Localized electrochemical impedance spectroscopy study on the corrosion behavior of Fe-Cr alloy in the solution with Cl ^- and SO ₄ ^2-

The corrosion behaviors of Fe-Cr alloy under three different pH values solutions with Cl ^- and SO ₄ ^2- were investigated by localized electrochemical impedance spectroscopy (LEIS) measurements and the corrosion products were analyzed by laser Raman spectrometry. The results show that the high corrosion resistance of Fe-Cr Alloy is attributed to a passive film which is formed more easily when the alloy contains a large quantity of Cr element. However, its corrosion resistance varies in the solutions with different pH values, especially in the initial corrosion. The average impedance values in neutral and alkaline solution are much higher than that in acidic solution because the passive film is more likely to dissolve in the acidic condition. Moreover, the destructive effect of Cl ^- and SO ₄ ^2- ions on the passive film is also demonstrated in corrosion process through the change of the impedance value with the steeping time.