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 AZ۳۱ 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 MgF۲ and MgO  in both coating, Mg۲SiO۴ and MgAl۲O۴ 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 ۲.۲۴×۱۰-۶ A.cm-۲ and that of the coating created in  aluminate electrolyte is ۹.۵×۱۰-۷ A.cm-۲, which are ۳۰ and ۶۸ times  lower than the rate of uncoated samples, respectively. Additionally, as  compared to the uncoated sample, the coating enhances the surface  electrical resistance by ۷۲ and ۹۴ 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.

Keywords:

Plasma electrolytic oxidation , Magnesium alloy , Piston , Corrosion , اکسیداسیون پلاسمای الکترولیتی , آلیاژ منیزیم , پیستون , خوردگی