Modification of tantalum surface via plasma electrolytic oxidation in silicate solutions

Herein, an investigation of the anodic oxidation process of pure tantalum metal in a solution composed of potassium silicate (K2SiO3) and potassium hydroxide (KOH) under different voltage conditions is reported. The selected process voltages were 100, 200 and 400 V. Anodic oxidation conducted below the dielectric potential of the metal oxide did not alter the surface morphology, whereas the process carried out at a voltage of 400 V led to the development of a highly porous structure, which is typical of plasma electrolytic oxidation (PEO). A significant amount of electrolyte ions, especially Si species, was observed in the case of the PEO treatment of tantalum. Silicon was present in the forms of silica and silicate species, with silica being the dominant form. Anodisation under specific conditions was shown to markedly improve the corrosion performance of tantalum in Ringer's simulated body fluid.