Special Features of Oxide Layer Formation on Magnesium Alloys during Plasma Electrolytic Oxidation

The process of the oxidation of magnesium alloys in a silicate electrolyte during plasma electrolytic oxidation is investigated. An anomalous form of the chronogram of the formation voltage of the oxide layer in the electrolytes with the highest silicate concentration (approximately 0.15 M Na₂SiO₃ · 5H₂O) is detected. X-ray diffraction analysis, scanning electron microscopy with energy dispersive X-ray spectroscopy analysis, and thickness gauges are used to characterize the surface microstructure, phase composition, and thickness, respectively. Mechanisms for the initial period of PEO and the “insular” growth were described. During the “insular” growth, islands consisting of vitrified components of the electrolyte are growing on the original smooth surface.