Characteristics of plasma electrolytic oxidation coatings on 6061 al alloy prepared at different current densities

Abstract

Plasma electrolytic oxidation (PEO) has earned much attention due to its powerful and easy formation of hard and corrosion-resistant oxide layers on valve metals, such as Al alloys. Here we report the effects of current density (CD) on microstructure and properties of coatings on 6061 Al alloy by PEO using direct current mode. The electrolyte contains the chemicals of Na₂ SiO₃ , Na₂WO₄ x 2H₂O, and NaH₂PO₂ x H₂O. The CDs adopted 5.0, 7.5, 10.0, and 12.5 A/dm², respectively, for a fixed PEO time of 30 min. The thickness, surface morphology, phase composition, hardness, and corrosion resistance of PEO coatings as a function of the applied CD have been studied and discussed.