Influence of pH on Electrochemical Behaviors of Hot-dip Galvanized Auto Steel Sheet and IF Substrate in NaCl Solutions

Electrochemical behaviors of the hot-dip galvanized auto steel sheet and IF (interstitial-free) substrate were investigated by means of EIS and polarization curves in NaCl solutions with various pH values.The results showed that the corrosion process of the galvanized steel sheet was mainly controlled by charge transfer process,but corrosion of the IF substrate was controlled by the diffusion process of oxygen and hydrogen ions in the solutions.The galvanized steel presented a higher corrosion rate than the IF steel substrate,but the corrosion evolution tendencies were similar.With increasing the pH value the charge transfer resistance increased,and thus the corrosion current density decreased,i.e.,the corrosion rate decreased gradually.