JPS61291981A - Manufacture of black zinc alloy plated steel sheet - Google Patents

Abstract

PURPOSE:To uniformly blacken a Zn alloy plated steel sheet at a high speed in a short time by anodizing the steel sheet in an acidic aqueous soln. contg. nitrate and phosphate ions in a specified molar ratio. CONSTITUTION:A steel sheet plated with a Zn alloy contg. a blackening metal such as a Zn-Ni alloy is anodized in an acidic aqueous soln. contg. nitrate and phosphate ions. The molar ratio of the nitrate/phosphate ions in the electrolytic soln. is 0.01-1.5 and the pH of the soln. is <=3.0. One or more among chromic acid, vanadic acid, molbdic acid, permanganic acid and peroxide are preferably added to the electrolytic soln. by 0.001-1%. By this method, a blackened Zn alloy plated steel sheet having superior solvent and scratch resistances is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention generally relates to a method for manufacturing a black galvanized steel sheet for use in members requiring decoration in fields where galvanized steel sheets are used.

(Conventional Technology J) Low-cost, high-performance quality has been consistently required for steel sheets used in the fields of rust-proofing automobiles, home appliances, furniture, and building materials.9 In response to these demands, Steel manufacturers continue to develop new technologies and products to meet customer demands.

Recently, pre-coated steel sheets have been introduced for products that have conventionally been processed using surface-treated steel sheets and then pre-treated and painted, thereby eliminating the pre-treatment and painting that were performed in the customer process and reducing costs. There is an active movement toward the use of pre-painted steel sheets to obtain high-quality products.High-grade pre-painted steel sheets with a thickness of 20 to 30μ have been used for the first time as pre-painted steel sheets that can meet these demands. Colored surface-treated steel sheets are desired from the viewpoint of pursuit and weldability.

The qualities that materials should have to meet these demands are:
In addition to corrosion resistance and workability, uniformity of appearance is important, and weldability and chemical resistance are required as necessary. A known coloring process for galvanized steel sheets, in which a black color tone is preferred, is disclosed in JP-A-52-45544, in which galvanization is treated in a chromate solution containing silver ions. There is a method disclosed in JP-A-58-177477 which involves treatment in a chromate solution containing phosphoric acid and silver phosphate as a paste. These methods eutectoid silver oxide on a chromate film to obtain a black appearance. Furthermore, as a method for forming sulfides and performing blackening treatment, a method disclosed in Japanese Patent Application Laid-Open No. 52-65139 is known. Furthermore, as a method of coloring the chromate film using a dye after forming it, the methods disclosed in Japanese Patent Application Laid-open No. 145336/1982 and Japanese Patent Publication No. 28730/1982 are known. All of these methods involve a direct chemical reaction between a solution and galvanizing to obtain a colored surface. In addition, a method of obtaining a black surface by an explicit oxidation method is known. For example, Nl
.

Oo, JP 58-151491 Anodic treatment of Mo and Zn alloy plated steel sheet in ammonium sulfate aqueous solution
The method disclosed in JP-A-58-151490 involves anodizing in an alloy plating bath of Ni, Oo, Mo and Zn.
The method disclosed in the above publication is a typical technique.

(Problems to be solved by the invention) The conventional coloring method is an excellent method, but unfortunately there are some points in which it does not necessarily match the manufacturing equipment owned by steel manufacturers.For example, in terms of high-speed productivity. It is necessary to complete uniform coloring in a shorter time.In addition, it is a chemical conversion treatment technology that has never been experienced before to stably obtain large quantities of wide coil products with a uniformly colored appearance.

The present invention provides a method for coloring galvanized products with uniform color tone at high speed and in a short time.

(Ninth means and action for solving the problem) The present invention has the following four features.
It can be summarized in one method.

(b) A steel plate coated with an alloy of zinc and a metal that turns black, containing nitrate ions and phosphate ions, with a molar ratio of phosphate ions/nitrate ions of 0.01 to 1.5, and a pH of 3.0 or less. A method for producing a black zinc alloy plated steel sheet, characterized by chemical treatment with an acidic aqueous solution.

(b) A steel plate plated with an alloy of zinc and a metal that turns black is mixed with chromic acid and vanadium in an aqueous solution containing nitrate ions, sulfur ions, and a phosphate ion/nitrate ion molar ratio of 0.01 to 1.5. pH = 3.0 containing o, o o t to 1 or more of acid, molybdic acid, permanganic acid, peroxide
A method for producing a black zinc alloy plated steel sheet, characterized by chemical treatment with the following acidic aqueous solution.

e→ A steel plate plated with an alloy of zinc and a metal that turns black is acidic, containing nitrate ions and phosphate ions, with a molar ratio of phosphate ions/nitrate ions of 0.01 to 1.5, and a pH of 3.0 or less. A method for manufacturing a black zinc alloy plated steel sheet, which comprises chemically treating it with an aqueous solution and then coating it with a protective film.

2) A steel plate plated with an alloy of zinc and a metal that turns black is added to an aqueous solution containing nitrate ions and phosphate ions and having a molar ratio of phosphate ions to nitrate ions of 0.01 to 1.5 with chromic acid,
It is characterized by coating with a protective film after chemical treatment with an acidic aqueous solution with a pH of 3.0 or less containing o, o o t to 1 h gamma of one or more of vanadate, molybdic acid, permanganic acid, and peroxide. A method for manufacturing a black zinc alloy plated steel sheet.

In each of the above methods, the metal to be blackened is preferably a metal containing one or more of nickel, cobalt, iron, copper, chromium, molybdenum, and tin.

The present invention uses zinc, which has excellent corrosion resistance, and a blackening metal (hereinafter referred to as M).
By chemically treating the surface of the alloy-plated steel sheet with an oxidizing acidic aqueous solution, the passivated oxide of Me is fixed to the plating surface, resulting in a black-plated steel sheet with extremely high productivity. It's a method. The chemical treatment in the present invention refers to the following.

1. Dissolve the surface layer of the plating to make it shiny (
Polishing action].

2. Dissolved zinc is dissolved in the bath as ions, and Me
is immediately oxidized and adheres to the plating surface as %Me oxide.
Concentrate (oxidizing effect).

3. It is a one-bath method that does not generate precipitates in the treatment bath and has a uniform dissolution rate.

That is, the present invention is a chemical treatment method that balances the dissolution and oxidation of the chemical polishing action, which efficiently oxidizes 'Ae, and makes it into a passivated oxide, which remains on the plating surface.

Specific methods for chemical treatment include immersion in which the alloy-plated steel plate is brought into contact with the treatment bath, spraying for acceleration and uniformity, electrolysis using the alloy-plated steel plate as an anode, or a combination of these methods. By adopting one of these methods, it is possible to deal with the various line configurations of steel manufacturers. In any case, in order to uniformly blacken a wide plated steel plate, it is necessary to apply chemical treatment uniformly, and it is necessary to adopt an optimal treatment method that suits Reich's characteristics.

FIG. 1 schematically shows the principle of the present invention for a zinc and nickel alloy plated steel sheet. Figure 1(a) shows zinc-nickel alloy plating (indicated by 0). Through the chemical treatment of the present invention, the surface of the zinc-nickel alloy plating dissolves as shown in Figure 1(b), and zinc ions (○ ) is dissolved in the bath, and nickel or nickel ions chemically bond with oxygen and some phosphate ions (denoted by ) in the bath. A film containing salt (indicated as nickel oxide) is formed and adheres to the plating surface.
) In the reaction process, the plating surface is smoothed by chemical polishing or electrolytic polishing. FIG. 1(C) shows the state of the hole after chemical treatment. The plated surface is smoothed and has a black appearance due to nickel oxide and phosphate.

Method (a) includes nitrate ions and phosphate ions, and the molar ratio of phosphate ions/nitrate ions is 0.01 to 1.5.
This is a method of chemically treating zinc alloy plating using an acidic aqueous solution with a pH of 3 or less.

The pH setting was excluded from the present invention because if it exceeds pH 3, phosphoric acid will be included in the black film and precipitation will occur in the aqueous solution, which will have an adverse effect on the appearance. The desired pH of the aqueous solution is related to the method of chemical treatment. According to experiments conducted by the present inventors, as a chemical treatment method, the liquid flow rate is 1 at room temperature.
When immersed in an aqueous solution of about m 7 min, a desirable pH range was 0.5 to 1.5 to obtain a truly black appearance. Also, in the case of spraying, a similar black appearance was obtained in the range of p).

In the method of electrolytic treatment with an anode as a chemical treatment, b9
A truly black appearance was obtained in the range below H3, but at pH below 1 there is no difference from the method using dipping or spraying, and the merit of anodizing is small. Therefore, according to the experiments conducted by the present inventors, pi-it~3 is a desirable range in the anodic treatment method.

The concentration of nitrate ions affects both dissolution and oxidation of the alloy plating, and is set based on the desired color tone, line characteristics, and alloy plating composition. If the nitrate ion content is too low, hydrogen gas will be generated from the alloy plating surface and a beautiful appearance may not be obtained.
HepH Nakaru.

In the present invention, it is desirable that the insolubilization efficiency (hereinafter referred to as coloring efficiency) based on the oxidation of the blackened metal with respect to the dissolution of the alloy plating in the chemical treatment is high, and this can be summarized as shown in Figure 2. , low nitrate ion concentration and pH
In a treatment solution with a low oxidation rate, the rate of dissolution and oxidation is poor, as shown in B in Figure 2.

On the other hand, people whose dissolution and oxidation occur evenly and smoothly tend to have a beautiful appearance. 0 in FIG. 2 has the best coloring efficiency, but chemical reactions tend to occur unevenly and tend to become uneven. Factors that affect the second strong x axis (oxidation effect) are the concentration of nitrate ions and the Me concentration in the alloy plating. On the other hand, on the Y axis (dissolution J).

Lowering the phosphate ion concentration and pH is effective.

In the present invention, it is desirable to use conditions that allow uniform dissolution with a coloring efficiency as close to the conditions shown in FIG. 2C as possible.

Phosphate ions are added for the purpose of dissolving the alloy plating into a smooth, glossy polished surface and obtaining a uniformly colored appearance. The first and second phosphorus ions.

In addition to tertiary phosphate ions, condensed phosphate ions of pyrophosphoric acid and polyphosphoric acid are also effective. The amount of acid ions added is 0.60 molar ratio of phosphate ion / nitrate ion.
It is in the range of 1 to 1.5. If the molar ratio exceeds 1.5, the coloring efficiency as shown in k in FIG. 2 will be low, the amount of phosphate incorporated into the film will increase, and the appearance will likely become white and uneven. or,
If it is less than 0.01, the polishing effect will be too weak, resulting in a matte and uneven appearance, and the resulting black film will easily peel off into powder (also called powdering). There are other organic acids that exhibit similar effects.

Method (b) is a coloring treatment method using a bath in which additives are added to the bath of (a) to strengthen the smoothing action and oxidation action, to obtain a glossy colored appearance, and to further improve corrosion resistance.

Additives include chromate ion, vanadate ion,
Molybdate ions, perma/ganate ions, or peroxides that provide active generators of oxygen, such as H, O, Na2O. The amount of these compounds added has a great influence on the blackening pressure, with concentrations ranging from o, o ot to 1. O
i is preferably 0.01 to 0.1 h. The reason for this is that if the additive content is less than 0.0011%, no clear effect will be observed, and if it exceeds 1.0%, the blackness will decrease or the appearance will take on a reddish color. be.

Methods (c) and 2) form a protective film on the colored film obtained in (a) and (b), and improve the degree of coloring, gloss, and uniformity.
It aims to improve the appearance such as corrosion, act as a guard coat against scratches, and improve corrosion resistance. The method for treating the protective film will be described below.

The protective film includes an inorganic film, an organic film, a composite film of both, or a chemical conversion film.

Inorganic coatings include silicate, phosphate, zirconate coatings, and titanium compound coatings, and organic coating is a method in which a water-soluble or water-dispersible organic polymer compound is coated together with a curing agent. In addition, there are baths that are a combination of organic and inorganic substances, such as a bath that is a combination of organic polymer compounds and silica. Further, chemical conversion coatings include chromate-treated coatings, phosphate-treated coatings, chelate-treated coatings, tannic acid-treated coatings, phytic acid-treated coatings, and silane-treated coatings. Of course, by combining chemical conversion coating components with organic polymers and inorganic coatings, or by stacking two or more layers, a protective coating with further improved corrosion resistance, workability, appearance, etc. can be obtained.

Methods for coating the protective film include coating by rolling, spraying, or electrolytic treatment, and then baking. The coating method and baking conditions vary depending on the type, composition, and line characteristics of the protective film. According to experiments conducted by the present inventors, a method of performing coloring treatment, chromate treatment, and then guard coating with an organic and inorganic composite film can be proposed as a desirable method.

In the present invention, the conditions for the metal to be blackened (hereinafter referred to as 'Je5) are: 1) the metal should oxidize and become black, 2) it should remain on the plating surface at an electrochemically nobler potential than zinc, and 2) it should be sufficient. The point is that a suitable alloy composition can be obtained. TJe is a metal or composite alloy of one or more of nickel, cobalt, iron, copper, chromium, molybdenum, and tin.

The composition of the zinc-Me alloy plated steel sheet used in the present invention varies depending on the desired appearance (that is, the depth of blackness) and line configuration. An example of achieving a true black appearance is Me or M.
If there are two or more types of e, the total amount is 1 in the alloy plated steel plate.
Alloy plating with zinc containing ~50% is desirable. When the amount of chemical treatment (the amount of reaction of the alloy on the treatment bath) is constant, the degree of blackness is strong compared to the Me content, ρ, and the steel plate coated with a high Me content alloy (for the purpose of blackening) Time can be shortened.

The degree of blackening is determined by the needs of the user, and a chemical processing amount of 2 alloy plating composition can meet those needs.

In the present invention, as a method for improving the appearance, it is also possible to use a bright alloy-plated steel sheet that is electroplated from a subsequent plating bath with the addition of a brightening agent. As the brightening agent, a plating bath containing a known brightening agent such as quaternary amino/polymer, polyacrylamide P, or dextrif may be used.

(Example 1) After plating a steel plate with zinc-nickel alloy plating containing Ni (12±1%) (plating amount 20 P/m'), 1
The plated steel plate was immersed in the coloring treatment bath shown in Table 1 or subjected to electrolytic treatment using the stainless steel plate as the anode and the cathode, followed by washing with water and drying to obtain a black appearance.

The processing steps are as follows.

Alloy plating → water washing → coloring treatment → water washing → drying Table 1 shows the concentrations of nitrate ions and phosphate ions and PO4/NO of the present invention.
3 shows the quality when electrolysis and immersion were performed as treatment baths and treatment methods with different ratios and I)H. Comparative Example 1 is an example in which nitrate ion is used alone, and the luster is insufficient and smearing easily occurs.

Examples 3.4 and 5.6 of the present invention are examples of baths containing high concentrations of nitrate ions. 1, 7, 8, and 9 are baths using nitric acid as a nitric acid ion source, and 1O, 11, 12, and 13° are examples in which the concentration of PO4 relative to NO3- was varied. Comparative example 2.3
The ratio of phosphate ions to nitrate ions is out of proportion.

In addition, the evaluation of blackness, workability, and corrosion resistance is as follows.

Blackness @: Black specular appearance L value 12 or less ◎: Black gloss appearance L value 12 or less ○: Slightly (f black, entry point) Li 115 or less: Blueish or gray appearance L value 20 or less Gloss ◎: 60° As black glass T-94 with gloss meter.

20 or more O: 15-20 Δ: l 10-15×
: Workability: 5 or less: Tape the convex part after squeezing with Erichsen for 7 minutes, and evaluate by peeling it ◎: No peeling ○: The base material does not peel off, but powder adheres to the tape Δ: IOX on the processed part peels off ×: 20% or more peeling of the processed part Corrosion resistance... Time for 5% white rust to occur in salt spray test (JI8Z2371) ◎: 168 hours or more O: 72 to 168 hours 6224 to 72 hours ×: 24 hours or less (Example 2) H4 containing Ni s*io-z os 40
-Zn alloy plated steel plate with HNOs l 5 f /ls
I' Aqueous solution of H=0-8 (A) h NaNO
s l 00 f/l -Hs PO420t/L
(% ratio 0.18), blackening treatment was performed with an aqueous solution (B) of I)H=2.0. In the case of liquid A, spray treatment was performed. 50A/dtr at the anode for B liquid? electrolytically treated. Immediately after treatment, they were washed with water and dried. The results are shown in Table 2.

Table 2 shows the black appearance, workability, and corrosion resistance when the Ni content in the alloy plating was changed from 5 to 4X in the present invention.
Samples 8 to 21 were electrolytically treated. Comparative Example 4.5 uses a commercially available Tetsujin chromate treatment method, which requires a long time of 120 seconds to obtain a black appearance different from the present invention, which is the result of treatment by spraying using a bath.

(Example 3) Table 3 shows N1-z n alloy plated steel sheets containing NilZ±1%.
It was blackened using the treatment bath shown in . The results are shown in Table 3. In all cases, the blackness was good and the effect of improving corrosion resistance was observed.Inventive Examples 22 to 26 used chromic anhydride, vanadic acid, and molybdic acid in a nitric acid and phosphoric acid bath.

The results were treated by a spray method using a bath containing sodium permanganate, and Examples 27 to 31 of the present invention were treated by electrolysis.

(Example 4) Polyamine sulfone 0.5 as brightener? A bright Nj-zn alloy metal steel plate obtained from a NiΔzn alloy plating bath prepared to contain 1% Ni with 12% of NaNOa /Hs P 04 = 80 / 7
f/ L O-bi NakjOs /H3PO410rb
s = 80/ 710.1 t/l I) H = 0.8
The specimens were immersed in an aqueous solution, subjected to a blackening treatment, washed with water, dried, and evaluated. The appearance was a glossy black appearance, and especially the gloss of the bath placed in 0rOs7 was good. ＠It has good wearability and corrosion resistance, with white rust forming in 48 hours.

(Example 5) A Hl-zn alloy plated steel plate containing Nixz±1% was subjected to the blackening treatment of Example 4, thoroughly washed with water, and then coated with the protective film shown in Table 4.

The protective film was applied by roll coating an aqueous solution and baked with hot air to a board temperature of 120°C. Inventive Example 32.33 is an organic (32
) and an organic-inorganic polymer system (33). 34.35 is an example of chromate treatment, 36.38 is inorganic rust prevention treatment% 37 is complete inorganic treatment, 0 quality is almost generally good.9.

Composition of protective film A: Aqueous dispersion of 10% acrylic ester emulsion and 1% water-soluble melamine B: 10% polyethyleneimine emulsion, 5% colloidal silica, and o and i% silane coupling agents. Aqueous dispersion 0...Aqueous solution of ammonium polyacrylate 10%, ammonium dichromate 2X%, colloidal silica 1% F...Aqueous solution of ammonium zirconate 10% and polyacrylic acid 1% G... Condensed phosphorus 5% aqueous solution of magnesium salt of acid (Example 6) The alloy plated steel sheet shown in Table 5 was treated with N'lNOs/H3
PO410rbs=100/3010.02t/l,
After spraying a pH=0.8O aqueous solution for 5 seconds to blacken the surface.

SiO! / Or Os = 415 Baked at °C. The results are shown in Table 5.

Inventive Example 39 in Table 5 shows the coloring effect of a ternary alloy film obtained by adding 00 to Nin alloy plating. Inside, it was sprayed black. Both appearance and corrosion resistance were good.

(Effects of the invention) According to the present invention, a highly productive colored plated steel sheet can be obtained.
1.Coloring, which can provide low-cost surface-treated steel sheets without reducing quality, has traditionally been provided by paints, but
In the present invention, it is composed of a thin inorganic film, which has solvent resistance,
It has the advantage of being highly scratch resistant and not discolored. In particular, when a protective film is applied, a transparent black appearance can be obtained, and a color tone effect that cannot be obtained with conventional paints can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the reaction process of the present invention. (a) shows alloy plating, (b) shows the reaction in a coloring treatment bath, and (0) is a cross-sectional configuration diagram after coloring treatment. Figure 2 shows the relationship between melting and oxidation of alloy plating. Agent Patent Attorney Masamitsu Akizawa et al. 1 Figure Note 2 → Nishizune I B Voluntary Proceedings Amendment September 16, 1986

Claims (8)

[Claims] (1) A steel plate coated with an alloy of zinc and a metal that turns black, containing nitrate ions and phosphate ions, with a molar ratio of phosphate ions/nitrate ions of 0.01 to 1.5, and a pH of 3.0 or less. A method for producing a black zinc alloy plated steel sheet, characterized by chemical treatment with an acidic aqueous solution. (2) The metals that turn black are nickel, cobalt, iron, copper,
The method for producing a black zinc alloy plated steel sheet according to claim 1, wherein the metal is a metal containing one or more of chromium, molybdenum, and tin. (3) Add chromic acid and vanadate to an aqueous solution containing zinc and a blackening metal alloy plated steel plate, which contains nitrate ions and phosphate ions, and has a molar ratio of phosphate ions to nitrate ions of 0.01 to 1.5. A method for producing a black zinc alloy plated steel sheet, comprising chemically treating it with an acidic aqueous solution having a pH of 3.0 or less and containing 0.001 to 1% of one or more of molybdic acid, permanganic acid, and peroxide. (4) The metals that turn black are nickel, cobalt, iron, copper,
The method for manufacturing a black zinc alloy plated steel sheet according to claim 3, wherein the metal is a metal containing one or more of chromium, molybdenum, and tin. (5) A steel plate plated with an alloy of zinc and a metal that turns black, containing nitrate ions and phosphate ions, with a molar ratio of phosphate ions/nitrate ions of 0.01 to 1.5, and a pH of 3.0 or less. A method for manufacturing a black zinc alloy plated steel sheet, which comprises chemically treating it with an acidic aqueous solution and then coating it with a protective film. (6) The metals that turn black are nickel, cobalt, iron, copper,
The method for manufacturing a black zinc alloy plated steel sheet according to claim 5, wherein the metal is a metal containing one or more of chromium, molybdenum, and tin. (7) Add chromic acid and vanadate to an aqueous solution containing zinc and a blackening metal alloy plated steel plate, which contains nitrate ions and phosphate ions and has a molar ratio of phosphate ions to nitrate ions of 0.01 to 1.5. A black zinc alloy is coated with a protective film after being chemically treated with an acidic aqueous solution containing 0.001 to 1% of one or more of molybdic acid, permanganic acid, and peroxide and having a pH of 3.0 or less. Method for manufacturing gold-plated steel sheets. (8) The metals that turn black are nickel, cobalt, iron, copper,
The method for manufacturing a black zinc alloy plated steel sheet according to claim 7, wherein the metal is a metal containing one or more of chromium, molybdenum, and tin.