Effects of CeO2 on Microstructure and Corrosion Performance of the Coatings Prepared by Pulse Micro Arc Oxidation on AZ31B Mg Alloy

To improve corrosion performance of coatings on AZ31B magnesium alloy, the nano-CeO2 additives were included in Na2SiO3 based electrolyte during process of pulse micro arc oxidation (MAO). The MAO-CeO2 coating was successfully prepared to characterize its structure, micro morphology and composition. The XRD results indicated that MAO-CeO2 coatings were consisted of Mg2SiO4, MgSiO3, MgF2 and CeO2. The intensity of CeO2 peaks increases with increasing nano-CeO2 particles in electrolyte. The number of cracks on MAO-CeO2 coatings exhibited a V-shaped trend with increase in nano-CeO2 content. Meanwhile, the influence of nano-CeO2 on corrosion behavior of MAO-CeO2 coatings is investigated by salt spray test and electrochemical measurement. The corrosion current density of coatings presented same trend and corrosion potential is further studied. The MAO-CeO2 coatings formed in electrolyte with 10 g/L nano-CeO2 showed best corrosion performance which has the lowest corrosion current density of 0.58 nA/cm2 and the highest corrosion potential of - 1269 mVSCE.