Cobalt-Free Chemical Conversion Liquid for Corrosion Resistance
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Solution Overview
Problem
The challenge is to develop a cobalt-free trivalent chromium-containing chemical conversion treatment liquid that forms a corrosion-resistant film without using water-soluble cobalt-containing substances, while also considering environmental preservation, as cobalt is difficult to obtain at low cost and its compounds are substances of very high concern, and excessive dissolution of metal-based components from chemical conversion films can harm the environment.
Innovation Solution
A chemical conversion treatment liquid comprising water-soluble trivalent chromium, titanium, and lactic acid, with specific molar concentration ratios and optionally including glycolic acid or other organic acids, along with other components like aluminum, nickel, or silica, to form a stable and corrosion-resistant film on metal surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water-soluble cobalt-containing substances are used to improve corrosion resistance, then the corrosion resistance of the chemical conversion film is improved, but the environmental safety deteriorates due to cobalt being a substance of very high concern and the cost increases due to cobalt being a rare metal
Solution Approach 1:
The invention extracts and removes the harmful cobalt component from the chemical conversion treatment liquid while maintaining the corrosion resistance function through alternative components. The treatment liquid is designed to be substantially free from water-soluble cobalt-containing substances, eliminating the environmental hazard while preserving the protective function of the chemical conversion film.
Solution Approach 2:
The invention changes the compositional parameters of the treatment liquid by specifying precise molar concentration ratios of titanium-containing substance to chromium-containing substance (0.1 to 5.0) and organic acid to metal components (0.01 to 1.0). These parameter changes enable the formation of a corrosion-resistant film without requiring cobalt, thus resolving the contradiction between corrosion resistance and environmental safety.
2Reliability
If water-soluble cobalt-containing substances are used to improve corrosion resistance, then the corrosion resistance of the chemical conversion film is improved, but the cost increases due to cobalt being difficult to obtain at low cost
Solution Approach 1:
The invention extracts and removes the expensive cobalt component from the treatment liquid formulation. By eliminating cobalt and using alternative substances such as titanium-containing substances and organic acids, the invention reduces material costs while maintaining the corrosion resistance performance through optimized compositional ratios.
Solution Approach 2:
The invention replaces expensive rare metal cobalt with more readily available and cost-effective substances. The treatment liquid uses common chemicals like titanium salts, chromium salts, and organic acids that can be obtained at lower costs, making the manufacturing process more economically viable while achieving the same protective function.
3Reliability
If excessive dissolution of metal-based components occurs from the chemical conversion film, then the corrosion resistance may be enhanced, but the environmental safety deteriorates due to harmful metal dissolution
Solution Approach 1:
The invention changes the chemical composition parameters of the treatment liquid to achieve a balanced film structure. By controlling the molar concentration ratios of titanium to chromium (0.1 to 5.0) and organic acid to metal components (0.01 to 1.0), the film achieves adequate corrosion resistance while limiting excessive metal dissolution through the stabilizing effect of organic acids that form protective complexes with metal ions.
Solution Approach 2:
The invention introduces organic acids as intermediary substances that mediate between the metal components and the environment. These organic acids form coordination complexes with metal ions, reducing their solubility and preventing excessive dissolution into the environment while maintaining the protective function of the chemical conversion film.
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 provides a cobalt-free chemical conversion film with excellent corrosion resistance and environmental preservation, ensuring stability and reducing the risk of metal-based component dissolution, thus addressing the limitations of existing technologies that rely on cobalt and hexavalent chromium.
Implementation Method 1
chemical conversion treatment liquid that contains a water-soluble trivalent chromium-containing substance, a water-soluble titanium-containing substance, and a water-soluble lactic acid-containing substance to form a chemical conversion film
Data Source
AI summary
The chemical conversion treatment liquid according to the present invention, which is cobalt-free and is capable of forming a chemical conversion film having excellent corrosion resistance, contains a water-soluble trivalent chromium-containing substance, a water-soluble titanium-containing substance, and a water-soluble lactic acid-containing substance as essential components and may optionally contain a component at least a part of which is any of a water-soluble glycolic acid-containing substance and a water-soluble ineffective organic acid-containing substance. The water-soluble ineffective organic acid-containing substance is a water-soluble organic acid-containing substance based on an ineffective organic acid that is an organic acid other than lactic acid and other than glycolic acid. When the chemical conversion treatment liquid does not contain the water-soluble glycolic acid-containing substance and does not contain the water-soluble ineffective organic acid-containing substance, a titanium-equivalent molar concentration CTi of the water-soluble titanium-containing substance, a chromium-equivalent molar concentration CCr of the water-soluble trivalent chromium-containing substance, and a lactic acid-equivalent molar concentration CLc of the water-soluble lactic acid-containing substance satisfy the following Expressions (1) to (3): CTi/CCr≥0.5 CLc/CTi+CCr≥0.40 and CLc/CTi≤2.6