Characterization of oxide coatings formed on tantalum by plasma electrolytic oxidation in 12-tungstosilicic acid

► Oxide coatings are formed on tantalum by PEO process in 12-tungstosilicic acid. ► PEO process is divided into three stages according to change of voltage-time curve. ► Oxide coating morphology is strongly dependent of PEO time. ► Oxide coating is partly crystallized and mainly composed of WO3, Ta2O5 and SiO2. ► Outer layer of the coating is silicate tungsten bronze.