Effects of Nickel Additive on Micro-Arc Oxidation Coating of AZ63B Magnesium Alloy

摘要

Based on environmentally friendly and green manufacturing of magnesium alloys, micro-arc oxidation coatings were prepared in optimized metasilicate solutions on AZ63B magnesium alloys surfaces. Effect of nickel additive on working voltage, surface morphology, thickness, hardness, composition and corrosion resistance of micro-arc oxidation coating of magnesium alloys was studied. The surface morphology, composition, microstructure and corrosion resistance of conversion coatings were investigated by using scanning electron microscopy (SEM), energy dispersion spectrometry (EDS), X-ray diffraction (XRD) and electrochemical tests respectively. The results show that brown coating was prepared in electrolyte with the addition of nickel acetate, which can accelerate growth of micro-arc oxide film layer and make the smaller hole on the surface. The micro-arc oxide coating mainly consists of Mg2SiO4, MgSiO3, MgAl2O4, Ni2SiO4. Potentiodynamic measurements and electrochemical impedance spectroscopy (EIS) testify that the corrosion resistant of micro-arc oxidation film adding nickel acetate electrolyte increases significantly.