Plasma electrolytic oxidation of metals

The results of investigation of the plasma electrolytic oxidation (PEO) process on some metals (aluminum, titanium, tantalum, magnesium and zirconium) were presented. The whole process involves anodizing metals above the dielectric breakdown voltage, when numerous micro-discharges are generated continuously over the coating surface. For characterization of the PEO process, optical emission spectroscopy and real-time imaging were used. These investigations enabled the determination of electron temperature, electron number density, spatial density of micro-discharges, the active surface covered by micro-discharges, and the dimensional distribution of the micro-discharges at various stages of the PEO process. Special attention was focused on the results of a study of the morphology, and the chemical and phase composition of oxide layers obtained in the PEO process on aluminum, tantalum and titanium in electrolytes containing tungsten. Physicochemical methods: atomic force microscopy (AFM), scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy served as tools for examining the obtained oxide coatings. In addition, the application of the obtained oxide coatings, especially the application of TiO2/WO3 coatings, in photocatalysis was discussed.