Enhancing corrosion resistance of magnesium alloy by rGO/Mg(OH)2 composite coating

rGO/Mg(OH)2 composite films were fabricated on AZ61 alloy by the hydrothermal method in alkaline solutions containing deionized water and graphene oxide (GO). During the hydrothermal reaction, the Mg(OH)2 nanosheets and GO plates grew freely on the AZ61 substrate without any special orientation, and the GO was simultaneously reduced to rGO. With the increase of GO content in the hydrothermal solution, the corrosion resistance of the prepared composite films showed a trend of increasing first and then decreasing. When the content of GO incorporated in the hydrothermal solution is 5 mg, the corrosion current density (icorr) of the composite coating is reduced to the minimum (4.9 μA/cm2), which is seven times lower than that of the substrate and 3.5 times lower than that of the Mg(OH)2 monolayer. Based on experimental and molecular dynamics simulation results, the enhancement mechanism of the composite film was proposed, which is related to the growth of Mg(OH)2 layer, the “tortuous path” effect of GO and the slowing of chloride ion diffusion by GO functional groups.