Self-healing performance and corrosion resistance of phytic acid/cerium composite coating on microarc-oxidized magnesium alloy

Self-healing protective coatings have attracted increasing attention as an efficient way for maintaining the performance of protection of the underlying substrate and extending substrate lifetime. Herein, we report a facile and green approach to prepare phytic acid/cerium composite coating (PA/Ce) with self-healing ability on microarc-oxidized magnesium alloy by hydrothermal treatment. Natural non-toxic phytic acid was used as an intermediate chelating agent to enhance the bonding strength between cerium salt particles and Micro-arc oxidation (MAO) layer. The morphology, cross-sectional structure, composition, self-healing property and mechanism were comprehensively investigated. The results showed that the as-prepared MAO/PA/Ce composite coating with a thickness of about 5 μm was dense and homogeneous, which bonded well with the AZ31B substrate. Electrochemical tests indicated that the MAO/PA/Ce composite coating significantly increased the corrosion resistance of the AZ31B substrate. Moreover, the composite coating showed self-healing behavior and could provide long-term corrosion protection for the substrate. The self-healing process and mechanism for the composite coating were proposed.