Electrochemical behaviour of titanium in H 2SO 4–MnSO 4 electrolytes

Abstract

The corrosion of titanium in H 2SO 4 electrolytes (0.001–1.0 M) at temperatures from ambient to 98 °C has been investigated using steady-state polarization measurements. Four distinct regions of behaviour were identified, namely active corrosion, the active–passive transition, passive region and the dielectric breakdown region. The active corrosion and active–passive transition were characterized by anodic peak current ( i m) and voltage ( E m), which in turn were found to vary with the experimental conditions, i.e., d ( log ⁡ ( i m ) ) / dpH = − 0.8 ± 0.1 and d E m/d pH which was −71 mV at 98 °C, −58 mV at 80 °C and −28 mV at 60 °C. The activation energy for titanium corrosion, determined from temperature studies, was found to be 67.7 kJ mol −1 in 0.1 M H 2SO 4 and 56.7 kJ mol −1 in 1.0 M H 2SO 4. The dielectric breakdown voltage ( E d) of the passive TiO 2 film was found to vary depending on how much TiO 2 was present. The inclusion of Mn 2+ into the H 2SO 4 electrolyte, as is done during the commercial electrodeposition of manganese dioxide, resulted in a decrease in titanium corrosion current, possibly due to Mn 2+ adsorption limiting electrolyte access to the substrate.