Chemically Colored Stainless Steel Gloss Control
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Solution Overview
Problem
Stainless steel products often exhibit color unevenness and poor viewing-angle color tone discrimination due to inadequate control over oxide film thickness during chemical coloring processes, limiting their ability to achieve warm color tones and sophisticated industrial colors.
Innovation Solution
A method involving a combination of sandblasting and electrolytic polishing treatments followed by a chemical coloration process using a mixed solution of chromic acid and sulfuric acid, with a curing treatment in phosphoric acid, to achieve a 60-degree specular gloss of 5 to 50 and a colored film thickness of 90 nm to 220 nm, ensuring uniform coloration and reduced color unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxidation coloring is performed on stainless steel to generate a colored film, then coloration is achieved, but color unevenness is easily generated due to inability to uniformly control oxide film thickness
Solution Approach 1:
The patent applies preliminary sandblasting treatment to create uniform surface roughness before chemical coloration. This preliminary action ensures that the subsequent oxide film forms uniformly across the surface, preventing color unevenness while maintaining the desired coloration effect.
Solution Approach 2:
The patent changes the surface state parameter by controlling the roughness ratio (Rs/Rz) to be 0.85 or more through sandblasting. This parameter change creates optimal conditions for uniform oxide film formation during chemical coloration, resolving the color uniformity issue.
2Illumination intensity
If stainless steel surface is made highly reflective, then metallic luster is enhanced, but viewing-angle color tone discrimination deteriorates due to strong silver-white metallic luster
Solution Approach 1:
The patent changes the surface optical parameter by controlling the specular gloss to be 5 to 50 at 60 degrees. This parameter change reduces the strong silver-white metallic luster while maintaining sufficient brightness, thereby improving viewing-angle color tone discrimination.
Solution Approach 2:
The patent creates local surface quality variations through sandblasting that produce controlled roughness. This local quality change diffuses reflected light, reducing the intensity of metallic luster in specific directions while improving color tone visibility from different angles.
3Difficulty of detecting and measuring
If sandblasting treatment is performed to create uneven surface, then gloss level is reduced and viewing-angle color tone discrimination is improved, but color unevenness may occur without proper electrolytic polishing
Solution Approach 1:
The patent merges sandblasting treatment with electrolytic polishing treatment in a combined process. The sandblasting creates initial surface roughness for reduced gloss, while the subsequent electrolytic polishing refines the surface to ensure uniform oxide film formation, eliminating color unevenness while maintaining improved viewing-angle color tone discrimination.
Solution Approach 2:
The patent applies continuous sequential treatments: sandblasting followed by electrolytic polishing, then chemical coloration. This continuous process ensures that each treatment builds upon the previous one, maintaining surface uniformity while achieving the desired gloss reduction and color uniformity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in stainless steel products with inconspicuous color unevenness and excellent viewing-angle color tone discrimination, allowing for the development of sophisticated industrial color tones with reduced color variation across different angles.
Implementation Method 1
spraying a mixture of a grinding material and compressed air on a surface of stainless steel to form an uneven surface on the surface of stainless steel
Implementation Method 2
an electrolytic polishing treatment step of electropolishing the sandblasted stainless steel
Implementation Method 3
a coloration treatment step of dipping the electropolished stainless steel in a coloring treatment solution consisting of a mixed solution of a chromic acid and a sulfuric acid to generate a colored film
Data Source
AI summary
[Problem] There is provided a colored stainless-steel product having excellent viewing-angle color tone discrimination and excellent corrosion resistance, in which a chemical coloration technique having sophisticated industrial color tone is used.[Solution] The product is a chemically-colored stainless-steel product having an uneven surface formed by a grinding treatment, wherein the 60-degree specular gloss [Gs (60 degrees)] of the uneven surface is 5 to 50. The grinding treatment is performed by a single sandblasting treatment or a combination of the sandblasting treatment and an electrolytic polishing treatment. The sandblasting treatment is performed with a projection material configured from inorganic particles having a Mohs' hardness of at least six. A manufacturing method includes a sandblasting treatment step, an electrolytic polishing treatment step, a coloration treatment step for dipping stainless steel in a coloration treatment solution including a mixed solution of a chromic acid and a sulfuric acid to generate a colored film thereon, and a curing treatment step for dipping the coloration-treated stainless steel in a curing treatment solution including a mixed solution of a chromic acid and a phosphoric acid to cure the colored film.