Beneficial effect of 4% Ta addition on the corrosion mitigation of Ti–12% Zr alloy after different immersion times in 3.5% NaCl solutions

Abstract

The recent study reports the fabrication and corrosion behavior of two Ti alloys, 88% Ti–12% Zr and 84% Ti–12% Zr–4% Ta, in 3.5% NaCl electrolyte. These alloys were manufactured using powder metallurgy, where the powders were mixed, ball milled, and sintered. The corrosion behavior of these alloys was examined using various electrochemical and spectroscopic tests. Cyclic polarization experiments indicated that adding 4% Ta reduces corrosion of the TiZr alloy by suppressing anodic dissolution, resulting in a lower corrosion rate. The Nyquist and Bode impedance spectra for the tested alloys revealed that the presence of 4% Ta within TiZr alloy highly decreases the corrosion by increasing the impedance of the interface, the maximum degree of phase angle, and polarization resistance. The chronoamperometric current measured at −0.10 V (Ag/AgCl) proved that the presence of 4% Ta powerfully alleviates both uniform and pitting corrosion for TiZr alloy by lowering the obtained absolute currents. The surface investigation using scanning electron microscopy confirmed the homogeneity of the surfaces. The elemental analysis performed on the surface using energy dispersive spectroscopy revealed that the surface of TiZr alloy forms a top film including different oxides such as TiO2 and ZrO2, and for TiZrTa alloy, the surface has TiO2 + ZrO2 plus TaO2. Experiments demonstrated that Ta has the ability to increase the corrosion passivation of TiZr alloy.

Keywords

• ti-base alloys
• ta addition
• corrosion passivation
• electrochemical techniques
• surface morphology