Influence of the Electrical Parameters on the Fabrication of Oxide Layers on the Surface of Al-1050 by a Plasma Electrolytic Process

Oxide layers were prepared by an environmentally friendly plasma electrolytic oxidation (PEO) process on an Al-1050 substrate. The electrolyte for PEO was an alkali-based solution with Na2SiO3 (8 g/L) and NaOH (3 g/L). The influence of the electrical parameters on the phase composition, microstructure and properties of the oxide layers formed by PEO were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The voltage-time responses were recorded during various PEO processes. The oxides are composed of two layers and are mainly made of α-alumina, γ-alumina and mullite phases. The proportion of each phase depends on various electrical parameters. It was found that the surface of the oxides produced at a higher current density and Ia/Ic ratio shows a more homogeneous morphology than those produced with the electrical parameters of a lower current density and lowe