JPS6350499A - Colored zinc composite plated steel sheet and its production - Google Patents

Abstract

PURPOSE:To obtain a blackened Zn composite plated steel sheet having fine appearance, superior workability and corrosion resistance by electrolyzing a steel sheet as the cathode in an acidic aq. soln. contg. Zn ions, coloring metal ions and highly oxidative ions. CONSTITUTION:A steel sheet, a stainless steel sheet or a steel sheet plated with Zn, Al, Sn or the like is immersed in an acidic plating soln. of 1-4pH contg. 20-100g/l Zn ions and 10-50g/l ions of one or more kinds of coloring metals such as Ni, Co, Fe, Cr, Sn and Cu in 0.1-1.0 ratio of coloring metal ions to Zn ions, and further contg. 1-50g/l highly oxidative ions such as NO3, NO2, ClO4 or ClO3 ions and a specified water soluble high molecular compound as a brightener. Electric current is then supplied at 10-100A/dm<2> current density with the steel sheet as the cathode to form blackened composite plating contg. Zn and the coloring metals as the principal components, and the plated steel sheet is coated with a guard coat of <=3mum thickness such as film formed by chemical conversion treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a mixed color, 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 lowering costs year by year,
Moving toward higher quality, steel manufacturers have developed new technologies and products to meet demand X. In recent years, by introducing pre-coated steel sheets to products that were previously processed from surface-treated steel sheets and then pre-treated and painted,
There is a growing movement towards pre-painted steel sheets, which eliminates the pre-treatment and painting that were previously performed in the consumer process and allows the production of high-quality products at low cost. 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 strong demand for inorganic colored steel sheets. It has come.

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 of 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. .

A known technique for blackening zinc-plated or zinc alloy-plated steel sheets is disclosed in Japanese Patent Application Laid-Open No. 52-455 as a black chromate treatment in an aqueous chromate solution containing dominant ions.
The method described in Publication No. 44 or Practical Surface Technology Journal 3
There are techniques described in Vol. 2, No. 10, p. 541, Table 3, Table 5, etc. These methods involve eutectoiding silver oxide with a chromate film to obtain a black surface. A method for obtaining a black appearance by forming sulfides is described in JP-A-52-65139. Furthermore, Japanese Patent Laid-Open No. 58-151490 and Japanese Patent Laid-Open No. 58-151491 disclose a method of blackening by anodic electrolytic treatment. The former is Ni”, C
The latter is a method of forming oxides of Ni, Co, and Mo by anodizing a steel plate plated with an alloy of Ni, Co, Mo, and Zn in an aqueous ammonium sulfate solution in an alloy plating bath of Zn"+. In addition, JP-A-60-121275 discloses a method for obtaining a black appearance by chemically dissolving a Nl-Zn alloy plated steel sheet in an aqueous solution containing nitric acid or hypochlorous acid groups. .

In addition, Japanese Patent Application Laid-Open No. 60-200996 discloses that Zn" and N
15% JNi by cathodic electrolysis in a 1' alloy plating bath.
A method for blackening a galvanized steel sheet by obtaining an alloy galvanized steel sheet containing the above is disclosed.

(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 achieving high productivity. In addition, in the case of the positive treatment, the plating on the substrate is largely dissolved, which limits the amount of plating on the substrate, and it is impossible to re-dissolve the deposited plating.

In addition, in the method of JP-A-60-200996, since the resulting film is a black alloy plating film of Ni and Zn,
This method is difficult to produce because it requires limited current density and bath temperature to obtain a black color, and the base plating is limited to zinc or zinc-based alloy plating.

The present invention solves these problems and provides a colored surface-treated steel sheet manufactured based on a coloring method that is capable of high-speed, short-time processing and does not depend on the underlying metal.

(Means for Solving the Problems) The steel sheet of the present invention is produced by using a steel sheet or a plated steel sheet as a cathode in an acidic aqueous solution containing colored metal ions represented by Zn2 and Me and strongly oxidizing ions represented by OX. It has a colored composite plating film of 0.1 to 5 g/m3 whose main components are zinc and colored oxide obtained by electrolysis,
A colored zinc composite plated steel sheet is characterized in that it has a guard coat of 3μ or less on the coating. In the acidic aqueous solution, Men+ is Ni”, Co”→, Fe”, Fa
", Cr", Sn", Cu" or more, OX No. 8. NO□-ICtO4 Otsu C2O! It is preferable that the aqueous solution is either 3'-.

In the manufacturing method of the present invention, Zn is 20 to 1 o y
74M6” is 10-509/l and Mer7Zn2+
The ratio is 0.1 to 1.0, and the OX is 1 to 502/l.
i!c flow density 10 to 100 using a steel plate or plated steel plate as a cathode in an acidic aqueous solution with p) (=l to 4) as the main component.
This is a method for producing a colored zinc composite metal sheet, which is characterized in that it is electrolytically treated at A/day at 20 to 200 coulombs/d, washed with water, and then coated with a guard coat of 3 μm or less. Me is N+, Co, Fe.

p6", Cr", Sn", Cu"O1g or more, OX is N
O3゜No 2-, Cto 4-, CzO32
- It is preferable that it is one type. It is also preferable to add a brightener to the acidic aqueous solution.

The invention is based on the cathodic deposition of zinc and black oxide onto metal surfaces. In the past, black-colored metal blemishes have been observed due to phenomena such as rough plating burnt in galvanized crystals. However, the quality of these materials was literally poor and uneven, and they were of no practical use.

The present invention has succeeded in obtaining a uniform black coating with good adhesion through the interaction of an alloy plating bath and a water-soluble cationic polymer. The coating obtained by the present invention is composed of a composite plating coating of zinc combined with black oxide.

The most important point of the present invention is that water-soluble strong oxidizing anions are introduced into the alloy plating bath containing metal ions whose oxides are black, thereby significantly improving the formation conditions and quality of the colored film. be. The present invention will be explained in detail below.

(Function) The composition and formation mechanism of the colored surface-treated steel sheet of the present invention will be described.

Zinc ions (Zn''), blackening metal ions (Me), strong oxidizing ions (OX), protons (H
) exists.

As shown in FIG. 1, zinc is deposited on the pole surface due to the reduction of Zn2. At the same time, colored metal ions (Me) are also reduced, but due to OX in the plating bath, they are oxidized at the same time as they are precipitated, and Men (marked with .), which is mainly an oxide, is precipitated. A portion of zinc also precipitates as ZnO, but since the reduction potential is sufficiently low, it preferentially precipitates as zinc. Hydrogen evolution is suppressed by zinc deposition with high hydrogen overpotential.

Men+ is oxidized by OX and colored Ni", CoSFe2. Fe', Cr3. Sn", Cu"
They can be colored alone or in combination.

OX is a strongly oxidizing 7-ion, NO3-, NO2-, Cr
04-.

This is an aqueous solution containing one type of Cz03-.

In the present invention, zinc plays the role of a color vehicle for the colored composite plating film. If the mixing ratio of oxide and zinc is inappropriate,
Powdering occurs on the surface layer. A colored film with good adhesion can be obtained by selecting an appropriate Me 2 /Zn ratio, appropriate oxidizing power, and pH.

Also, adding a brightener to the plating bath will make the composite plating film denser and improve its quality.

FIG. 2 is a configuration diagram of a colored surface-treated steel sheet. S is the base metal material, such as thin steel plate, stainless steel plate, plated steel plate,
For example, zinc and zinc alloy plated steel sheets, aluminum and aluminum alloy plated steel sheets, tin, lead plated shoulder plates. B
G is a colored zinc composite plating layer formed according to the present invention;
is a guard coat, Gc indicates a chromate film within the guard coat, and 2 is a plating 79.

Figure 2 (,) shows an example in which a steel plate is directly colored. The same figure (b
) shows an example in which a plated steel plate is colored, and (C) in the same figure shows an example in which B is subjected to chromate treatment and covered with a guard coat.

It is a composite film of metal and colored compound, and the amount of adhesion varies depending on the degree of coloring. At least 0.1 to obtain a colored appearance?
/lr? A greater amount of adhesion is required. 1 for black appearance.
0 f/- or more is desirable.

If the extra gold plating film is too thick, a surface powdering phenomenon called flea laddering will occur, so 5y/ff11 or less is suitable.

The colored zinc composite plated steel sheet of the present invention has a guard coat coated on the colored composite plating film. The purpose of the guard coat 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 copper plate with an appearance ranging from semi-gloss to gloss can be obtained. Also, resistance to scratches is improved. % effective against press, handling, and contact scratches. The effect of improving corrosion resistance is particularly large.

The guard coat of the present invention includes (1) a chemical conversion coating, for example, a coating formed through a chemical reaction such as a chromate coating, a phosphate coating, a chelate coating, (2) a resin coating, (3) an inorganic polymer coating, ( 4) Composite coating of resin and inorganic polymer; (5) Dust made of oil, oil, fat, wax, etc., and these coatings may be used alone or in multiple layers.

The film thickness must be carefully considered so as not to harm the appearance and weldability, and the total thickness should be at most 3μ or less, preferably 1.
It is 5μ or less.

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 rays, or a composite film with an inorganic organic compound. This is a film made by coating a composite polymer with a hardening agent if necessary and hardening it by baking, etc. Compounds to be combined include chromium compounds, oxides such as silica, titania, alumina, and zirconia, inorganic compounds such as mica, Merck, phosphates, and borates, fatty acid stones, carbon, fatty acid esters,
These are organic compounds for plastic particles, and organometallic compounds such as silane coupling agents and 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.

In addition, the colored zinc composite plated steel sheet of the present invention has a thin colored composite plating film and guard coat, so it has the characteristic that it can obtain an 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 zinc composite plated steel sheet of the present invention will be described below.

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

Zinc ions play a vital role. Zinc ions precipitate as zinc at the cathode, suppressing hydrogen generation and providing anti-rust properties, as well as acting as a binder for the coating, improving current efficiency, and making the appearance uniform.

The amount added is 20-1009/l as Zn' and 88-440/l as zinc sulfate (ZnSo4.7 H2O). /l
Z is preferably 30 to 90 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, there will be a lot of metal zinc deposited, making it difficult to color.

Next, colored metal io/Me will be described.

In the present invention, a black-colored coating can be obtained by using metal ions (possible), among which Ni'', Co2゜Fe''
, Fe'', Cr3+, Sn'', and Cu'' are suitable for obtaining black color.The concentration is 1.
0 to 50 t/l, the balance with Zn2 is Me”
/ Z n''+ ratio is 0.1 to 1.0. The desirable ratio is 0.2 to 0.5, and the more 2n2 is, the easier it is to obtain a high quality black film. That is, the lower Me/Zn' If it is too high, the blackening will be insufficient, and if it is too high, a dull ring will occur.

Zn”, Me can be supplied by sulfate, chloride,
Phosphates and sulfonates, and carbonates, oxides, hydroxides, metal powders, etc. can be used as supplements.

OX is NO”3. NO2-, Ct04-, Ct03
An ion selected from ``-'', supplied as a soluble salt or acid.

The appropriate concentration of ions is 1 to soy/l.

If it is less than 1 y/, sufficient oxide is not formed and no coloring occurs. Moreover, if it exceeds 502/, all the metals will be oxidized, making it difficult to color and easily causing powdering.

Preferred concentrations are 5-30 y/l to obtain a black color.

OX is consumed in the genital area, so replenish it.

The pH of the aqueous solution is 4 or less, at which metal salts do not precipitate, and 1 to 4, at which metal precipitation is likely to occur.

Although the bath temperature can be colored over a wide range, it is preferably 30 to 60°C.

The colored film obtained by the method of the present invention is Zn''.

By using an acidic aqueous solution containing a brightener in addition to Me'' and OX, the quality, especially gloss, noggrading, and adhesion to the guard coat, can be improved.

Examples of brighteners include water-soluble polymer compounds such as cationic quaternary ammonium salt diamine polymers, polyamine sulfone polymer compounds, nonionic polyacrylamide compounds, and combinations of these and anionic polymers. Copolymers, aldehydes, phenolic compounds, and sulfonic acid compounds known as known brighteners can be used.

The amount added varies depending on the type of compound, 10 to 4000
Add as appropriate within the range of 0 ppm.

The electrolysis conditions will be described below.

The present invention is an excellent method that can set a wide range of conditions for a colored region compared to conventional methods. Current density is 10-10
0/dm''.If it is less than 10A/drr, coloring will be severe.If it is more than 100A/dr, hydrogen gas will be generated.
There is a high risk that the formed film will come off. The amount of electricity is 20~2
00 coulombs/d-.

If the content is less than 20 Cron/dffII, coloring is difficult and tends to result in uneven appearance. Also, 200 coulombs/dff11
At higher temperatures, pinhole damage due to film removal and hydrogen gas tends to occur.

The flow rate may be either a static bath or a high flow rate.

As a result of trying his treatment on cold rolled steel sheets, zinc alloy plated steel sheets, galvanized steel sheets, bright galvanized steel sheets, tin plated steel sheets, etc., all of them were colored, and in the case of black, cold rolled steel sheets and zinc alloy plated steel sheets were black. It was excellent in terms of scratch resistance and scratch resistance.

In the process of the present invention, other compounds may be added as necessary for the following purposes. Various supporting salts to increase the conductivity of the solution, borates, phosphorus salts and phthalates as pH buffering agents, polymers to improve adhesion resistance, rust prevention and adhesive strength with guard coats. These include phosphates and chromic acid, inorganic sol compounds, cationic polymers, chelating agents to prevent precipitation, chlorides and fluorine compounds that provide smoothness to the zinc composite plating film formed.

Coating methods for card coating include roll coating, roll squeezing, spraying, air knife squeezing,
After applying by dipping, electrolytic treatment method, or electrostatic coating method,
If necessary, heating (heat, lice, infrared rays, incinerator, electric heat) or ultraviolet curing can be employed.

(Example) Examples are given below.

Unless otherwise specified, baths for '), Zn'', and Me were prepared from sulfates, and for OX-, a sodium salt was used.

The current density is indicated as Dk, and the unit is A/d-.

The amount of energization is indicated as Q, and the unit is coulomb/d-.

The amount of attached colored zinc composite plating was expressed as CW, measured by gravimetric method, and expressed as 2/fud.

, L value is the brightness and was measured using a commercially available color difference meter. In relation to blackness, the L value must be 25 or less.

For Examples without particular explanation, the following guard coating was applied.

The chromate of the guard coat was a composite chromate consisting of silica and chromic acid, which was deposited as Cr at a rate of 20 μ/d, and the polymer film was a commercially available water-based olefin acrylic and silica sol clear coating. The abdomen is about 1
Apply roll coating with μ as the target value, and use hot air to heat the board to 10
I baked it aiming for 0℃.

Among the quality, adhesion was evaluated by peeling off the tape after bending at 180 degrees and visually evaluating the following: O (no peeling) Δ (tape attached in dots) × (complete peeling).

Corrosion resistance was tested using a continuous salt spray test in accordance with JISZ 2371 standard, and was expressed as the time required for 5% rust to occur in terms of area ratio.

Example 1 A cold-rolled steel sheet was electrolytically galvanized in a sulfuric acid bath using a known method, washed with water, immediately subjected to the coloring treatment shown in Table 1, and then coated with a guard coat and baked. 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 its value was measured using a color difference meter.

1 to 5 are Zn” using sodium nitrate as OX.
This is data when changing the ratio of + and Ni2+, Ni”
/Zn2=low L value appearance is obtained in the range of 0.2 to 1.0. -56-9 are examples in which the current density was changed from 10 to 100 A/dm' using a bath of Zn2 and Fe2, and the current density was changed to 10 A/dm'.
d- tends to have a slightly higher L value, 100A/
In d-, point-like peeling begins to occur. A10 has a pH of 1
．． In the example with 2 K, a low pI (but a low value was obtained.All indicates an example that does not contain OX, and only a high L value can be obtained.

A12.13 is an example using a composite bath as Me,
A low L value is obtained.

A 14 to 18 are data obtained by changing Zn"ii and Fe/Zn2+ ratio. If Zn" is too low, it becomes whitish. When Suru approaches 3, the L value becomes high.

A19 is a composite addition bath of Me"+, Fe"+ and Fe3+, and the influence of Fe3 is small.

420-22 are NOZ-, C604- as OX.

In the example using C101+ and Fe"+, No2- and ClO2"-, which have a weak oxidizing effect, tend to have slightly higher L values than S and ClO4 and NO3-.

A23-24 are Ni2+, Co” as Δ■en+
tJ) This is an example of a case where multiple additions are made and the pH is changed. At around pH=1, the L value is high and etching occurs, resulting in unevenness.

/i 25 to 30 are examples in which the concentration of NO3 is changed as OX, and NO3 has a high L value in a bath of so, 1o0r/z, and falls at the limit value. NO3- is 5,10゜2 o y
/l, a sufficient L value is obtained.

A31 to A33 are examples in which the amount of coulombs was changed; at 25 coulombs, the L value was slightly high, and at 200 coulombs, bag ring occurred.

Example 2 Zinc sulfate 400? /l (Zn292), 'jdi nickel 100? /L (Ni”20), Ni
2”/ l n 2 + Hiho 22, NaNO320r/
Electrolytic treatment (50 A/drr/, 50 coulomb/
dm') After that, the same Gar P coating as in Example 1 was applied.

Table 2 This treatment method was not dependent on the metal to be treated and was able to color steel plates and plated steel plates.

Example 3 The same treatment as in Example 2 was carried out on the 12th night using Solution A, in which 8000 ppm of a commercially available polyamine sulfone polymer was added to the acidic aqueous solution used in Example 2, and BO, in which 20 m of polyacrylamide was added. N I Z rr %
% went to plated steel plate.

L value is A=11. With B=12, a black steel plate with semi-gloss and excellent workability was obtained.

(Effect of the invention) The colored galvanized steel plate according to the present invention has a good quality appearance and
As a new @ plate with excellent workability, corrosion resistance, and strong resistance to scratches, it can be used in the conventional coated copper plate field, contributing to higher quality products and lower costs.

In addition, since a very wide range of processing conditions can be applied to manufacturing, and high-speed and short-time processing is possible, 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 coloring does not depend on the base metal and the surface to which electricity is applied can be easily colored.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the coloring mechanism of the present invention and the structure of its coating, and Fig. 2 (a), (b), and (c) are diagrams showing the structure of the colored zinc composite plated steel sheet of the present invention. It is. Agent: Patent attorney Masamitsu Akizawa and one other person Figure 7I'2

Claims (5)

[Claims] (1) By electrolyzing a steel plate or plated steel plate as a cathode in an acidic aqueous solution whose main components are colored metal ions represented by Zn^2^+ and Me^n^+ and strongly oxidizing ions represented by OX. It has a colored composite plating film of 0.1 to 5 g/m^3 mainly composed of zinc and colored oxide obtained by
A colored zinc composite plated steel sheet having a guard coat of 3μ or less on the coating. (2) The acidic aqueous solution is Me^n^+, Ni^2^+, C
o^2^+, Fe^2^+, Fe^3^+, Cr^3^
+, Sn^2^+, Cu^2^+, OX is N
O_3^-, NO_2^-, ClO_4^-, ClO_
3. The colored zinc composite plated steel sheet according to claim 1, which is an aqueous solution of either of the following. (3) Zn^2^+ is 20 to 100 g/l, Me^n^
+ is 10 to 50 g/l and Me^n^+/Zn^2^
+ ratio is 0.1 to 1.0 and OX is 1 to 50 g/l
Current density is 10 to 100 A/d using a steel plate or plated steel plate as a cathode in an acidic aqueous solution with a pH of 1 to 4 containing as the main component.
Electrolytic treatment at 20 to 200 coulombs/dm^2 at m^2,
A method for producing a colored zinc composite plated steel sheet, which comprises washing with water and then coating with a guard coat of 3μ or less. (4) Me^n^+ is Ni^2^+, CO^2^+, F
e^2^+, Fe^3^+, Cr^3^+, Sn^2^
One or more types of +Cu^2^+, OX is NO_3^-, NO
3. The method according to claim 3, which is one of _2^-, ClO_4^-, and ClO_3^2^-. (5) The method according to claim 3, wherein a brightening agent is added to the acidic aqueous solution.