The effects of carbon-based additives on corrosion and wear properties of Plasma electrolytic oxidation (PEO) coatings applied on Aluminum and its alloys: A review

Although aluminum and its alloys are typically utilized like lightweight materials in a lot of industries, they suffer from low corrosion and wear resistance as well as low hardness. Fortunatly, using surface modification procedures including plasma electrolytic oxidation (PEO) technique, these matters can be resolved. In this technique, uniform, thick, hard, wear- and corrosion-resistant, and highly adherent coatings can be produced. Being a key factor, the usage of distinct solutions in the PEO procedures can result in structure, composition, and distinct properties in coatings. One of the benefits of PEO procedures is to add various additives into the solutions and create the coatings having favorable properties. Owing to the significant properties of carbon allotropes such as carbon nanotubes, graphite, diamond, and graphene, they can be an appropriate option in order to boost the PEO coatings properties. These additives can decrease the penetration and rate of corrosive ions into coatings by contributing and absorbing these additives in PEO coatings and as a result declining the number and size of cracks or pores and raising the thickness and density of coatings and so increase corrosion protection. From the view of wear, raising the density and hardness of coatings on account of these additives or in some cases the self-lubricating properties of additives results in improving the wear resistance. Thus, in this study, we have reviewed the carbon allotropes' effects on the corrosion and wear characteristics of PEO coatings applied on aluminum and its alloys.