Properties of aluminum alloy anodic films formed in three kinds of solutions

The properties of anodic films formed in chromic, boric-sulfuric and adipic-sulfuric acid (CAA, BSAA and ASAA, respectively) on LY12 aluminum alloy were studied by morphology characterization, current-voltage response test, electrochemical impedance spectroscopy (EIS) and fatigue test methods. It is indicated that in contrast with BSAA film, CAA and ASAA films have less defects and a smoother periphery. All of three kinds of anodic films have perfect corrosion resistant after immersed in 5% NaCl solution for 80 d. The resistance value (Rb) of the barrier layers of BSAA decreases in greatest, while the Rb values of CAA and ASAA decrease by 75% and 78%, respectively. From fatigue test results, it is confirmed that CAA reduces the fatigue life of the matrix at a little, about 14%, ASAA, about 20%, and BSAA about 25%, indicating that BSAA has the greatest impact on the fatigue life of the matrix among the three treatments.