JPS6270583A - Production of black zinc alloy plated steel sheet - Google Patents

Abstract

PURPOSE:To quickly and easily produce a black zinc alloy plated steel sheet having a uniform color tone by subjecting the steel sheet plated with an alloy consisting of zinc and metals which blacken to a spraying or immersion treatment in an acidic aq. soln. consisting of a specifically composed nitrate and phosphoric acid. CONSTITUTION:The steel sheet plated with the alloy consisting of the zinc and >=1 kinds of the metals such as nickel, cobalt, iron, copper, chromium, molybdenum and tin which blacken is subjected to the spraying treatment or immersion treatment in the aq. acidic soln. having 0.01-1.5mol ratio of the phosphoric acid/nitrate and <=1.5pH. The passivated oxide of the above- mentioned metals which blacken is thereby fixed onto the plating surface and the black plated steel sheet is obtd. The brightness and corrosion resistance of the plating surface are improved by adding 0.01-1.0% >=1 kinds among chromic acid, vanadic acid, molybdic acid and peroxide to the above-mentioned soln. The appearance, scratch resistance, etc. are preferably improved by coating a protective film on the plating surface.

Description

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

(Prior Art) Low-cost, high-performance quality has always been required for rust-proof steel plates for cutting wheels, and steel plates used in the fields of home appliances, furniture, and building materials. In response to these demands, steel manufacturers developed new technologies and products to meet the demands of customers.

Recently, for products that were conventionally surface-treated steel sheets (i-processed and then pre-treated and painted), by introducing ZOLE-coated steel sheets, the pre-treatment and painting that were performed in the customer process can be omitted, resulting in lower costs. There is a strong movement toward the use of Brecoat steel sheets to obtain high-quality products.

Initially, 2 was developed as a Brecoat steel sheet that could meet these demands.
High-grade Brecoat steel plates of 0 to 30μ have been used,
Colored surface-treated steel sheets are desired from the viewpoints of thorough cost reduction 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. Black-ish colors are preferred.

Known techniques for blackening galvanized steel sheets include a method disclosed in Japanese Patent Application Laid-Open No. 52-45544 in which zinc plating is treated in a chromate a solution containing silver ions, and a method based on phosphoric acid and silver phosphate. There is a method disclosed in Japanese Patent Application Laid-Open No. 177477/1983, which involves treatment in a chromate solution. 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, the method disclosed in JP-A-52-65139 is mentioned. Furthermore, as a method for coloring the chromate film using a dye after forming it, the methods disclosed in Japanese Patent Application Laid-open No. 145336/1982 and No. 28730/1988 are mentioned. All of these methods involve a direct chemical reaction between a solution and galvanizing to obtain a colored surface. In addition, there is a method of obtaining a black surface by anodizing. For example, Ni
, Co.

JP-A-58-151491 discloses a method of anodizing a Mo,:Zn alloy plated steel sheet in an ammonium sulfate aqueous solution; JP-A-58-151490 discloses anodizing a Ni, Co, Mo and Zn alloy plated steel sheet in an alloy plating bath of Ni, Co, Mo and Zn; The method described in the official gazette is a typical technique.

(Problems to be Solved by the Invention) Conventional coloring methods are excellent methods, but unfortunately they do 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 an unprecedented chemical conversion technology that can stably produce large amounts of wide coil products with a uniformly colored appearance.

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

(Means and effects for solving the problems) The present invention has the following two features.
It can be summarized in one method.

(a) Spray or spray a steel plate plated with an alloy of zinc and a blackening metal in an acidic aqueous solution composed of nitrate and phosphoric acid, with a molar ratio of phosphoric acid/nitrate of 01 to 1, 1 to 5 or less. A method for producing a black zinc alloy plated steel sheet, which comprises dipping treatment.

(b) A steel plate coated with an alloy of zinc and a metal that turns black is composed of nitrate and phosphoric acid, and the molar ratio of phosphoric acid/nitrate is 0.
．． 1. A method for producing a black zinc alloy plated steel sheet, which comprises spraying or dipping the steel sheet in an acidic aqueous solution having a pH of 0.01 to 1.5 or less and coating it with a preservation film.

In the method (a) above, (c) the metal to be blackened is nickel, cobalt, iron, copper, chromium, or molybdenum.

It is a metal containing one or more of tin, and one or more of chromic acid, vanadate, molybdic acid, and peroxide.
It is preferable to use an aqueous solution containing ~1.0%.

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 (expressed as e) with an oxidizing acidic aqueous solution, the Me passivation oxide is fixed on the plating surface, and it has extremely high productivity to obtain a black-plated steel sheet. It's a method. The invention obtains a uniform and beautiful black surface by the following chemical action.

1. Dissolve the surface layer of the plating to make it shiny (
abrasive action).

2. Zinc decomposed into f6 is dissolved as ions in a bath, and M
Immediately oxidize e and cause solid N% to condense on the plating surface as Me oxide (oxidation action).

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

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

What are the specific chemical treatment methods used illegally?

There are immersion methods in which the alloy-plated steel sheet is exposed to a treatment bath, spraying methods for promoting and homogenization, and methods that combine these methods. It does not require expensive electrolysis equipment and can be applied to existing lines.

FIG. 1 schematically shows the principle of non-invention for zinc and nickel alloy plated steel sheets. FIG. 1(a) shows alloy plating of thrust nickel (indicated by ``)''. As shown in Figure 1(b), the chemical treatment of the present invention dissolves the surface of the zinc-nickel alloy plating, zinc ions (indicated by ○) dissolve in the bath, and nickel or nickel ions dissolve in the oxygen and nickel ions in the bath. It chemically bonds with some phosphate ions (these are indicated by m), forming a film containing phosphate (indicated by ) mainly composed of nickel oxide and fixed on the plating surface. In the reaction process shown in Figure 1 (bl), the plating surface is smoothed by chemical polishing. Figure 1 (c) shows the state after the chemical treatment. The plating surface is smoothed and nickel oxide and phosphorus are removed. A black appearance can be obtained due to the acid salt.

Method (a) is a method of blackening a zinc alloy plated steel plate by spraying or immersing it in an acidic aqueous solution consisting of nitrate and phosphoric acid with a phosphoric acid/nitrate molar ratio of 0.01 to 1.5 and a pH of 1.5 or less. It is.

If the pH is set above 1.5, it will take a long time to blacken, the black film will contain more phosphoric acid than necessary, and it will cause precipitation in the aqueous solution, which will have a negative impact on the appearance. I'm sorry for my lack of invention.

The desired pH of the aqueous solution is related to the method of chemical treatment.

According to experiments conducted by the present inventors, when immersion in an aqueous solution with a liquid flow rate of about 1rILZ- at room temperature is used as a chemical treatment method, a pH of 0.5 to 1.5 is desirable to obtain a truly black appearance. Ta. Also, in the case of spraying, a black appearance was obtained in the same pH range.

The concentration of nitrate affects both dissolution and oxidation of the 1st alloy plating, and is set based on the desired color tone and line characteristics 5th alloy plating composition. If the nitrate content is too low, hydrogen gas will be generated from the alloy plating surface, and a beautiful appearance may not be obtained. Therefore, the pH of the treatment bath should be set in consideration of the treatment method and alloy composition. In the black treatment of the present invention, it is desirable that the efficiency of indissolution based on oxidation of the metal to be blackened with respect to the dissolution of the alloy plating (hereinafter referred to as coloring efficiency) is high, and this can be summarized as shown in FIG. That is, nitrate @ is low and p
In a treatment solution with low H content, the balance between dissolution and oxidation is poor, as shown in B in FIG. On the other hand, A, in which dissolution and oxidation occur equally and in a well-balanced manner, tends to give a beautiful appearance. C in FIG. 2 has the best coloring efficiency, but the chemical reaction tends to occur unevenly and tends to be uneven. The X-axis of Figure 2 (
The factors that affect the oxidation effect are the concentration of nitrate, the concentration of salt, and the degree of Me@ in the alloy plating. -10,000, Y@I (6 solutions and polishing),
1L of phosphoric acid lowers the pH.

In the case of non-invention, it is desirable to use conditions that allow uniform dissolution with a black efficiency as close as possible to the conditions shown in Fig. 2C.

Phosphoric acid is an extremely effective acid for dissolving alloy plating to give it a smooth, glossy, polished surface and uniformly colored appearance; other acids hardly have this effect. A uniform black appearance cannot be obtained with sulfuric acid or hydrochloric acid. In addition to phosphoric acid, birophosphoric acid and condensed phosphoric acid of polyphosphoric acid are also effective. The amount of phosphoric acid added is such that the molar ratio of phosphoric acid/nitrate is in the range of 01 to 1.5.

If the molar ratio exceeds 1.5, the black efficiency as shown in A in Figure 2 is low;
The amount of phosphate seeped into the film increases, making the appearance more likely to become white and uneven. Also, below 'o, o i,
Since the polishing effect is too weak, it tends to have a matte and uneven appearance, and the resulting black film tends to peel off into powder (referred to as powdering).

The method (b) is a blackening method using a bath in which additives are added to the bath (a) to enhance the smoothing action and oxidation action to obtain a glossy black appearance, and to further improve corrosion resistance. Additives are chromate ions, vanadate ions, molybdenum modified ions, or peroxides 1.1 that supply active generator oxygen, such as H2O3, Nag 02. The amount of these compounds added has a great effect on blackening, and the concentration is from o, ooi to 1.0, preferably 0.01
~0.1%. The reason is that the content of additives is 0.0
If it is less than 0.01%, no clear effect will be observed, and if it exceeds 1.0%, the blackness will be lowered and the appearance will take on another color, such as a reddish tinge.

Method (b) is a method in which a protective film is formed on the black film obtained in (a) to improve appearance such as blackness, gloss, and uniformity, serve as a guard coat against scratches, and improve corrosion resistance. It is. 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 films include silicate, phosphate, zirconate films, titanium compound films, and organic films BIi//'i
This is a method of coating a water-bathable, water-dispersible organic polymer compound together with a curing agent. There are also baths that are a combination of organic and inorganic materials, such as a composite bath of an organic polymer compound 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, we can combine chemical conversion coating components with organic polymers and inorganic coatings.

By stacking two or more layers, a protective film with better corrosion resistance, workability, appearance, etc. can be obtained.

As a method of coating with a protective film, there is a method of coating with a roll, spray, or scrap 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 Me) are: (1) The metal must be oxidized and blackened.

■1 more than zinc! It remains on the plating surface at a vapor chemically stable potential, and it can obtain a light-sensitive alloy composition. Me
Nickel, Kobal), i, m.

It is a metal or composite alloy of one or more of 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. As an example of obtaining a true black appearance, if Me or two or more layers of Me are present, alloy plating with zinc containing 1 to 50% of the total amount in the alloy plated steel sheet is desirable. When the amount of chemical treatment (the amount of reaction between the treatment bath and the alloy) is constant, the degree of blackness increases in proportion to the Me content, and the time (for blackening) for coated steel sheets with high Me content decreases. It can be timed.

The degree of blackening is determined by the needs of the laser, and a chemical throughput of 1 alloy plating composition can meet those needs.

In the present invention, as a method for achieving the same appearance as described above, it is also possible to use a bright alloy-plated steel sheet electroplated from a plating bath to which a brightening agent has been added. As the brightening agent, a plating bath containing a known brightening agent such as a quaternary amine polymer, polyacrylamide, or dextrif may be used.

Hereinafter, non-inventive embodiments will be described. The molar ratio in the examples means the phosphoric acid/nitrate molar ratio.

Evaluations of blackness, workability, and corrosion resistance are as follows.

Blackness @: Black specular appearance L value 12 or less ◎: Black glossy appearance L value 12 or less O: Slightly (blue-black, gray-black) L value 15 or less Δ: Evening or gray appearance
L value 2o or less Gloss ◎: Black glass is 94 with a 600 gloss meter, 20 or more ○: Black glass is 94 with a 600 gloss meter, 15
~20Δ: lO~15×:
Workability: 5 or less Processability: After squeezing 7fi with Erichsen, tape the convex part and evaluate by peeling ◎: No peeling ○: Substrate does not peel off, but powder adheres to the tape Δ: 10% of processed area peels off : 20% or more peeling corrosion resistance on the processed part...Time when 5% white rust occurred in salt spray test (JIS Z2371) 02168 hours or more ○: 72 to 168 hours 4224 to 72 hours ×: 24 hours or less (Example '1) A bright Ni-Zn alloy plated steel sheet obtained from a Ni-Zn alloy plating bath prepared to contain 12 ± 1% Ni with 0.5 f/l"k of polyamine sulfone added as a brightener was NaNO3/H3PO4=80 /7?/L (molar ratio 0.07) and NaNO3/H3PO410r
03 = 80/710.1 f/l p)l = Q, immersed in an aqueous solution of 8, subjected to blackening treatment, washed with water and dried,
evaluated. The appearance is a glossy black appearance (L value 12), W and O.
The gloss of the bath containing r03 was good. Adhesion workability was also good (rating: ◎), and in terms of corrosion resistance, it took 48 hours for white rust to develop.

(Example 2) A Ni-Zn alloy plated steel plate containing Ni 12±IX was subjected to the blackening treatment of Example 1, washed with water, and then coated with a protective film shown in Table 1.

The protective film was applied by roll coating an aqueous solution and baked with hot air to a board temperature of 120°C. Examples 1 and 2 of the present invention were coated with organic (1) and organic-inorganic polymer system (2). 3,
4 is an example of chromate treatment, 5 and 6 are inorganic rust prevention treatments, and 7 is a complete inorganic treatment. The quality was generally good.

Composition of protective film A: Aqueous dispersion of 10% acrylic ester emulsion and water-bathable melamine IX B: Polyethyleneimine emulsion IOX, colloidal silica 5, and silane coupling agent IX aqueous dispersion 0 ...ammonium polyacrylate IOX, lit ammonium chromate 2, aqueous solution of colloidal silica IX D...chromic acid/colloidal silica" = 2/4% aqueous solution E...Kt O/ 8 i 02 = 2 / 1
(Mole ratio) 10% aqueous solution F: Aqueous solution of ammonium zirconate IOX and polyacrylic acid IX G: 5X aqueous solution of magnesium salt of condensed phosphoric acid (Example 3) The alloy plated steel sheets shown in Table 2 were mixed in the molar ratio Sail 25 NaNO
3/HsPO410rO3=100/3 o/ o, o
2 f / L, pH = 0.8 aqueous solution for 5 seconds to perform blackening treatment, 5i (h10rO
Spray an aqueous solution of s = 415%, squeeze it with an xd3-roll squeezer, bake it on a board @ 60°C with hot air drying, and then apply a composite bath dry coating of polyethylene imine emulsion and colloidal silica to 1 μm, and the board temperature is 120°C. Baked at °C. The results are shown in Table 2.

Non-inventive example 8 in Table 2 shows the black effect of a ternary alloy film obtained by adding CO to I'H-Zn alloy plating. It is blackened. Appearance.

Corrosion resistance was good in all cases.

(Example 4) 12% Ni-Zn alloy was applied to a cold-rolled steel plate at 20 mm/ff1''
Immediately after plating, NaNOs/H3PO4
= 120 / 50t7t (molar ratio 0.35)
After blackening by spraying an aqueous solution of pi (== 0.7), washing with water, and performing electrolytic chromate treatment in a publicly available sulfuric acid bath, a commercially available silica-containing aqueous emulsion resin was applied to a film thickness of 1.
A black zinc alloy plated steel sheet was manufactured by coating with μ target and baking hardening. The obtained characteristic values are black ##) glossy (○)
Good results were obtained for workability (◎) and corrosion resistance (○).

(Effects of the invention) According to the present invention, a color-treated plated steel sheet with high V productivity can be obtained,
We can provide surface-treated steel sheets at low cost without reducing quality. Coloring was traditionally provided by paints, but
It is composed of a thin inorganic film and has excellent solvent resistance and
It has the advantage of being highly scratch resistant and not discolored. In particular, when a retentive 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.

The invention is a simple and efficient method that can uniformly blacken a wide coil using a simple immersion tank or spray tank that does not require expensive electrolysis equipment, and has the advantage of being applicable to existing processes. There is.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the 1i1 process of the present invention. ta> indicates alloy plating, (b) shows the reaction in a coloring treatment bath, and (C) 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 and one other person Figure 71'1 (Q) (, b)
(C) 7I'2 diagram → ljidesiL=

Claims (4)

[Claims] (1) The steel plate plated with an alloy of zinc and a metal that turns black is composed of nitrate and phosphoric acid, and the molar ratio of phosphoric acid/nitrate is 0.
．． 1. A method for producing a black zinc alloy plated steel sheet, which comprises spraying or immersion treatment in an acidic aqueous solution having a pH of 0.01 to 1.5 or less. (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) The method for manufacturing a black zinc alloy plated steel sheet according to claim 1, which uses an aqueous solution containing 0.01 to 1.0% of one or more of chromic acid, vanadic acid, molybdic acid, and peroxide. (4) Zinc and blackened metal alloy plated steel plate is composed of nitrate and phosphoric acid, and the molar ratio of phosphoric acid / nitrate is 0.
．． 1. A method for producing a black zinc alloy plated steel sheet, which comprises spraying or dipping the steel sheet in an acidic aqueous solution having a pH of 0.01 to 1.5 or less and coating it with a protective film.