Electrochemical method to evaluate the healing process of the film formed on steel part of cut edge of prepainted 55%Al-Zn steel sheet with inorganic anti-corrosion pigments and the dissolution property of hot dip galvanized Al-Zn part of cut edge was developed. Anti-corrosion properties of the film formed on steel part and hot dip galvanized Al-Zn part of the cut edge were separately evaluated by analyzing of polarization curves of specimens in 5%NaCl solution. The optimum potentials to compare the ability to inhibit the reduction reaction of hydrogen ion and oxygen by the film formed on steel part of cut edge and anodic dissolution of hot dip galvanized Al-Zn part of cut edge were determined, and then the healing process of the film could be quantitatively compared. Corrosion tests of cut edge of prepainted 55%Al-Zn steel sheet with various types of anti-corrosion pigments were conducted. The difference of the healing process by anti-corrosion pigments was analyzed using electrochemical measurement and EPMA, and it was revealed that the healing ability of vanadate acid anti-corrosion pigments is nearly equal to the conventional chromate pigments.
This study aims at the representation of carbon-aluminium galvanic corrosion under a saltwater film environment. In the numerical simulation, multiphysics problems including electric field, electrophoresis, mass diffusion, chemical reactions and moving boundaries are taken into account. In the mass transport analysis, the simulator is speeded up by using an implicit method. In the chemical reaction analysis, distribution of pH and precipitation is accurately represented by considering 4 chemical reactions of aluminium ions. Additionally, the simulator is validated through galvanic corrosion experiments.