1.What is the core function of anti-fingerprint treatment?
Anti-fingerprint: When a finger touches the zinc coating, sweat (containing salt and oil) will not directly contaminate the zinc coating, preventing difficult-to-remove marks and maintaining a clean surface (especially suitable for exterior components such as home appliances and electronics).
Enhanced corrosion resistance: The protective film blocks water and oxygen from contacting the zinc coating, delaying the formation of white rust (zinc oxidation products) and red rust (base iron corrosion), improving salt spray resistance by 30%-50%.
Improved processability: The film's lubricity reduces friction during stamping and prevents scratches on the coating. Some processes can also improve paint adhesion.
2.What are the principles and characteristics of chromate treatment?
Principle: Galvanized steel sheets are immersed in a solution containing chromate (hexavalent chromium or trivalent chromium). A chemical reaction forms a thin film of chromium compounds (such as zinc chromate) on the surface, approximately 0.5-2μm thick.
Features:
Advantages: Low cost, strong corrosion resistance (especially against white rust), and previously widely used.
Disadvantages: Hexavalent chromium is toxic and does not comply with environmental standards such as RoHS and REACH. Currently, it is only used in a few non-environmentally friendly applications. Trivalent chromium processes offer improved environmental friendliness but are more expensive.
3.What are the common types of chrome-free anti-fingerprint treatments?
Silane treatment: The hydrolyzed groups of silane molecules react with the zinc layer to form a covalently bonded siloxane film. This film offers excellent adhesion and corrosion resistance, is moderately cost-effective, and is suitable for applications in home appliances and construction.
Zirconium titanate treatment: Zirconium and titanium ions react with the hydroxyl groups on the zinc surface to form a dense oxide film. Its salt spray resistance approaches that of trivalent chromium treatment, and its environmental friendliness is excellent. It is commonly used in high-end electronics, photovoltaics, and other fields.
Organic resin composite treatment: A layer of acrylic or polyurethane resin is laminated onto the inorganic film layer to further enhance fingerprint and abrasion resistance. It is suitable for applications requiring high aesthetics, such as home appliance panels.
4.What are the characteristics of chrome-free anti-fingerprint treatment?
Environmentally friendly, no heavy metal contamination.
Fingerprint resistance is superior to traditional chromate treatments (fingerprints are easily wiped off).
Corrosion resistance is slightly lower than that of hexavalent chromium treatments, but through formula optimization, it can meet the needs of most applications (such as photovoltaic mounting systems and home appliances).
5.What are the application scenarios and performance requirements?
Home appliances (such as refrigerator side panels and washing machine casings): High fingerprint resistance and aesthetics are required. Organic resin composite chromium-free treatments are often used. The film must pass the "fingerprint wipe test" (using grease to simulate fingerprints, ensuring no residue remains after wiping).
Photovoltaic/new energy (such as brackets and battery casings): Corrosion resistance and environmental friendliness are prioritized. Zirconium titanate chromium-free treatments are commonly used. White rust must be eliminated after a salt spray test (neutral) of 500 hours or more.
Construction (such as ventilation ducts and decorative panels): Weather resistance is a priority. Silane treatment or trivalent chromium treatment may be used. Adaptability to outdoor temperature and humidity fluctuations is required.