Design and in situ prepare a novel composite coating on Mg alloy for active anti-corrosion protection

In this paper, a novel composite coating combining Layered Double Hydroxides (LDH) film and Micro-arc Oxidation (MAO) ceramic layer was designed to further enhance anti-corrosion protection of coating. The MgFe-LDH/MAO composite coating was prepared through in situ synthesis MgFe-LDH nanoflakes on the surface of MAO coating. Subsequently, the active anti-corrosion mechanism of MgFe-LDH layer was revealed through microstructure characterization and electrochemical test. Furthermore, the interaction between LDH nanoflakes and original MAO coating was investigated, too. The results show that: LDH nanoflakes preferentially grow in the pores of original MAO coating, and form a dense layer on MAO coating. In situ prepared LDH layer gives a strong and stable adhesion on MAO coating, besides the dissolution of original MAO coating affects LDH growth. MgFe-LDH layer supplied an active anti-corrosion protection for Mg alloy, since LDH can effectively seal the inherent defects of MAO coating and absorb corrosive medium in environment.