Plasma electrolytic oxidation of AZ31 Mg alloy in bipolar pulse mode and influence of corrosion to surface morphology of obtained coatings

Abstract

PEO method was used with AZ31 Mg alloy plates for improving corrosion resistance of the alloy. Process parameters for the PEO setup were optimized by studying the effects of KOH concentration, operating voltage, and pulse properties on the obtained coating. These conditions were then used to produce PEO coated AZ31 specimen and were tested by immersion in 3% NaCl solution for 1 week. Three types of modifiers were used in the electrolyte and concentrations of the modifiers were varied to study the effect of concentration on the performance of coating obtained. Extent of corrosion was visually examined, and it was found that an electrolyte recipe with all three modifiers produced the best results.