Abstract:Porous ceramic layers were prepared on AZ31B magnesium alloy by Micro-arc Oxidation (MAO), and then electrophoretic coat (E-coat) was deposited on MAO coated Mg alloy. The surface roughness, surface and cross section morphologies, electrochemical properties and scribed corrosion properties of the MAO layer and MAO composite electrophoretic (MAOE) coating were studied. The results indicate that the discharge channels on surface of MAO layer are completely covered by E-coat and the surface of MAOE coating is very smooth; as a result, the surface roughness decreases obviously. The corrosion current density of MAOE coating is two and four orders of magnitudes lower than that of MAO layer and bare Mg alloy, respectively, and the polarization resistance is two and four orders of magnitudes higher, respectively, suggesting that the corrosion trend decreases. The EIS resistance of MAOE coating is four orders higher than that of MAO layer while the EIS capacitance is four orders lower, and thus the corrosion resistance is improved uncommonly. Due to the mechanical interlock between the MAO layer and E-coat, the substrate is corroded seriously during scribed corrosion test, and the coating delaminating at the interface of MAO layer and substrate also occur. However the interface of MAOE composite coating is still compact.