Electrochemical behaviors of tantalum in anhydrous ethanol containing hydrogen sulfate ions

The electrochemical behaviors of Ta in tetrabutylammonium hydrogen sulfate (TBAHS) ethanol solutions were studied using potentiodynamic polarization, cyclic voltammetry, potentiostatic current time transient and impedance techniques. The results revealed that no active-passive transition is presented in the cyclic voltammogram, and the anodic current density increases with the increase of solution temperature, TBAHS concentration, potential scan rate and water content. The apparent activation energy is about 43.389 kJ/mol and the dissolution process is diffusion-controlled. Potentiostatic measurements showed that the current density gradually decays to a steady value when the potential is low; however, when the potential is higher than a certain value, the current density initially declines to a minimum value and then increases gradually. The resistance of passive film decreases with increasing potential, and inductive loops are presented when the potential is higher than 2.0 V.