Improvement of Corrosion Resistance of 7075 Aluminum Alloy by Micro Arc Oxidation after Hole Sealing Treatment

Aluminum alloys are widely used in aerospace and marine transportation industries because of their excellent properties. However, the aluminum oxide film on the surface of aluminum alloy in service is easy to be damaged by corrosive media, resulting in matrix corrosion cracking, which also hinders the wide application of aluminum alloy in more fields. In this paper, the PEO/SOT composite coating was prepared by plasma electrolytic oxidation (PEO) combined with surface oiling treatment (SOT). Oiling treatment can effectively cover the discharge channels and cracks on the PEO surface, so as to prevent corrosive ions from contacting through the coating and damaging the aluminum alloy matrix. The corrosion resistance of the composite coating was tested by electrochemical workstation. The results show that PEO/SOT composite coating has better corrosion resistance in corrosive environment than the substrate and PEO coating. This will help to expand the application of aluminum alloy in the field of higher requirements.