JPH0422992B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing colored, particularly black steel sheets 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 requirements have shifted to lower costs and higher quality year by year, and steel manufacturers have developed new technologies and products to meet the demands of customers. In recent years, by introducing pre-coated steel sheets to products that were conventionally 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. There is a growing movement towards the use of pre-painted steel sheets to obtain 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. I'm getting used to it.

There is a strong need for a black color tone, and in addition to the above, the material is also required to be resistant to fingerprints, workability, chemical resistance, and corrosion resistance.

Conventional coloring methods generally apply to stainless steel, steel sheets, and copper, 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 the technique described in Japanese Patent Application Laid-Open No. 2002-12002, in which black chromate is treated in an aqueous chromate solution containing silver ions.
There is a method described in Publication No. 52-45544, 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. As a method of forming sulfides to obtain a black appearance, there is a method disclosed in JP-A-52-65139. Further, Japanese Patent Application Laid-open No. 58-151490 and Japanese Patent Application Laid-Open No. 58-151491 disclose a method of blackening by anodic electrolytic treatment. The former is produced in an alloy plating bath of Ni ²⁺ , Co ²⁺ , Mo ²⁺ and Zn ²⁺ , and the latter is produced by anodizing a steel plate plated with an alloy of Ni, Co, Mo and Zn in an ammonium sulfate aqueous solution. This is a method to form oxides of Co and Mo. Furthermore, Japanese Patent Application Laid-open No. 121275/1983 discloses a method of obtaining a black appearance by chemically dissolving a Ni-Zn alloy plated steel sheet in an aqueous solution of nitric acid or hypochlorite.

(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, anodizing greatly dissolves the plating on the substrate, which limits the plating on the substrate, and it is difficult to re-dissolve the plating once deposited.

In addition, in the conventional method, post-treatment such as chromate treatment is performed after coloring to ensure rust prevention and adhesion with the guard coat, which requires adding equipment to the existing surface treatment line.

The present invention solves these problems. It is possible to obtain a colored film at high speed and in a short time without depending on the base metal, and furthermore, post-treatment can be omitted. To provide a method by which a colored steel plate can be obtained.

(Means for Solving the Problems) The present invention provides water-soluble 4.
Contains 1 to 200 g of class amine polymer, 10 to 150 g of zinc ions in terms of sulfate, and 5 to 150 g of metal ions whose oxides are colored in terms of sulfate,
and a hexavalent chromium compound as a chemical conversion film forming agent,
A colored surface characterized by forming a colored film by electrolytically treating a steel plate or a galvanized steel plate as a cathode in an aqueous solution containing one or more of phosphates, sol, water-soluble polymers, and chelate compounds. Process for producing treated steel sheet and water-soluble quaternary amine polymer with average molecular weight from 1,000 to 1,000,000 1
~200g/ and zinc ion 10~150 in terms of sulfate
g/, containing 5 to 150 g/ of metal ions whose oxides are colored in terms of sulfate, and containing one or more of hexavalent chromium compounds, phosphates, sol, water-soluble polymers, and chelate compounds. This method of producing a colored surface-treated steel sheet is characterized in that a colored film is formed by electrolytically treating a steel sheet or a plated steel sheet in an aqueous solution using a cathode, and then a guard coat is applied to a thickness of 0.5 to 3 μm.

The invention is based on the cathodic deposition of zinc and coloring compounds and polymers and rust-inhibiting compounds onto metal surfaces.

The present inventors had previously 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 present invention has developed a method for obtaining high-quality colored surface-treated steel sheets using a simpler process.

The most important point of the present invention is that the alloy plating bath containing the quaternary amine polymer contains compounds that improve rust prevention and guard coating adhesion, such as hexavalent chromium compounds, phosphates, sols, and water-soluble polymers. ,
One or more chelate compounds (hereinafter referred to as
By using an aqueous solution containing a "chemical film forming agent", the conventional post-treatment after blackening and the guard coating depending on the purpose can be omitted.
The cathodically deposited coating obtained in the present invention is composed of zinc co-containing a cationic polymer, a coloring compound, and a conversion coating.

The aqueous solution contains zinc ions (Zn ²⁺ ), colored metal ions (Me ⁿ⁺ ), quaternary amine polymer ions (p ⁺ ), chemical conversion film forming agents (C), anions (A ^- ), and protons (H ⁺ ). exists. As shown in FIG. 1, zinc is deposited on the cathode surface due to the reduction of metal ions. At the same time, the quaternary amine polymer (symbol ~) is adsorbed to zinc and precipitated together with zinc.
Colored metal ions are reduced, but due to adsorption of polymer ions and preferential precipitation of zinc ions, they are not sufficiently reduced, and oxides with adsorbed polymers (symbol ○†a gun chopsticks)

Claims (1)

[Claims] 1. 1 to 200 g of a water-soluble quaternary amine polymer with an average molecular weight of 1,000 to 1 million, 10 to 150 g of zinc ions in terms of sulfate, and metal ions whose oxides are colored in terms of sulfate. 5-150g/contains, and
Hexavalent chromium compounds, phosphates, sols, water-soluble polymers, chelate compounds as chemical conversion film forming agents
1. A method for producing a colored surface-treated steel sheet, which comprises forming a colored film by electrolytically treating a steel sheet or a plated steel sheet in an aqueous solution containing one or more seeds as a cathode. 2. The method for producing a colored surface-treated steel sheet according to claim 1, wherein the pH of the aqueous solution is adjusted to 1.5 to 3.0. 3 Contains 1 to 200 g of a water-soluble quaternary amine polymer with an average molecular weight of 1,000 to 1 million, 10 to 150 g of zinc ions in terms of sulfate, and 5 to 150 g of metal ions whose oxides are colored in terms of sulfate. ,and,
After forming a colored film by electrolytically treating a steel plate or plated steel plate as a cathode in an aqueous solution containing one or more of hexavalent chromium compounds, phosphates, sols, water-soluble polymers, and chelate compounds. , a method for manufacturing a colored surface-treated steel sheet, characterized by applying a guard coat of 0.5 to 3 μm.