Sn-plated steel sheet oxide layer yellow stain resistance
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Solution Overview
Problem
Sn-plated steel sheets without chromate treatment suffer from inadequate yellow stain resistance, lacquer adhesion, and sulphide stain resistance due to the growth of oxygen-deficient tin oxide, which leads to appearance yellowing and adhesion deterioration over time.
Innovation Solution
An Sn-plated steel sheet with a coating layer containing zirconium oxide and tin oxide, where the zirconium oxide content is between 0.2 mg/m2 and 50 mg/m2, and the peak position of binding energy of Sn3d5/2 in the tin oxide is 1.6 eV or higher than that of metal Sn, along with a phosphorus content in a specific mass ratio, to suppress the growth of oxygen-deficient tin oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromate treatment is applied to Sn-plated steel sheet, then yellow stain resistance, lacquer adhesion, and sulphide stain resistance are improved, but environmental safety deteriorates due to hexavalent chromium content
Solution Approach 1:
The patent removes the harmful chromate treatment step entirely from the manufacturing process. Instead of applying chromate solution, the invention uses a simple heat treatment process that forms a protective oxide layer on the Sn plating layer, thereby extracting the harmful substance (hexavalent chromium) from the system while maintaining the protective functions.
Solution Approach 2:
The patent converts the naturally occurring oxidation of Sn (which would normally cause yellowing) into a beneficial process. By controlling heat treatment conditions, the oxidation forms a stable, protective oxide layer that prevents further degradation and provides the desired yellow stain resistance, lacquer adhesion, and sulphide stain resistance without environmental harm.
2Strength
If chromate treatment is applied to Sn-plated steel sheet, then lacquer adhesion is improved through prevention of cohesive failure, but environmental safety deteriorates
Solution Approach 1:
The patent eliminates the chromate treatment step that provides lacquer adhesion promotion, and replaces it with a heat treatment process that forms a stable oxide layer. This extraction removes hexavalent chromium from the system while maintaining the adhesion function through a different mechanism.
Solution Approach 2:
The patent changes the chemical and physical parameters of the surface layer by controlling heat treatment conditions (temperature, time, atmosphere). This transforms the surface composition to form a stable oxide layer with appropriate surface properties for lacquer adhesion, replacing the chromate-based adhesion mechanism with an oxide-based mechanism.
3Object-affected harmful factors
If no chromate treatment is applied to Sn-plated steel sheet, then environmental safety is improved, but yellow stain resistance deteriorates due to tin oxide growth
Solution Approach 1:
The patent applies heat treatment as a preliminary action before the Sn plating layer is exposed to service conditions. This pre-treatment forms a stable oxide layer in advance, preventing subsequent uncontrolled oxidation that would cause yellowing. The preliminary oxidation under controlled conditions prevents harmful oxidation during use.
Solution Approach 2:
The patent controls the oxidation process by adjusting heat treatment parameters (temperature, time, atmosphere composition). By optimizing these parameters, the oxidation is controlled to form a stable, protective layer rather than excessive or unstable oxide that would cause yellowing. The parameter control transforms a potentially harmful process into a beneficial one.
4Object-affected harmful factors
If no chromate treatment is applied to Sn-plated steel sheet, then environmental safety is improved, but sulphide stain resistance deteriorates
Solution Approach 1:
The patent removes chromate treatment from the process and replaces it with heat treatment that forms an oxide layer. This extraction eliminates hexavalent chromium while the oxide layer provides sulphide stain resistance through a different protective mechanism.
Solution Approach 2:
The heat treatment parameters are optimized to form an oxide layer with specific properties that provide sulphide stain resistance. By controlling temperature, time, and atmosphere, the oxide layer composition and structure are adjusted to resist sulphide staining, replacing the chromate-based protection with oxide-based protection.
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 significantly enhances yellow stain resistance, lacquer adhesion, and sulphide stain resistance without the need for conventional chromate treatment, maintaining the appearance and adhesion properties over time.
Implementation Method 1
growth of oxygen-deficient tin oxide
Implementation Method 2
peak position of binding energy of Sn3d5/2 according to X-ray photoelectron spectroscopy
Data Source
AI summary
The Sn-plated steel sheet of the disclosure is an Sn-plated steel sheet including: a steel sheet; an Sn plating layer formed on at least one side of the steel sheet and containing, based on % by mass, from 0.1 g/m2 to 15 g/m2 of metal Sn; and a coating layer formed on the surface of the Sn plating layer and containing zirconium oxide and tin oxide; in which the content of the zirconium oxide in the coating layer is from 0.2 mg/m2 to 50 mg/m2 in terms of metal Zr amount, and the peak position of binding energy of Sn3d5/2 according to X-ray photoelectron spectroscopy of the tin oxide in the coating layer is 1.6 eV or higher than the peak position of binding energy of the metal Sn.