Abstract
The formation of cathodic films on zinc plated steel sheet by electrolysis of aluminum biphosphate solution was studied. The corrosion resistance of zinc plated steel was promoted remarkably by the formation of this conversion coated thin film. The film provides good protection against rusting and improves the adhesion of paint as well. The formation of the conversion film was considerably affected by variation in the current density during electrolysis and pH. The effects of electrolytic conditions, such as current density and pH, on the formation of cathodic films were determined by measuring the potential-time curves and corrosion resistance to salt spray. It was found that the film was formed at a pH above 2.4 and at a current density above 2A/dm2. The film formed on zinc plated steel sheet was found to possess a high formability.
