In order to solve the problems of poor corrosion resistance of high rare earth magnesium alloy

the surface treatment of magnesium alloy was performed by micro-arc oxidation to improve its corrosion resistance.For the micro-arc oxidation process adopted

based on analysis

the step-down method was used to control the process parameters

and the orthogonal test of each parameter of the electrolyte was analyzed.The ratio of the corrosion area obtained by the neutral salt sprayed testing and the thickness of the film observed by the metallographic phase were used as indicators to obtain the optimized electrolyte parameters.The thickness

phase composition and surface morphology of each group in the orthogonal experiment were analyzed by OM

XRD and SEM.The results reveal that when the voltages of each stage are 550 V

500 Vand 450 V

respectively（using the voltage control system under the step-down method）

with the negative voltage of 250 V

the duty ratio of 20% and the oxidation time of 50 min

the optimized electrolyte parameters can be obtained by range analysis:sodium silicate of 20 g/L

sodium tetraborate of 40 g/L

NaOH of 20 g/L

triethanolamine of 15 ml/L

nickel acetate of 0.12 g/L

a complexing agent（sodium citrate）of 15 g/L

where odium silicate presents the most importance.The film analysis by XRD and ED reveals that the film is mainly composed of the spinel phase Mg

2

SiO

4

cubic structure of MgO

MgSiO

3

MgCO

3

and Ni

2

O

3

as well as a small amount of Na

Gd and other elements.