Surface-Treated Steel Sheets for Corrosion Resistance and Thick-Resin Adhesion
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Solution Overview
Problem
Existing methods for producing chromate-free surface-treated steel sheets fail to ensure adequate corrosion resistance and adhesion when an organic resin layer of 60 μm or more is formed, especially under severe conditions, and do not address the storage stability of the surface-treatment solution.
Innovation Solution
A surface-treatment solution comprising specific ratios of a resin compound, cationic urethane resin emulsion, silane coupling agent, organic titanium chelate compound, tetravalent vanadium compound, molybdate compound, and fluorine compound, applied at a pH of 4 to 5, forming a surface-treatment layer with a coating weight of 0.005 g/m² to 0.18 g/m², enhances corrosion resistance and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional surface-treatment solution is used to form a surface-treatment layer, then blackening resistance is improved, but corrosion resistance deteriorates when an organic resin layer of 60 μm or more in thickness is formed
Solution Approach 1:
The invention changes the chemical composition parameters of the surface-treatment solution by incorporating specific compounds (silane coupling agent, fluorine compound, titanium compound, vanadium compound, molybdate compound) in optimized ratios. This parameter optimization ensures that the surface-treatment layer maintains both blackening resistance and corrosion resistance even when a thick organic resin layer (60 μm or more) is formed, resolving the contradiction between these two properties.
2Object-affected harmful factors
If a conventional surface-treatment solution is used, then blackening resistance is improved, but adhesion between layers deteriorates under severe conditions
Solution Approach 1:
The invention creates a composite surface-treatment layer by combining multiple functional compounds: silane coupling agent for adhesion promotion, fluorine compound for corrosion resistance, titanium compound for surface stabilization, vanadium compound for blackening resistance, and molybdate compound for additional protection. This composite structure ensures both excellent blackening resistance and strong adhesion between the surface-treatment layer, organic resin layer, and coated layer even under severe conditions.
3Ease of manufacture
If a conventional surface-treatment solution is used, then processing is simplified, but storage stability of the surface-treatment solution deteriorates
Solution Approach 1:
The invention optimizes the pH parameter of the surface-treatment solution to a specific range (4.0-5.5) and carefully controls the concentrations of all components including the silane coupling agent, fluorine compound, titanium compound, vanadium compound, and molybdate compound. This parameter optimization ensures the solution remains chemically stable during storage while maintaining ease of application and processing, resolving the contradiction between storage stability and processing simplicity.
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 produces a surface-treated steel sheet with excellent blackening resistance, corrosion resistance, and adhesion between layers, even under severe conditions, while maintaining storage stability of the surface-treatment solution.
Implementation Method 1
applying, to surfaces of a zinc or zinc alloy coated or plated steel sheet, a surface-treatment solution containing specific compounds to form a surface-treatment layer
Data Source
AI summary
Disclosed is a method of producing a surface-treated steel sheet for organic resin coating comprising: applying, to a surface of a zinc or zinc alloy coated or plated steel sheet, a surface-treatment solution containing a resin compound having a specific bisphenol skeleton, a cationic urethane resin emulsion, a silane coupling agent having a specific reactive functional group, an organic titanium chelate compound, a tetravalent vanadium compound, a molybdate compound, a fluorine compound, and water in a specific ratio and with a pH of 4 to 5 to form a surface-treatment layer such that a coating weight of the surface-treatment layer per surface after drying of the surface-treatment solution is 0.005 g/m2 to 1.8 g/m2.