Abstract: Al2 O3/Ni composite coating was deposited on AZ 91D Mg alloy in two different proportions by electrophoretic deposition technique in order to improve the corrosion resistance of Mg alloy , and after dried for 12 h in a dry container , vacuum sintering densification process at 300 ℃ for 4 h is following. Surface morphology , compositions and microstructures of the coating were investigated using scanning electron microscopy(SEM), energy dispersive spectrometer (EDS) and X-ray diffraction(XRD) as well. Corrosion resistances of the coating were evaluated in 3.5wt; NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).The result showed that compared to the pure Al2O3 coating, the porosity of Al2O3/Ni composite coating decreases due to the addition of Ni , and the mismatch of thermal expansion coefficient of the coating and Mg alloy is reduced , and the bonding strength is enhanced .In the coatings of four different ratios , the composite coating with a mass ratio of Al2 O3 and Ni is 1:3.The surface of the composite coating more smooth and compact , and the corrosion resistance properties of the coating is better .

Key words: Al2 O3/Ni composite coating was deposited on AZ 91D Mg alloy in two different proportions by electrophoretic deposition technique in order to improve the corrosion resistance of Mg alloy , and after dried for 12 h in a dry container , vacuum sintering densification process at 300 ℃ for 4 h is following. Surface morphology , compositions and microstructures of the coating were investigated using scanning electron microscopy(SEM), energy dispersive spectrometer (EDS) and X-ray diffraction(XRD) as well. Corrosion resistances of the coating were evaluated in 3.5wt; NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).The result showed that compared to the pure Al2O3 coating, the porosity of Al2O3/Ni composite coating decreases due to the addition of Ni , and the mismatch of thermal expansion coefficient of the coating and Mg alloy is reduced , and the bonding strength is enhanced .In the coatings of four different ratios , the composite coating with a mass ratio of Al2 O3 and Ni is 1:3.The surface of the composite coating more smooth and compact , and the corrosion resistance properties of the coating is better .