The effect of argon ion etching treatments on anodic oxide film growth and the electrochemical properties of tantalum

The aim of present paper was to improve the anticorrosive properties of tantalum. Herein, the formation of tantalum oxide film via an argon ion etching pretreatment step and anodic oxidation is reported. The surface morphologies of etched tantalum investigated using scanning electron microscopy. The composition and corrosion resistance of the tantalum oxide film was characterized using X-ray photoelectron spectroscopy and an electrochemical workstation, respectively. The effects of vacancy defects and O atom adsorption on the on Ta (110), (200) and (211) surfaces have been investigated based on first-principles calculations to simulate the etched surface. The experimental results showed that the etched tantalum had a relatively clean surface with fine pores, which promoted the formation of an anodization film to 131.53 nm. The corrosion resistance of tantalum was obviously improved by etching followed by anodization, and the highest corrosion potential of 0.133 V and relatively low corrosion current density of 1.016 μA cm–2 were observed. Furthermore, first principle calculations revealed that vacancy defects increased the activity of the tantalum surface and enhanced the adsorption of oxygen, thereby promoting the formation of oxide film. Among all these defective surfaces, O atom adsorption on the (110) surface exhibited relatively a high adsorption energy of −519.66 kJ/mol and charge transfer of −1.310 e, followed by O atoms on the (200) and (211) surfaces showing an enhanced adsorption energy of −487.33 and −494.27 kJ/mol, and charge transfer of 1.255 and 1.194 |e |, respectively. This work demonstrated an effective argon ion etching pretreatment step to promote the formation of oxide film, which improved the corrosion behavior of tantalum.