A ceramic coating on 5083 aluminum alloy was prepared by micro-arc oxidation （ MAO） in silicate solution

and the growth curve of the coating was drawn.The morphology

composition and phase constituent of the MAO coating were analyzed. The corrosion properties of 5083 aluminum alloy sample before and after the MAO surface treatment were evaluated by salt spray corrosion test

potentiodynamic polarization curves and electrochemical impedance spectroscopy （EIS）. In the initial stage

the current density is dropped rapidly and the coating is grown mainly towards the outer surface

and the surface roughness of the coating is increased rapidly. More than 30 min

the current density is decreased slowly and the coating is grown gradually towards the inner layer of coating. The MAO coating on 5083 aluminum alloy consists of γ -Al2O3 and a small amount of mullite （3A2O3·2SiO2） phases

and the mullite mainly appears in the outer layer of coating. Moreover

by microarc oxidation surface treatment

the corrosion current density of 5083 aluminum alloy is decreased by about two order degree of magnitude

and its electrochemical impedance modulus |Z| is obviously increased

improving significantly the corrosion resistance of coated 5083 alloy. In addition

the fitting analysis of EIS shows that the corrosion resistance of the MAO coating is controlled by the compactness of inner layer.