Investigation on the effect and growth mechanism of two-stage MAO coating

As a more popular surface treatment method, micro-arc oxidation technology can well solve the problems of insufficient strength and poor corrosion resistance of aluminum alloy surface. In this paper, a composite coating was obtained by using a two-stage micro-arc oxidation method different from the conventional micro-arc oxidation treatment, which solved the problem of incompatibility between the two types of electrolytes and obtained a coating with superior effect. The microscopic morphology and elemental composition were characterized by using Energy Dispersive Spectrometer (EDS)/X-ray Diffraction (XRD)/Scanning Electron Microscopy (SEM). The coating thickness was tested using a coating thickness gauge, its tribological properties were tested by friction experiments, and its corrosion resistance was tested by electrochemical corrosion tests. The results show that the coating has the advantages of large thickness, dense, good anti-wear performance, small friction coefficient and excellent corrosion resistance, which enhanced the performance of MAO coating and was an important guide for further work. [Display omitted] •The inability of MAO coating to combine the advantages of both electrolytes was solved by using two-stage treatment.•Two-stage MAO treatment can obtain a thicker, more uniform and denser coating with lower energy consumption.•The two-stage MAO coating was found to have excellent wear resistance and low friction coefficient.•The two-stage MAO coating has greatly improved the corrosion resistance of aluminum alloy substrate.