X is C2-1H8O4-1H, PO, -1R-8O, -
(R is C, %C4 alkyl group), represents an anion of NOl.

Another example is a polymer synthesized from vinylbenzyl. R1+ R2+ R3 represents a hydrocarbon, X is C
J-1H8O4-1H, PO4″″, R-8O8-1N
The anion of O8-1 is shown.

Alternatively, allylamine polymer can be mentioned.

÷CH, -CH-) 1'' R,, R,, R, represents a hydrocarbon, and X is CJ-1H8
It shows anions of O, -1H, PO4-1R-8O3-, No, -.

In addition, polymers of primary, secondary, and tertiary amines are also effective in coloring, although they are not as effective as the quaternary amine polymers described above.

The amount added can be 1 to 200 t/l, but from the viewpoint of black color, a desirable range is 15 to 2 Q''i/L.

5? If it is less than /, it is difficult to obtain a sufficient coloring effect and the appearance tends to be somewhat non-uniform. Moreover, exceeding 20 f/ is undesirable from the viewpoint of liquid viscosity and process considerations.

Next, the metal ion components will be described.

Zinc ions play a vital role. Zinc ions precipitate as zinc at the cathode, suppress hydrogen generation, provide rust prevention, improve current efficiency, and make the appearance uniform.

The amount added is 20 to 150 f/L as subsulfite* (znso, -maH,O), preferably e o to l.
20 f/L.

That is, if it is too low, it will be dominated by the generation of hydrogen gas, and if it is too high, metal zinc will be deposited in large quantities, making it difficult to color.

Next, metal ions whose oxides are colored will be described.

In the present invention, a black film can basically be obtained with a considerable amount of metal ions depending on the electrolytic conditions, but metals having a potential nobler than hydrogen are more likely to precipitate as metals than oxides, making it difficult to do so.

The combined addition of Fe2+ and Cr+3 as coloring ions makes it very easy to obtain a black appearance. In addition, N12+, Co
2+ A black appearance can be obtained by adding molybdenum, vanadium, etc. alone, but it is more stable when they are added in combination.

The concentration is 10~l 5 Q ? in the form of sulfate. /L desirably 20 to 100 t/l is likely to cause blackening.

The pH of the treatment bath must be maintained at 1.5 or higher.

If it is less than 1.5, hydrogen gas is likely to be generated and a colored film will hardly be obtained. A uniform black appearance is easily obtained when the pH is 1.7 or higher, at which hydrogen is difficult to generate. When the pH is in the range of 1.5 to 1.7, there is an advantage that a colored steel sheet with a pattern can be obtained due to precipitation of a colored film and generation of hydrogen gas. If the pH exceeds 3, precipitation occurs and a complexing agent is required.

Electrolytic conditions vary depending on the composition of the treatment bath, and an appropriate current density is determined and the current is applied. On the high current density side, hydrogen generation and zinc precipitation take priority, the blackness becomes lighter, and an appearance with gas patterns is obtained. Further, if the current density is too low, a long processing time is required, so a current density of 2 to 30 A/d- is usually desirable. or,
Although the amount of current varies depending on the bath composition, Zn-Fe-C
Polyamine sulfone polymer of r and quaternary amine (
In the case of a molecular weight of 120,000), there is a condition where it can be obtained at 25 coulombs/d- or more.

Coloring can be achieved with a smaller amount of current than conventional anodizing methods.

As a result of attempts to treat cold-rolled steel sheets, zinc alloy-plated steel sheets, galvanized steel sheets, bright galvanized steel sheets, tin-plated steel sheets, etc., the surfaces to be treated were all colored and black, and the cold-rolled steel sheets and zinc alloy-plated steel sheets had black spots. , it was excellent in terms of scratch resistance.

In the case of the present invention, other compounds may be added if necessary for the following purposes. Various supporting salts to increase the conductivity of the solution, borates, phosphates, and phthalates as pH buffering agents, phosphates, chromic acids, and inorganic sol to increase rust prevention and adhesive strength with guard coats. compounds, chelating agents to prevent precipitation, etc.

FIG. 3 shows the effect of the cationic polymer of the present invention on blackness (L value). The treatment bath was zn2 +.

The test was carried out in a sulfuric acid bath containing Fe2+ and cr+3 ions at a pH of 2.8. The solid line (-) in the figure is a current density of 12 (pyarr?) and an energization amount of 47 (coulomb 1arr?).
r? ) is deposited using an electrogalvanized steel sheet as a cathode. The broken line (...Δ...) indicates the amount of current 70
(coulomb/drr?). As the cationic polymer, a quaternary amine polyamine sulfone (abbreviated as PAS) with a concentration of 3.0% was used. With this composition and electrolytic conditions, when the amount of PAS added is "0", there is almost no coloring (L value = 43), but when more than 12 t/ of PAS (30%) is added, the black appearance with an L value of 25 or less. was gotten. It can also be seen that the same tendency is shown even when the current density is changed.

Further, FIG. 4 shows the relationship between the amount of current and the L value. The processing bath is the third
Containing the metal ions shown in the figure, the concentration of PAS (30%) was 20%.
It was fixed at 2μ. pH was 2.8.

The plate to be treated is an electrogalvanized steel plate. In the figure [−・−
] was applied continuously at a current density of 12 A/d- [
...[Phase]...] is an example where the current is applied in two steps (40 coulomb field energization 20 → pause → energization 20) [△
1 Ro, X] is an example in which the current density was 19.24°9A/dm'' intermittently. All samples exhibited a black appearance with an L value of 25 or less.

Coating methods for Guard Coat include well-known roll coating, roll squeezing, spraying, air knife squeezing,
After coating by dipping, electrolytic treatment, or electrostatic coating, heating (hot air, infrared rays, combustion furnace, electric heating), ultraviolet curing, etc. can be employed as necessary.

Examples are given below.

The symbols and abbreviations in the examples will be explained.

In the bath composition, PA stands for polyamine polymer and PAS stands for polyamine sulfone polymer.

The current density is expressed as DK and the unit is Al4-. The amount of energization is indicated as Q, and the unit is coulomb 1ard. 23×2 is 2
This means that 3 coulombs were energized twice.

The L value was measured by lightness using a commercially available color difference meter. In relation to blackness, the L value must be 25 or less.

Among the guard coats, the chromate is a composite chromate consisting of silica and chromic acid, which is deposited as Cr for 10m97m, and the phosphate film is a commercially available coated phosphate film.
Chelation treatment is tannic acid treatment.

A commercially available clear coating was used as the polymer coating. The film was coated with a target thickness of about 1 μm.

Example 1 A cold-rolled steel sheet was electrolytically galvanized in a sulfuric acid bath by a known method, washed with water, and immediately subjected to the coloring treatment shown in Table 1. In the electrolytic treatment, electricity was applied using the sample as a cathode and the lead plate as an anode.

After coloring, the sample was washed with water and dried with hot air, and the color value was measured using a color difference meter.

Floors 1.17, 21, and 23.24 do not meet the conditions of the present invention, so the L value is large and a colored appearance cannot be obtained.

Ugly 2 to 4 have a slightly high L value and a yellowish black appearance due to the small amount of PAS added. ? 15-16 has an L value of 2
It has a jet black appearance, which is less than that of 5. The film was dense, slippery, and had good adhesion. -18 to 20 and 22.25 are examples of the present invention with different compositions.

High 25' is a comparative example in which the pH of Na25 is lowered to 1.5 by adding sulfuric acid and cannot be colored.

Example 2 12%Ni with the N11B composition and processing conditions of Example 1
- When applied to Zn alloy plated steel sheets and cold-rolled steel sheets, black appearance with L values of 17.6 and 16.9 was obtained. Scratches caused by the steel plate edge were difficult to enter and were not noticeable. Further, as a result of applying the test to a bright galvanized steel sheet and a tin-plated steel sheet under the conditions of ms, a black appearance with a density value of 19.7 and 21.3 was obtained.

Example 3 An electrogalvanized steel sheet obtained from a sulfuric acid bath was subjected to the coloring treatment shown in Table 2. After treatment, it was washed with water and the L value was measured.

Na26 to Na28 were comparative examples that did not contain PAS and had a pale green white appearance and a powdery appearance with poor adhesion.

Samples Nos. 29 to 31 added PAS and obtained a black, smooth surface with a low L value.

Example 4 After blackening treatment using ms in Example 1, a guard coat as shown in Table 3 was applied. The L value was further lowered, the degree of blackness increased, and the adhesion and corrosion resistance were improved.

The guard coats in Table 3 are as follows.

A: Film of water-dispersed imine-modified acrylic acid copolymer, silica, and silane coupling agent B: Lithium silicate (commercial product) C: Film formed from water-soluble acrylic ester copolymer, calcium stearate, and hardening agent f 'l'J so i ・not ・so 1)-h
Both and seedling E: Oiling F: Copolymer of water-soluble polyacrylic acid and its ester and C
r” aqueous solution G: Apply 1μ of guard coat of A after chromate H: Apply 1μ of guard coat of A after phosphate treatment using commercially available coating J: Apply 1μ of guard coat of A after electrolytic chromate The value is brightness and gloss. indicates the gloss value when the black glass plate is set to 93, and all were in accordance with the method determined by JIS.

Adhesion was evaluated by peeling with 2T folding cellophane tape: O: no peeling, ×: peeling.

Corrosion resistance is 5% white rust using JIS standard salt spray test.
The evaluation was based on the time until the occurrence of the disease, and a score of 3 was 72 hours or more, a score of 2 was 24 to 48 hours, and a score of I was less than 24 hours.

Fingerprints that remain are shown as (×), and those that do not stick or can be wiped off are shown as (0).

Also, weldability is spot weldable (○).
It was shown in

N [132 to 41 were coated with a guard coat, and in particular, after chromating, a water-dispersible acrylic copolymer, silica, and a silane coupling agent were coated.

Samples Nos. 39 and 41 showed excellent overall performance.

Example 5 ZnSO4H7H20/Fe50. H7H2o/40
% Cr2 (804) liquid = 80/40/40f/L
A 25% aqueous solution Q20 of a quaternary amine polymer (abbreviation: PA, molecular weight approximately 20,000) in an aqueous solution with pH = 2.02
Electrogalvanized steel sheet in a bath containing f/, 50 coulombs/dm at 12A/dm' using a bath-dip galvanized steel sheet as a cathode.
a m' energized. A surface-treated steel sheet having a black surface with a value of 22 to 21 was obtained in both cases. For comparison, thiourea, urea, and triethanolamine were each used at 4 t/g instead of PA.
Electrolysis was performed in each bath containing
Only 70 appearances were obtained.

(Effects of the Invention) The colored surface-treated steel sheet according to the present invention has excellent appearance, workability, and corrosion resistance, and is a new type of steel sheet that has strong resistance to scratches and can be used in the field of conventional coated steel sheets to improve the quality of products. , contributing to low costs.

In addition, since high-speed and short-time processing is possible in manufacturing, processing can be performed within a conventional electroplating line, and manufacturing can be performed at low cost.

In particular, the present invention is advantageous over conventional alloy plating or alloy melting methods in that it does not depend on the base metal and can easily color the surface to which electricity is applied.

[Brief explanation of the drawing]

FIG. 1 shows a diagram estimating the coloring mechanism of the present invention and the structure of the film, which is a composite structure of metal and oxide with a polymer adsorbed thereon. Moreover, FIG. 2 shows the structure of the colored surface-treated steel sheet of the present invention, in which (,) shows the steel plate colored and (b) shows the steel plate coated with a guard coat. (C) is a colored galvanized steel plate with a two-layer guard coat. Figure 3 shows the relationship between the amount of polyamine sulfone added as a quaternary amine polymer, which is one of the bath compositions of the present invention, and blackness.The addition of this polymer is essential for blackness. This is what is shown. FIG. 4 shows the relationship between the amount of current applied and the degree of blackness when electrolyzed in a typical bath used in the present invention. It was shown that coloring can be done efficiently with a small amount of current applied. Figure 1 Figure 2

Claims (4)

[Claims] (1) A colored surface-treated steel sheet characterized by having a composite coating of 0.1 g/m^2 or more consisting of a cationic polymer, zinc, and a colored compound on the plated or steel sheet surface. (2) A colored surface-treated steel sheet according to claim 1, which has a guard coat on the colored film. (3) A colored surface-treated steel sheet characterized by electrolysis using a plated steel sheet or a steel sheet as a cathode in an aqueous solution containing a water-soluble cationic polymer, zinc ions, and metal ions with coloring oxides and having a pH of 1.5 or more. manufacturing method (4) A method for manufacturing a colored surface-treated steel sheet according to claim 3, which comprises applying a guard coat after washing with water after electrolytic treatment.