Steel Sheet Chemical Conversion Coating for Containers
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Solution Overview
Problem
Steel sheets for containers face challenges in achieving excellent film adhesion and external properties, particularly in the neck portion of cans, while maintaining corrosion resistance without chromate treatment, and require improved aesthetic appearance with brighter color tones.
Innovation Solution
A steel sheet with a chemical conversion coating layer containing zirconium, phosphoric acid, and phenolic resin coatings, applied on a nickel or tin plating layer, ensuring specific particle size ratios and amounts to enhance adhesion and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromate treatment is applied to steel sheets for containers, then corrosion resistance and adhesion to paint/film are enhanced, but environmental harm increases due to hexavalent chromium
Solution Approach 1:
The invention extracts and eliminates the harmful hexavalent chromium component from the chromate treatment process while retaining the essential functional benefits. The patent develops alternative surface treatment methods using non-chromate chemicals that form conversion coatings on steel sheets, achieving corrosion resistance and adhesion properties without environmental contamination.
Solution Approach 2:
The invention replaces the persistent harmful chromate coating with alternative coating materials that can be applied as thin, effective layers. These alternative coatings use environmentally friendly chemicals that form sufficient protective layers without the long-term environmental persistence and toxicity of hexavalent chromium.
2Reliability
If chromate treatment is applied to steel sheets for containers, then adhesion to paint and film is enhanced, but environmental harm increases
Solution Approach 1:
The invention extracts the adhesion-enhancing functional properties of chromate treatment while removing the harmful hexavalent chromium. Alternative conversion coatings using zinc, iron, or aluminum-based chemicals are developed to provide equivalent or superior adhesion to paint and film without environmental damage.
Solution Approach 2:
The invention introduces intermediary substances such as zinc phosphate, iron phosphate, or aluminum-based conversion coatings that serve as intermediate layers between the steel sheet and the paint/film. These intermediary coatings provide the necessary adhesion promotion and surface preparation functions previously achieved by chromate, but without the environmental harm.
3Object-affected harmful factors
If conventional surface treatment is applied to replace chromate, then environmental harm is reduced, but film adhesion in the neck portion deteriorates
Solution Approach 1:
The invention applies local quality control by optimizing the surface treatment parameters specifically for the neck portion of containers where film adhesion is most critical. The patent develops controlled conversion coating processes that create locally enhanced surface properties in high-stress areas like the neck portion, ensuring adequate film adhesion under necking conditions while maintaining environmental compatibility.
Solution Approach 2:
The invention employs parameter changes in the surface treatment process, such as controlling coating thickness, surface roughness, and chemical composition within specific ranges to optimize film adhesion. By adjusting these parameters, the patent achieves sufficient adhesion strength in the neck portion without requiring harmful chromate treatment.
4Reliability
If surface treatment is applied to improve film adhesion, then adhesion increases, but external appearance and color tone deteriorate
Solution Approach 1:
The invention applies local quality by differentiating surface treatment between functional areas (where adhesion is critical) and aesthetic areas (where appearance is critical). The patent develops selective surface treatment methods that provide enhanced adhesion properties only where needed, while maintaining smooth, bright surfaces on visible exterior areas for optimal print quality and aesthetic appearance.
Solution Approach 2:
The invention uses parameter changes to control the balance between adhesion and appearance. By precisely controlling conversion coating thickness, surface roughness, and chemical composition within specific ranges, the patent achieves sufficient film adhesion while maintaining smooth surfaces that provide bright color tones and excellent external appearance for high-quality printing.
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 excellent film adhesion, corrosion resistance, and improved external properties, including a brighter color tone, while replacing chromate treatment, thus addressing market competition and consumer preferences.
Implementation Method 1
a chemical conversion coating layer including at least two kinds of coatings selected from the group consisting of a zirconium coating containing a given amount of zirconium, a phosphoric acid coating containing a given amount of phosphoric acid, and a phenolic resin coating containing a given amount of phenolic resin
Data Source
AI summary
Disclosed is a steel sheet for containers that maintains excellent corrosion resistance even when a surface treatment that replaces a chromate treatment has been conducted, and that has excellent film adhesion qualities and appearance. This steel plate for containers has, on at least one surface thereof, a chemical conversion coating including at least two coatings selected from a zirconium coating that contains zirconium and has a metal zirconium content of 0.1-9 mg/m2, a phosphate coating that contains phosphoric acid and has a phosphorous content of 0.1-8 mg/m2, and a phenolic resin coating that contains phenolic resin in an amount of 0.5-8 mg/m2 in terms of carbon, the percentage of the area of the surface of the chemical conversion coating layer having particles Of a prescribed size being 0.1-50%.