Role of anodic oxide films in the corrosion of aluminum and its alloys

Anodic oxide films on aluminum are classified into two groups: porous-type anodic oxide films (PAOF) and barrier-type anodic oxide films (BAOF). The present paper is a review of the corrosion of pure aluminum (Al) and Al alloys covered with PAOF and BAOF, focusing on the role of anodic oxide films in the process of corrosion. Several topics are discussed in detail, including (a) changes in the dissolution mode of PAOF in acidic media by pore sealing, (b) hydration and dissolution of BAOF in pure water and neutral solutions containing organic and inorganic electrolytes, (c) pitting corrosion during the cathodic polarization of Al covered with PAOF and BAOF, (d) corrosion of PAOF-covered Al/ Bi/ Sn alloys in alcohols at 142 degrees C, and (e) synergistic effects of Cl- and Cu2+ ions in the corrosion of PAOF-covered Al alloys in aqueous solutions.