Microarc oxidation of 2024 Al alloy using spraying polar and its influence on microstructure and corrosion behavior

Spraying microarc oxidation (SMAO) equipment, consisting of a mini microarc oxidation (MAO) power source and a movable spraying polar, was employed to solve the problem that field repair of local damage area on workpiece and larger workpiece cannot be immersed in the electrolyzer for conventional microarc oxidation (CMAO) process. SMAO coatings were fabricated on the surface of 2024 Al alloy samples using a self-made SMAO equipment system. Electrochemical techniques were employed to evaluate the corrosion resistance of CMAO and SMAO coatings in 3.5 wt.% NaCl solution. The results indicated that SMAO coating is thinner than CMAO coating under the same experimental conditions. SMAO coating treated for 10 min can be easily penetrated by the test solution, while treated for 20 and 30 min, the coatings with much better corrosion resistance can be fabricated.