Microstructure and Corrosion Behavior of MAO-SG Composite Coating on 7075 Aluminum Alloy.

To improve the corrosion resistance of 7075 aluminum alloy microarc oxidation (MAO) coating, graphene of 3 g/L was adsorbed and deposited in the coating. Then, the microarc oxidation–sol–gel (MAO-SG) composite coating was obtained by sealing the micropores of the coating with TiO₂ sol–gel. Electrochemical tests of 7075 aluminum alloy matrix, undoped sample, doped graphene sample and sealed sample were carried out in 3.5wt.% NaCl solution. The results show that compared with the blank sample, the self-corrosion potential of the sealed sample is increased by 98.1%, and the self-corrosion current density is reduced by 4 orders of magnitude. After immersion corrosion for 720 h, the corrosion rate of MAO-SG composite coating is 3.4 × 10^–5 mm/a, and its corrosion resistance is still better than that of single MAO coating. This is due to the strong conductivity of graphene and the blocking effect of TiO₂ sol–gel. [ABSTRACT FROM AUTHOR]