JPS63153295A - Manufacturing method of colored coated steel sheet with excellent chemical conversion treatment properties - Google Patents

Abstract

PURPOSE:To produce the title coated steel sheet having an excellent coloring characteristic such as black in a short time by electrolyzing the steel sheet in an acidic bath wherein the contents of Me and Zn and the ratio of both metals are specified, chemical conversion coating the sheet, and then applying a guard coat to the sheet. CONSTITUTION:An aq. acidic soln. kept at 1-4pH, contg. 10-90g/l Zn<2+> and 10-100g/l Me<n+>, wherein the ratio of Mn<n+>/Zn<2+> is controlled to >=1, and consisting essentially of 1-50g/l OX is prepared. One kind among Ni<2+>, Co<2+>, Fe<2+>, Sn<2+>, and Cu<2+> is exemplified as the Me<n+>, and one kind among NO3<->, NO2<->, ClO4<->, etc., is used as the OX. A steel sheet or a plated steel sheet is electrolyzed in the aq. soln. at 5-100A/dm<2> current density and 20-200 coulomb/dm<2> quantity of electricity with the plated steel sheet as a cathode, and a film consisting essentially of a coloring oxide is formed at 0.1-5g/m<2> deposition quantity. The sheet is washed with water, applied with chemical conversion coating such as chromating, and then coated with a guard coat having <=3mu thickness. The obtained colored coated steel sheet has excellent appearance, workability, and corrosion resistance, and is highly resistant to cracking.

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 rust-proofing steel sheets, household steel sheets, furniture, and building materials. ,
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 previously 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 strong demand for inorganic colored steel sheets. Next time.

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 known as a method 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 silver ions.
There is a method described in Publication No. 44, or a technique described in Jitsugyo Surface Technology Journal, Vol. 32, 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 in an alloy plating bath of Ni2+, Co2+9Mo2+, and Zn2+, and the latter is in an alloy plating bath of Ni, co, Mo, and Z.
This is a method in which atomized products of Ni, Co, and Mo are formed by anodizing an alloy-plated steel sheet of n in an aqueous ammonium sulfate solution. Also, JP-A-60-1212
Publication No. 75 describes Ni-Z using an aqueous solution of nitric acid or hypochlorite.
This disclosure discloses a method for obtaining black outer 'R' by chemically melting an alloy-plated steel plate of n.

In addition, Japanese Patent Application Laid-open No. 60-200996 discloses that Zn2+ and Ni
This patent discloses a method of blackening an alloy galvanized steel sheet containing 15 or more Ni gold by cathodic electrolysis in a 2+ alloy plating bath.

(Problem to be solved by the invention 2) The conventional methods described above cannot necessarily be said to be the best methods and have many problems. For example, the method using silver ions is expensive and does not have high productivity. In addition, anodizing causes a large amount of dissolution of the plating on the base, which limits the plating on the base, and it is difficult to re-dissolve the plating once deposited.

In addition, in the method of JP-A-60-200996, since the obtained skin is a black alloy plating film of N1 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 point between m) The steel sheet of the present invention is a steel sheet or a plated steel sheet in an acidic aqueous solution containing colored metal ions represented by Zn2+ and Me'+ and strongly oxidizing ions represented by OX as main components. Deposition to, t ~ 5 t obtained by electrolyzing with □ as a cathode
Ar? This is a colored coated steel sheet characterized by having a coating mainly composed of a colored oxide, and having a chemical conversion treatment and a guard coat of 3μ or less on the coating. Me'+ in the acidic aqueous solution is Ni2+.

c02+, Fe2+, Fe3+, cr3+, sn2+,
One or more types of cu2+, OX is No3-, No2-,
It is preferable that it is either ClO4- or 0103'-.

In the production method of the present invention, Zn2+ is 10 to 90'I/l
, n+ Me is 10 to 100 f/l and Me ”/Z
In an acidic aqueous solution with a pH of 1 to 4 containing n2+ ratio of 1 or more and OX- as a main component of 1 to 50 t/l, a current density of 5 to 10oA/dr1? using a steel plate or plated steel plate as a cathode. So 2o~2o.

Coulomb/dm' Electrolytic treatment, washing with water, chemical conversion treatment, and subsequent coating with a guard coat of 3 μ or less ft! Craftsmanship of colored coated steel plate with TP characteristics Mann+2
+2+2+50 This is the square method. Me is Ni, co, Fe,
Fe, Or.

Sn", one or more of Cu2+, OX is No3-, N
o2-, 0104-.

Preferably, it is one type of C2O4.

By adjusting the surface roughness of the steel plate or plated steel plate, a colored appearance with a high-class image can be obtained.

A glossy appearance is obtained with an average roughness of 1μ or less, and a semi-gloss appearance is obtained with an average roughness of 1.5μ or more.

The present invention is based on the cathodic deposition of black oxides of Zn and Me onto metal surfaces. Conventionally, a blackish color has been observed due to phenomena such as rough plating crystals caused by zinc plating, etc. However, the quality of these materials was literally poor and unreliable, and there was no practical use for them. The present invention has succeeded in obtaining a uniform black coating with good adhesion through the interaction of the alloy plating bath and oxidizing ions.

The most important point of the present invention is that water-soluble strongly oxidizing anions are introduced into a zinc alloy plating bath containing metal ions whose oxides are black, thereby significantly improving the conditions and quality of forming a colored film. It is.

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, (zn2+)s blackening metal ions (Men+), strong oxidizing ions (OX), and protons (H+) are present in the treatment bath.

As shown in Figure 1, on the cathode surface, zinc and colored compounds f
fi(Me) is precipitated by reduction, but OX in the plating bath
Therefore, it is oxidized at the same time as it is deposited, forming zinc oxide (+l) and MeO oxide (marked with a mark), which is mainly an oxide.Although a very small amount of metal may remain, most of it is oxide.

Hydrogen evolution is suppressed by the initial precipitation of zinc with a high hydrogen overpotential.

Me”+ is Ni2+, which is oxidized with OX and becomes colored.
002+.

Fe2+, F,3+, C,3+, Sn2+, C
Coloring can be achieved by using u2+ alone or in combination. oX is a strong oxidizing anion, No3-,
No2-, 0404-.

This is an aqueous solution containing one type of CZO3-.

If the precipitation ratio of zinc oxide and colored metal oxide in the oxide is inappropriate, the film tends to be sensitive to the chemical conversion treatment and guard coating in the next process. This can be achieved by selecting

FIG. 2 is a configuration diagram of a colored surface-treated steel sheet. S indicates the base metal material, such as a thin slab or stainless steel plate, and 2 indicates the plating layer. Examples of plating include zinc and zinc alloy plated steel sheets, aluminum and aluminum alloy plated steel sheets, tin and lead plated steel sheets.

B is a colored coating layer formed according to the present invention, G is a guard coat, and Gc is a chemical conversion coating.

FIG. 2(a) shows an example in which a steel plate is directly colored. The same figure (b
1 is an example of a colored plated steel plate.

The depth of coloring varies depending on the amount of oxide deposited. To obtain a colored appearance, a coating amount of at least 0.1 f/d is required. 1.0 f/n in black appearance? The above is desirable.

If the film is too thick, a surface powdering phenomenon called powdering will occur, so 59/rr? The following are appropriate.

After forming a black film by electrolysis, a chemical conversion treatment is immediately performed. Chemical conversion treatment is carried out by the coating chromate method, in which a chromate solution containing a water-soluble chromium compound as the main component is applied and then dried with waterless washing, the etching chromate method, in which a chromate solution is reacted and then washed with water, or the electrolytic treatment, in which electrolytic treatment is performed in a chromate solution. Includes chromate or phosphate treatment. Chromate treatment tends to increase blackness and is advantageous for black appearance.

A guard coat is then applied. 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 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 significant.

The guard coat of the present invention includes (1) a resin coating, (2) an inorganic polymer coating Ws (3> a composite coating of resin and inorganic polymer,
(4) Oils, fats and waxes, and are composed of single or multi-layered coatings 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.
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, talc, phosphates, and borates, fatty acid soaps, carzene, 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 zirconate polymers.

Known oils and oil waxes may be used.

Furthermore, since the colored coating and guard coat of the colored coated steel sheet of the present invention are thin, it is possible to obtain an appearance and quality that takes advantage of the surface condition of the base metal, such as gloss and roughness. In particular, there is a strong demand for a semi-gloss appearance, which can be achieved by increasing the average surface roughness to 1.5 μm or more.

The method for manufacturing the colored coated 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 initially precipitate as zinc at the cathode, suppressing hydrogen generation and providing anti-rust properties, as well as improving the coating's function and current efficiency, and making the appearance uniform.

The amount added is 10 to 90 f/l as Zn2+ and 44 to 400 f/l as zinc sulfate (Zn5Oa-7H20).
/l, preferably Zn'' 20 to 60 t/l.

That is, if it is too low, it will be dominated by the generation of hydrogen gas, and if it is too high, it will be difficult to color.

Next, the colored metal ion Me''+ will be described.

In the present invention, a black film can be obtained with a considerable amount of metal ions, among which N, 2+, Co2+, Fe2
+.

Fe3+, Or3+, Sn2+, and Cu2+ are suitable for obtaining black color. Concentration is 10-100 as Men+
At f/l, the lance with Zn2+ is Men+/Zn
2+weight ratio is 1 or more.

The most desirable range is 1.5 to 8.0. If a groove without a groove is coated with a highly acidic chromate treatment or a resin containing carzexyl, discoloration and poor adhesion are likely to occur. Also, Zn2
If + is not present, the degree of coloring is low and tends to become uneven.

As the supply of Zn'', Men+, sulfuric acid ring, chloride,
Phosphates and sulfonates, and carbonates, oxides, hydroxides, metal powders, etc. can be used as supplements.

OX is NO3-, NO2-, 0104-, 0LO5'-
An ion selected from the following, supplied as a soluble salt or acid.

The appropriate concentration of ions is 1 to 50 t/l.

If it is less than 1 f/, sufficient oxide is not formed and no coloring occurs. Moreover, if it exceeds 50 f/, coloring becomes difficult due to the generation of gas, and unevenness tends to occur.

The preferred OX concentration for obtaining black color is 2 to 10 f/rc.

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. If the pH is less than 1, it will become uneven due to the generation of hydrogen gas. Moreover, if it exceeds 4, precipitation tends to occur. pH from the viewpoint of powdering, adhesion with guard coat, etc.
1 to 2 are preferred.

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 Zn2+.

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

As the brightening agent, water-soluble polymer compounds such as cationic quaternary ammonium salt polyamine polymers, polyamine sulfone polymer compounds, nonionic polyacrylamide compounds, and combinations of these with anionic compounds are used. Polymers, aldehydes, phenolic compounds, and sulfonic acid compounds known as known brighteners can be used.

The amount added varies depending on the type of compound, and is 10 to 40,000
Add as appropriate within the ppm range.

The electrolysis conditions will be described below.

The present invention is an extremely superior method that allows selection of a wider range of conditions for coloring than conventional methods. Current density is 5-100
A/dW? shall be. If it is less than 5 A/d-, coloring is difficult. Moreover, if it exceeds 100 A/d-, hydrogen gas will be generated, and there is a high risk that the formed film will come off. The amount of current applied is 20 to 200 coulombs/d-. If it is less than 20 coulombs/d-, coloring is difficult and tends to result in an uneven appearance. Moreover, if it exceeds 200 coulombs/d-, film removal and pinhole damage due to hydrogen gas are likely to occur.

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

High flow rates and high current densities are preferred.

The surfaces to be treated were cold-rolled steel sheets, zinc alloy-plated steel sheets, galvanized steel sheets, bright galvanized steel sheets, tin-plated steel sheets, etc. As a result, all of them were colored, and in the case of black, cold-rolled steel sheets and zinc alloy-plated steel sheets were black. It is 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 7-talates as pH9 buffering agents, polymers to improve adhesion processability, and rust prevention and adhesive strength with guard coats. phosphate and chromic acid,
These include 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 the well-known roll coating, roll squeezing, spray coating, air knife squeezing, dipping, electrolytic treatment, and electrostatic coating, followed by heating (hot air, infrared rays, Combustion furnace, electric heating) or ultraviolet curing can be used.

(Example) Examples are given below.

Unless otherwise specified, Zn2+ and Men+ were prepared from sulfate, and OX was prepared using sodium salt.

The electric density is indicated as Dk, and the unit is A/I-. t1
1 is denoted by Q, and the unit is coulomb/d-. The amount of colored coating applied is expressed in CW, measured gravimetrically and expressed in f/d.

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.

For Examples without particular explanation, the following chemical conversion treatment and Go 1 coating were performed.

The chromate was a composite chromate consisting of silica and chromic acid, which was attached as Or20, and the N-p coat was a clear coating film of a commercially available water-based olefin acrylic acid emulsion and silica sol. Roll coating was applied with a film thickness of approximately 1 μm as the target value, and baking was performed with hot air aiming at a board temperature of 120°C.

Among the quality, adhesion was determined by visual inspection after the tape was peeled off after 180 degree bending of the T-curve (IT). evaluated.

Corrosion resistance was tested using a continuous method of salt spray test according to JI8Z 2371 standard, and was expressed as the time required to generate 5 squares of rust in terms of area ratio.

Example 1 A cold-rolled steel sheet was subjected to electrolytic zinc-nickel alloy plating (Ni12T) for 20 f from a sulfuric acid bath using a known method, and then subjected to the color coating treatment shown in Table 1, followed by chromate treatment. Painted guard coat.

In flat 1, Men+ is combined with Ni2+ and Me/Zn =
In the example of 1.47, IL2-6 are Me'+ and Ni2+
and Fe2+. This is an example in which the pH of only House 6 was 2.5, which was higher than the others. In all cases, black appearance was obtained and practical quality was obtained. Among these composite additive baths, the one with a low pH exhibited the best adhesion.

n+ Grave 7 is an example where Me is Fe, Ya 8 and 9 are N; 2
+.

This is an example of a composite addition bath of 2+ Co and Fe'', Or'+.

410 is an example of a bath in which Me"+ is not added, and the blackness is insufficient and the adhesion is poor. In No. 11, the Ni2+/Zn2+ ratio is 0.
．． Examples with a low value of 67 indicate insufficient L value and adhesion.

A12 to 15 were obtained by changing the type of OX, NO3- had the lowest L value, and other oxidizing ions also had a blackening effect.

A 16 and 17 are Fe, 8n2+, Ou2+
Composite additive 2+ with Me
The influence of the 'vZn2+ ratio was investigated, and if Zn2'' was too low, there was a tendency for non-uniform appearance.

A21 is an example of a Zn2+ additive-free bath, has a high L value, and exhibits a non-uniform appearance due to gas.

Example 2 Zn” 45 f/L, Ni2+44 t/L, F
e2+43 f/L.

(Me”/Zn”= 1.93) NaNOs 5
? /L pH = 1.4 aqueous solution g, using a lead plate as an anode, various steel plates and plated steel plates shown in Table 2 were subjected to cathodic electrolysis (20 A/dm' s O coulomb/dm')
After that, chromate treatment and guard coating were applied and baked.

This treatment method does not depend on the metal to be treated and can color steel sheets and plated steel sheets.

Example 3 12% N using the acidic aqueous solution and electrolytic conditions of Example 2
i-Zn alloy plated steel plate (fabric weight 20t/n?) After blackening, 0rbs/304 = 20/0.
15 f/L< Bathing), 0r03/H3PO
4-20/ 0.15 t/L (bath B) of cathodic electrolytic chromate treatment (3 A/dm" 10
Coulomb/d-), a commercially available composite paint of polyethyleneimine acrylic acid emulsion and silica sol was applied in a dry coating film of 1 μm and baked at 120°C.

Regarding the blackness, the L value was 12 in the bath and 11 in the B bath, and the adhesion was 11 in both cases, with no peeling observed.

Example 4 Cold rolled steel plate with average roughness Ra) of 0.6, 1.2, 2
．． After 0μ bright and dull finish rolling, pretreatment and 12% Ni-Zn alloy plating (fabric weight 2
0 f/rp? ) and the blackening treatment of Example 3, and then the chromate and guard coat of Example 1 (thickness: 1
．． 5μ) was performed. For those with an average roughness of 1.2μ, the thickness of the guard coat was 2.3.5μ.

The results are shown in Table 3.

Table 3 Also, when spot welding was attempted using a conventional and known method, current conduction failure began to occur when the guard coat thickness was around 3 μm, and welding could not be performed at 5 μm.

Example 5 The same treatment as in Example 2 was carried out using Solution A, which was obtained by adding SOOOppm of a commercially available polyamine sulfone polymer to the acidic aqueous solution used in Example 2, and Solution B, which was obtained by adding 201) pm of polyacrylamide to the acidic aqueous solution used in Example 2. I went to Zn electroplated steel sheet.

L value is A=11. A black plate with excellent adhesion was obtained.

(Effects of the Invention) The colored zinc composite plated steel sheet according to the present invention has a high quality appearance and
As a new steel sheet with excellent workability, corrosion resistance, and strong resistance to scratches, it can be used in the field of conventional coated steel sheets, contributing to higher quality products and lower costs.

In addition, since a very wide range of processing conditions can be applied in terms of manufacturing, and high-speed, 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 the drawing]

FIG. 1 is a diagram showing the coloring mechanism of the present invention and the structure of its coating, and Figure 2 (al + fb) is a diagram showing the structure of the colored zinc composite plated upper plate of the present invention. Agent Patent attorney Masamitsu Akizawa and 1 other person F1 Figure 2 Figure CQ) (b)

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 indicated by Zn^2^+ and Me^n^+ and strongly oxidizing ions indicated by OX. The amount of adhesion obtained is 0.1 to 5 g/m^
1. A colored coated steel sheet having a coating mainly composed of the colored oxide of No. 2, and further having a chemical conversion treatment and a guard coat of 3μ or less on the coating. (2) Me^n^+ in acidic aqueous solution is 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_
The colored coated steel sheet according to claim 1, which is any one of 3^2^-. (3) The colored coated steel sheet according to claim 1, wherein the steel sheet or plated steel sheet is made of a bright finished material having an average roughness of 1.0 μm or less or a dull finish material having an average roughness of 1.5 μm or more. (4) Zn^2^+ is 10 to 90 g/l, Me^n^+
is 10 to 100 g/l and Me^n^+/Zn^2^
In an acidic aqueous solution with a pH of 1 to 4 containing OX^- as a main component with a + ratio of 1 or more and a current density of 5 to 100 A/dm^2 using a steel plate or plated steel plate as a cathode,
A method for producing a colored coated steel sheet, comprising electrolytic treatment at 200 coulombs/dm^2, washing with water, chemical conversion treatment, and subsequent coating with a guard coat of 3μ or less. (5) Me^n^+ is Ni^2^+, Co^2^+, F
e^2^+, Fe^3^+, Cr^3^+, Sn^2^
+, Cu^2^+ one or more OX is NO_3^-, NO
_2, ClO_4^-, ClO_3^2^-, the method according to claim 4.