Pitting Behavior and Pit Morphology of Anodic Oxide Film On Three Aluminum Alloys

摘要

Pitting corrosion behaviors of anodized film on three aluminum alloys, 1070, 2024 and 7075, in NaCl solutions were studied using methods of potentiodynamic polarization and SEM and EDXA. Pitting corrosion happened for all the three anodized films in neutral, acidic and basic 1 M NaCl solutions. The polarization currents showed stepwise increases. Pitting corrosion resistance of the anodized film for 1070 alloy increased with increase of the film thickness, but film thickness had little influence on corrosion resistance of the films on 2024 and 7075 alloys. For 1070 alloy, once a pit penetrated the film, it developed preferentially under the film, resulting in deep pit with small mouth. For 2024 and 7075 alloys, the pits intended to grow across the film and big and sallow pits were formed. Different alloying elements in the alloys were responsible for the differences in corrosion behaviors of the anodized films.