Improving the wear resistance of plasma electrolytic oxidation (PEO) coatings applied on Mg and its alloys under the addition of nano- and micro-sized additives into the electrolytes: A review

As an efficient surface modification approach, the plasma electrolytic oxidation (PEO) technique can boost the capability of wear protection in Mg and its alloys by applying a hard and thick ceramic coating. In this procedure, more efficient protection can be acquired via adding additives (in the form of particle, powder, sheet, etc.) into solutions and producing composite coatings. These additives result in more efficient protection against wear via getting stuck in the cracks and pores of coatings and rising the thickness, hardness, and diminishing the porosity size and content. The efficiency of each additive can be changed owing to its intrinsic properties like melting point, size, participation type (reactive, partly reactive, or inert) and potential of zeta. In this review, the effects of distinct additives in nano- and micro-scale size on wear behavior of PEO coatings on Mg and its alloys is going to be reviewed.