Single-Bath Electrochemical Passivation Solution for Metal Substrates
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Solution Overview
Problem
Current passivation treatments for metal substrates, such as chromate conversion coating, face challenges due to toxicity and the occurrence of undesired precipitations when using alternative materials like metal cations and metal-oxide anions in electrochemical processes, which limits their effectiveness in forming protective layers without chemical reactions.
Innovation Solution
A single-bath electrochemical passivation solution composition comprising a metal cation, metal-oxide anion, organic ligand, and polymer is used, where the organic ligand forms a complex with the metal cation to prevent precipitation, and a non-metallic oxide anion is included to form a composite oxide film, allowing for controlled deposition without spontaneous reactions, using a pH range of 5 to 12 and specific electric current parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If alternative materials (metal cation, metal oxide, non-metallic ion) are used instead of chromate for passivation treatment, then toxicity is reduced, but undesired precipitations occur due to chemical reactions between ionic chemical species in electrolyte or aqueous solution before electrochemical treatment process
Solution Approach 1:
An organic ligand is introduced as an intermediary substance that forms stable complexes with metal cations (such as Ce3+). This complexation prevents direct precipitation reactions between metal cations and metal-oxide anions in the aqueous solution, while still allowing controlled electrochemical deposition during the passivation process. The organic ligand acts as a mediator that enables the use of alternative non-toxic materials without suffering from precipitation issues.
2Reliability
If chromate conversion coating is used for passivation treatment, then corrosion resistance is improved, but toxicity and carcinogenicity increase
Solution Approach 1:
The invention changes the chemical composition parameters of the passivation solution by replacing toxic chromate ions with alternative non-toxic materials such as metal cations (Ce3+, Pr3+), metal oxides, and non-metallic ions. By carefully controlling the pH range (5-12) and using organic ligands to complex metal cations, the solution achieves effective passivation without the harmful effects of chromate, thus changing the material parameters while maintaining protective function.
3Reliability
If metal cation and metal-oxide anion are used in electrochemical process, then corrosion resistance is enhanced, but chemical reactions occur in electrolyte before treatment process, producing undesired precipitations
Solution Approach 1:
The organic ligand performs a preliminary action by forming stable complexes with metal cations before the electrochemical treatment process begins. This pre-complexation prevents spontaneous precipitation reactions that would otherwise occur when metal cations and metal-oxide anions come into contact in the electrolyte solution. The preliminary complexation ensures that metal cations remain in solution until controlled deposition is initiated by the electrochemical process, thereby maintaining manufacturing precision.
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
This approach enables the formation of stable composite oxide films on metal substrates, enhancing corrosion resistance and adhesion without the formation of undesired precipitates, thus providing a high-performance passivation treatment that replaces toxic chromate-based methods.
Implementation Method 1
the organic ligand forms a complex with the metal cation
Implementation Method 2
applying an electric current to the substrate to perform electrodeposition
Implementation Method 3
applying a secondary electric current to the substrate in the solution composition to perform a second electrodeposition
Data Source
Figure 1~2
Figure 3~4
AI summary
Disclosed is a solution composition which may be used for a single-bath electrochemical passivation and a method using the same. The solution composition includes a metal cation, a metal-oxide anion; and an organic ligand, and optionally includes a non-metallic oxide anion or a polymer. The solution composition may prevent undesired precipitation of metal oxides before performing passivation. In addition, the method of passivation using the solution composition in a single-bath use is also provided.