Self-Healing Coatings Prepared by Loading Interphase Inhibitors into MAO Coating of AM60 Mg Alloy

A type of self–healing coating for AM60 Mg alloy was prepared by loading interphase inhibitors into micro–arc oxidation (MAO) coating. The effects of inhibitor species, impregnation methods, and MAO status on the self–healing properties of the coatings were studied using electrochemical impedance spectroscopy, scanning electron microscopy, and X–ray photoelectron spectroscopy. The results showed that, among the three selected inhibitors, Na 3 PO 4 is the most efficient inhibitor as it forms a long–lasting protective product film Mg 3 (PO 4 ) 2 in the scratched areas. In comparison with atmospheric impregnation, vacuum impregnation can efficiently load inhibitors into MAO pores both in quantity and depth. Although the large size of MAO pores is harmful to the corrosion resistance of MAO coating, it is beneficial for the self–healing properties owing to the easy loading of inhibitors.