High Anti-corrosion Chromic Acid Anodizing Process

A chromic acid anodizing (CAA) process for aluminum alloys used in aviation was investigated by testing the thickness, adhesion and corrosion resistance of the film. The results showed that alloy components had great effect on the thickness of oxide films and all films were thicker than 2 μm. After sealing in potassium bichromate, the oxide film formed on 2024-T3 aluminum alloy met the requirements of 750 h salt spray test, and the adhesion between the oxide film without sealing and the paint layer was excellent. The lower the concentration of Cr3+ in chromic acid anodizing bath, the better the corrosion resistance of oxide film. The corrosion resistance of oxide film could be improved by sealing the oxide film immediately after formation. The chromic acid anodizing process for aluminum alloys has been applied to production.