Effect of chemical composition of electrolyte on corrosion resistance of PEO coating on AZ31 magnesium alloy

Plasma electrolytic oxidation was employed to form a ceramic-based coating on magnesium AZ31 alloy. The electrolytes used for the PEO processes were silicate-based electrolytes with different concentrations of phosphate. The morphologies and cross-sections of the coatings were examined with scanning electron microscopy (SEM), and the defects of the coatings and their thicknesses were measured by Image J software. The corrosion resistance of the coatings was evaluated by electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The results showed corrosion resistance of the coating with 6 g/L three sodium phosphate was the best.

Keywords:

Plasma electrolytic oxidation , magnesium AZ31 , EIS