Electrochemical impedance spectroscopic studies of titanium and its alloys in saline medium

The influence of potential on electrochemical behaviour of pure Ti, Ti-6Al-7Nb, and Ti-6Al-4V ELI alloy under saline conditions were investigated by electrochemical impedance spectroscopy (EIS). All measurements were carried out in saline solution (0.9% NaCl) at different impressed potentials (corrosion potential (E-corr), 0 mV (SCE) and + 500 mV (SCE)) for 1 h. The experimental results were compared with those obtained by potentiodynamic polarization curves. The corrosion current densities obtained for the titanium alloys showed lower values than for pure Ti, indicating the formation of a stable passive film with time. Electrochemical impedance spectroscopic studies indicated that the resistance of the passive film increased with the impressed potential. The impedance spectra were fitted using a non-linear least square (NLLS) fitting procedure. The magnitude of the corrosion resistance of titanium alloys under saline solution was compared and results are presented.