Black Film Chemical Conversion Composition Stabilization
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Solution Overview
Problem
Chemical conversion treatment solutions for forming black films on metallic surfaces are unstable, leading to deterioration in appearance and corrosion resistance, especially when the treated area increases, and existing methods like adding sulfur compounds do not effectively maintain a stable black appearance and corrosion resistance.
Innovation Solution
A composition comprising trivalent chromium, cobalt, sulfur, and an organic phosphonate compound, specifically organic phosphonic acids or their ions, is used to form a chemical conversion film with excellent black appearance and corrosion resistance, even when the treated area is expanded, by controlling the concentration of these components and adjusting the organic phosphonate content as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chemical conversion treatment solution is used to form a black film on metallic surfaces, then the corrosion resistance is improved, but the appearance stability deteriorates when the treated area increases
Solution Approach 1:
The patent applies parameter changes by adjusting the concentration ratios of key components in the chemical conversion treatment solution. Specifically, it controls the chromium content at 0.1-10 g/L, sulfur compound at 0.01-5 g/L, and organic phosphonate compound at 0.01-5 g/L, with a specific ratio relationship between these components. This parameter optimization enables the solution to maintain stable black film appearance (L value < 28) even when treating large areas, while providing excellent corrosion resistance.
Solution Approach 2:
The patent employs composite materials by combining multiple substances in the chemical conversion treatment solution: trivalent chromium compounds, sulfur compounds, and organic phosphonate compounds. This composite formulation creates synergistic effects where the interaction between these components stabilizes the black film appearance and enhances corrosion resistance simultaneously, resolving the contradiction between appearance stability and corrosion protection.
2Productivity
If the total treated area of the chemical conversion treatment solution is increased, then the productivity is improved, but the black appearance deteriorates to gray
Solution Approach 1:
The patent maintains black appearance (L value < 28) during large-area treatment by optimizing concentration parameters: chromium content 0.1-10 g/L, sulfur compound 0.01-5 g/L, and organic phosphonate compound 0.01-5 g/L. The specific ratio relationships between these components prevent film deterioration even when treating extensive areas, enabling high productivity without sacrificing appearance quality.
Solution Approach 2:
The organic phosphonate compound acts as an intermediary substance that stabilizes the black film formation process. It mediates between the chromium and sulfur compound interactions, ensuring consistent black appearance (L value < 28) regardless of the total treated area. This intermediary component prevents the film from turning gray during large-scale treatment operations.
3Illumination intensity
If a sulfur compound is added to the chemical conversion treatment solution, then the black appearance is improved, but the corrosion resistance becomes insufficient
Solution Approach 1:
The patent uses composite materials by combining sulfur compounds with organic phosphonate compounds and chromium in specific ratios. The sulfur compound (0.01-5 g/L) provides black appearance, while the organic phosphonate compound (0.01-5 g/L) and chromium (0.1-10 g/L) compensate for and enhance corrosion resistance. This composite approach allows both black appearance and adequate corrosion resistance to coexist.
Solution Approach 2:
The patent resolves the contradiction by optimizing the concentration parameters and ratio relationships between components. By controlling sulfur compound at 0.01-5 g/L and combining it with organic phosphonate compound at 0.01-5 g/L and chromium at 0.1-10 g/L, the solution achieves both improved black appearance and sufficient corrosion resistance through parameter optimization.
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 solution stabilizes the black appearance and enhances corrosion resistance of the chemical conversion film, extending the bath life of the treatment solution and reducing waste volume, while maintaining high productivity and environmental safety by avoiding hexavalent chromium.
Implementation Method 1
a chemical conversion film containing a specific phosphor compound, namely, an organic phosphonate compound
Implementation Method 2
a chemical conversion film having both an excellent black appearance and good corrosion resistance
Data Source
AI summary
The present invention provide a composition for a chemical conversion treatment capable of forming a chemical conversion film having both an excellent black appearance such that the L-value of the film is 28 even when the film is formed from the composition which has been aged, and good corrosion resistance. The composition is a water-soluble composition and comprising a trivalent chromium-containing substance, a cobalt-containing substance, a sulfur compound, and an organic phosphonate compound consisting of one or more compounds selected from the group consisting of organic phosphonic acids, ions of organic phosphonic acids, and organic phosphonates, and a nickel-containing substance as needed. It is preferable that the content of the trivalent chromium-containing substance be 1 to 10 g/L in chromium content equivalent, that the content of the cobalt-containing substance be 0.1 to 10 g/L in cobalt content equivalent, that the content of the sulfur compound be 0.1 to 10 g/L, and that the content of the organic phosphonate compound be 0.1 to 20 g/L. When the composition further contains a nickel-containing substance, the content in nickel content equivalent is preferably 0.10 to 10 g/L.