Effects of Current Mode on Porosity and Corrosion Resistance of Micro-arc Oxidation Ceramic Coating on Mg-Zn-Ca Magnesium Alloy
Three kinds of micro-arc oxidation coatings were prepared on Mg-Zn-Ca alloy substrate by using unipolar,bipolar and hybrid mode.The surface pore and surface morphology of the coating were measured by scanning electron microscope and 3D laser scanning confocal microscope,respectively.X-ray diffractometer was used to analyze the phase structure of the coating.The corrosion resistance of three kinds of coatings was studied by electrochemical workstation and 500h salt spray corrosion experiment.The results show that the three coatings are mainly composed of MgO,Mg2SiO4 and Mg2SiO3 phases.The coating obtained under hybrid mode has better surface finish and the size of surface pore is(5.52±0.63)μm.Besides,the low porosity has a barrier effect,which makes the coating has a better corrosion resistance than those in unipolar and bipolar modes.
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