Study of the effect of Pyrophosphate in low voltage Plasma Electrolytic Oxidation on the corrosion resistance of AZ31B Magnesium alloy

In this study, low voltage Plasma Electrolytic Oxidation (PEO) was utilized to eliminate the drawbacks of high voltage PEO such as high cost, dimensional deformation, and porosity. Low voltage PEO produces a thin coating, which leads to low corrosion resistance. In order to solve this problem, 0.1 similar to 0.6 M pyrophosphates were added to a bath containing 1.4 M NaOH and 0.35 M Na2SiO3 center dot PEO at 70Vwas conducted at 25 degrees C for 3 minutes. The chemical composition, morphology, and corrosion resistance of the anodized coating were analyzed. The anodized film was composed of MgO, Mg2SiO4, and Mg2O7P2. Themorphology of the film showed a inappropriately dense structure and low porosity in the anodized layers. It is found that low voltage Plasma Electroly tic Oxidation in cooperation with phosphating treatment can provide good corrosion protection for the AZ31B magnesium alloy.