JPH03162598A - Production of lustrous black steel material - Google Patents

Abstract

PURPOSE:To continuously produce a lustrous black plated steel material at a high speed by plating a steel material with a bath prepd. by adding tungstic acid to a Zn alloy plating bath under the conditions of a specified current density and a specified quantity of electricity. CONSTITUTION:A steel material is plated with a bath prepd. by adding about 0.5-100g/l tungstic acid to a Zn alloy plating bath under the conditions of 5-500A/dm<2>, preferably 10-100A/dm<2> current density and >=50C/cm<2>, preferably 100-800C/dm<2> quantity of electricity. The plated steel material is post-treated by chromating to form a chromate film by 3-200mg/m<2> (expressed in terms of Cr) and a protective film as the outermost layer is formed by applying a water soluble resin or silica sol by 0.3-3g/m<2> on dry basis. A lustrous black steel material having superior blackness and satisfactory adhesion is produced at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for continuously producing glossy black-plated steel at high speed. (Prior art) Light'/R black steel materials (hereinafter simply referred to as "black tlAjH"), such as black steel sheets, which are widely used in home appliances, copying machines, information communication equipment, automobile interiors, interior building materials, etc., are manufactured by manufacturers. Steel plates are processed and manufactured using methods such as painting, electroplating, and chromate treatment.

In recent years, steel manufacturers have begun to produce black-plated conditioned plates using post-treatment electrolytic methods from zinc-based alloy plated materials in order to shorten processes and reduce costs. Conventional blackening treatment methods include (;) black painting method, (ii) black chromate method,
(iii) Chemical treatment method ((a) Unexamined Japanese Patent Publication No. 1989-
55546, Cb) JP-A-52-76237, (C) JP-A-52-76238, (d)
JP-A-60121275, (e) JP-A-60-1
81277), (iv) heat treatment method (Japanese Unexamined Patent Application Publication No. 1983)
-91993, JP-A-56-293)
, (v) Anodic electrolytic treatment method (Japanese Patent Application Laid-Open No. 58-15149
No. 0, Japanese Unexamined Patent Publication No. 151491/1982), (v
i) There is a cathodic electrolytic treatment method (Japanese Unexamined Patent Publication No. 190588/1988). (Problems to be Solved by the Invention) However, (i) the black painting method requires painting equipment, which requires expensive equipment investment and increases manufacturing costs. (ii) The black chromate method requires a long reaction time and cannot be continuously processed in an electroplating line. The drug is also expensive because it uses salt.

(iii) Chemical treatment methods (a) to (C) are a type of displacement plating that uses copper ions, and the temperature of the treatment solution,
Because the concentration affects the reaction rate and Zn and the like dissolve in the treatment liquid, uniform black treatment cannot be achieved in high-speed line production. Furthermore, sufficient film strength cannot be obtained from the blackened layer. (d) and (e) are oxidation reactions carried out in an aqueous nitric acid solution, and are basically the same as (a) to (C); Zn, Ni, etc. are dissolved in the treatment solution, and the short-term The processing solution deteriorates during this time. Furthermore, the blackening layer thus formed also has a low degree of blackness, and only a bluish tone can be obtained.

(iv) Heat treatment requires expensive equipment, and it is difficult to control uniform heating, making it difficult to control coloration. (v) The anodic electrolytic treatment method is described in Japanese Unexamined Patent Publications No. 58-151491 and No. 58-151490 as having the advantage that blackening can be controlled by the amount of electricity. However, the plating metal dissolves into the electrolytic solution, causing deterioration of the solution, and the plating metal must be melted again, which is economically disadvantageous.

(vt) The cathodic electrolytic treatment method is an excellent treatment method in that it eliminates the dissolution of the plating layer, which is the drawback of (v), but the blackness cannot be obtained unless the blackening layer is relatively thick. The disadvantage is that the thicker the layer, the worse the strength and adhesion.

As described above, in the conventional technology described above, the anodic electrolysis method that can achieve blackening at high speed causes Ni and Zn ions to accumulate in the electrolyte, making it necessary to replace the electrolyte, resulting in high costs. The cathodic electrolytic method other than 1 requires thickening of the film, and has the disadvantage that the thicker the film, the weaker the adhesion.

Thus, an object of the present invention is to solve each of the drawbacks of the conventional methods described above and to provide a method for manufacturing a steel material having an excellent black film.

(Means for Solving the Problems) In order to achieve the above object, the present inventors have studied these problems and have focused on plating using a cathode method that does not cause liquid contamination in the electrolytic method. In order to overcome these shortcomings, various studies were conducted, and by electrolyzing in a zinc alloy plating bath with tungstic acid added'! 13 It was discovered that it was possible to obtain a glossy black steel material with excellent adhesion, and the present invention was completed.

Here, the present invention provides a method for producing a bright black steel material, which comprises plating a steel material in a Zn-based alloy plating bath with tungstic acid added at a current density of 5 to 500 A/dm2 and an electrolytic i of 150 coulombs/dm2 or more. be.

As described above, according to the method of the present invention, since the steel material can be directly blackened (plated), it has excellent blackness even if it is thin, and has good adhesion, and unlike cathode blackened materials, the base material is exposed due to processing scratches etc. There are no drawbacks such as doing so.

Moreover, with the method of directly obtaining a black film without dissolving the base material using cathodic electrolysis, which does not contaminate the electrolyte, the amount of electricity required to obtain a black film can be achieved with a minimum of 50 coulombs/dta, which is a high-speed process in seconds. It is possible to obtain a stable and glossy black film.

Furthermore, two possible methods for continuously blackening steel materials include a method of anodizing zinc-based alloy plated materials to blacken them through a reaction of melting and oxidation, and using additives directly in the zinc-based alloy plating bath. However, the method of the present invention is a post-sweat method, and a glossy black film is created by depositing zinc-based alloy + tungsten oxide by cathodic lightning decomposition in an electrolytic bath containing tungstic acid. can be obtained rapidly and continuously. The materials to be treated by the method of the present invention are:
Any material that can be plated can be used, such as plates, rods, pipes, stainless steel, etc. In order to carry out continuous processing, it is preferable to treat steel plates.

(effect) Next, the structure of the present invention will be explained.

The zinc-based alloy plating bath used in the present invention refers to a plating bath containing zinc as a main component and nickel, iron, and cohardt as other components.

The tungstic acid added to the zinc-based alloy plating bath may be of any type as long as it dissolves in the acidic plating bath, but sodium tungstate and ammonium tungstate are easily soluble. There is no particular restriction on the amount added to the plating bath, but preferably 0.5 to 100 g#! It is. It is possible to carry out the electric 2it density in the range of 5 to 500 A/dm2, but if it is less than 5 A/dm2, it will not turn black and 1
At 00 A/dm2 gJ, the precipitates become warped and form a film with poor adhesion. Preferably lO~100 A/d
It is m2.

If the amount of electricity is 50 coulombs/dm2 or more, a stable black film will be obtained, but if it is less than 50 coulombs/dm2, the base surface will not be completely covered, so the L value (lightness), which is an index of blackness, will be high. ．． The upper limit of the amount of electricity can be set to any value, but if it increases, the electrolysis time becomes longer, which is unproductive, and the film becomes thicker, causing problems such as poor adhesion. Practically speaking, the amount of electricity is preferably 100 to 800 coulombs/dm2. Chromate treatment is performed as a post-treatment to improve the corrosion resistance of the black film. The type of chromate is not particularly limited, and may be, for example, a conventional reactive chromate or a coating-type chromate. The amount of adhesion is cr.
tA calculation is 3 to 200 mg/a", 3 mg7m"
If it is less than 200s+g/+*, the corrosion resistance effect will be small.
"Ultra-thickness causes problems in paint adhesion. The protective coating after chromate treatment is applied to improve corrosion resistance, abrasion resistance, and fingerprint resistance, and there are no particular restrictions on the type of resin, but there are online From the viewpoint of implementation, it is preferable to use water-soluble resins such as acrylic and epoxy.In addition to water-soluble resins, the same effect can be seen by applying silicic acid sol.The amount of adhesion is 0.3 to 3 g in terms of dry film weight. /m2
If it is less than 0.3 g/s", the corrosion resistance, abrasion resistance, and anti-fingerprint performance will not be sufficient, and if it exceeds 3 g/s", problems such as separation of the film during processing will occur. (Example) The present invention will be specifically explained using an example. The plating bath composition and plating conditions shown in Table 1 were used to conduct the plating, and the type of chromate film, amount of coating, and protective film were also listed.
Comparative examples are also shown in Table 1. Each alloy component added to the plating bath was added as a silicate, and the other composition was 80 g/l of ammonium sulfate. Bath pl1 is 2
．． 0, the temperature was 50°C. The obtained plating material was tested for blackness, corrosion resistance (SST), and film adhesion, and the results are summarized in Table 2. In the table, Erichsen refers to the plating film peeling test method in which a plated plate is stretched out using a testing machine specified in JISZ 2247. Table 2 (continued on next page) (Table 2 continued) (Effects of the invention) Since the present invention is designed as explained above, it is possible to easily form a film having excellent blackness and corrosion resistance and paint adhesion. This makes it possible to conduct a variety of disciplines, and the industrial benefits are extremely large.

Claims (2)

[Claims] (1) A method for producing glossy black steel material, which comprises plating steel material in a Zn-based alloy plating bath with tungstic acid added at a current density of 5 to 500 A/dm^2 and an electrolytic amount of 50 coulombs/dm^2 or more. . 2. The method for producing a glossy black steel material according to claim 1, further comprising: (2) applying chromate treatment containing chromic anhydride as a main component to the surface in an amount of 3 to 200 mg/m^2 in terms of Cr. 3. The method for producing a glossy black steel material according to claim 2, further comprising: (3) applying a water-soluble resin or silicic acid sol as a protective film on the uppermost surface at a dry weight of 0.3 to 3 g/m^2.