The evaluation of plasma electrolytic oxidation properties on car compartments made with Mg alloy

In recent years, the automotive industry has expanded its usage of magnesium alloys because to their favorable metallurgical properties. It is, however, vital to coat the magnesium components like piston in the car engines because of their harsh working environment. In this study, beyond the introduction of novel plasma electrolytic oxidation coating for AZ31 Mg alloy, the metallurgical characteristics of coating generated in silicate and aluminate electrolytes are also examined. Phase studies revealed that along with the presence of MgF2 and MgO in both coating, Mg2SiO4 and MgAl2O4 were discovered in coatings created in silicate and aluminate electrolytes, respectively. The application of PEO resulted in a considerable drop in corrosion rate, such that the corrosion rate of the coating formed in silicate electrolyte is 2.24×10-6 A.cm-2 and that of the coating created in aluminate electrolyte is 9.5×10-7 A.cm-2, which are 30 and 68 times lower than the rate of uncoated samples, respectively. Additionally, as compared to the uncoated sample, the coating enhances the surface electrical resistance by 72 and 94 times. The microscopic analysis showed that the average diameter of porosities in PEO coating made by silicate electrolyte is higher than that of coating made by aluminate electrolyte