Black Trivalent Chromium Conversion Coating for Stable Corrosion Resistance
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Solution Overview
Problem
Existing chemical conversion treatments using trivalent chromium compositions face challenges in maintaining both black appearance and high corrosion resistance as the cumulative treated area increases, particularly under fixed-quantity replenishment management.
Innovation Solution
A composition comprising trivalent chromium, an organic sulfur compound, an organic phosphonic acid compound, a vanadium-containing substance, and a hydroxycarboxylic acid-containing substance, with specific molar concentration ratios, is used to form a chemical conversion coating film that maintains black appearance and high corrosion resistance even with increased cumulative treated area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a composition containing trivalent chromium ions is used to form black coating films, then the composition is hexavalent chromium-free and environmentally friendly, but the stability of the composition deteriorates and the black appearance of the coating film deteriorates as the cumulative treated area increases
Solution Approach 1:
The invention changes the chemical composition parameters by introducing a vanadium-containing substance in a specific concentration range (0.01-1 mol/L) and controlling the molar ratio between vanadium and chromium (1:10 to 10:1). This parameter adjustment stabilizes the composition and maintains coating quality over extended cumulative treated areas while keeping the composition hexavalent chromium-free.
Solution Approach 2:
The invention creates a composite chemical system combining trivalent chromium ions with vanadium-containing substances to form a synergistic composition. This composite approach leverages the corrosion resistance of chromium while adding vanadium's stabilizing effects, resulting in a composition that maintains both stability and black appearance even after treating large cumulative areas.
2Productivity
If the cumulative treated area increases, then production volume increases, but the black appearance of the coating film deteriorates and turns gray
Solution Approach 1:
The vanadium-containing substance acts as a self-regulating component that continuously stabilizes the composition during extended use. As the cumulative treated area increases, the vanadium compounds maintain the chemical balance and prevent the degradation that would otherwise cause the coating to turn gray, enabling continuous black appearance maintenance.
Solution Approach 2:
The invention preemptively adds vanadium-containing substances to the composition to cushion against future degradation. This prior cushioning ensures that even after treating large cumulative areas, the composition remains stable enough to produce black coating films, preventing the gray coloration that would occur without this preventive measure.
3Productivity
If the cumulative treated area increases, then production volume increases, but corrosion resistance of the coating film deteriorates
Solution Approach 1:
The invention adjusts the compositional parameters by incorporating vanadium-containing substances at controlled concentrations (0.01-1 mol/L) and maintaining specific molar ratios. This parameter optimization ensures that corrosion resistance is maintained at high levels even after the composition has been used to treat large cumulative areas, enabling continuous production without reliability degradation.
Solution Approach 2:
The composite system of chromium and vanadium compounds provides synergistic protection. The vanadium component enhances and stabilizes the corrosion resistance mechanism, allowing the coating to maintain high reliability even as the cumulative treated area increases and the composition undergoes extended use.
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 composition stabilizes the quality of the chemical conversion coating film, ensuring consistent black appearance and corrosion resistance over extended cumulative treated areas with simplified fixed-quantity replenishment management, thus supporting mass production stability.
Implementation Method 1
a composition for chemical conversion treatment comprising a trivalent chromium-containing substance, an organic sulfur compound, an organic phosphonic acid compound, a vanadium-containing substance, and a hydroxycarboxylic acid-containing substance
Implementation Method 2
an organic sulfur compound and an organic phosphonic acid compound composed of one or more compounds selected from the group consisting of organic phosphonic acids and their ions and salts are added
Data Source
AI summary
Composition for chemical conversion treatment according to an aspect of the present invention contains a trivalent chromium-containing substance, an organic sulfur compound, an organic phosphonic acid compound, a vanadium-containing substance, and a hydroxycarboxylic acid-containing substance, and can therefore form a chemical conversion coating film that combines a black appearance and high corrosion resistance even when the cumulative treated area increases through fixed-quantity replenishment management. The composition for chemical conversion treatment may have a ratio of the vanadium-equivalent molar concentration of the vanadium-containing substance to the hydroxycarboxylic acid-equivalent molar concentration of the hydroxycarboxylic acid-containing substance of 1:1 to 1:10.