Research on AC corrosion behavior and corrosion product film evolution of X70 steel under the combined action of AC interference and CP

Corrosion behavior and corrosion product film evolution under AC interference and CP were investigated by corrosion tests. High CP AC corrosion could be identified according to corrosion rate map. In case of high CP AC corrosion, corrosion products gradually grew into compete film to provide protection, and subsequently it was destroyed and re-built during two successive stages in cyclic pattern. This pattern was tentatively attributed to the interplay of destructive action of cathodic reaction processes and AC electric field upon protective film, together with constructive action of anodic reaction processes leading to recovery of protective film upon bare metallic surface.