A study of the electrochemical reactivity of titanium under cathodic polarization by means of combined feedback and redox competition modes of scanning electrochemical microscopy

The effect of cathodic polarization on the electrochemical behavior of the thin titanium dioxide film formed by anodic pretreatment over pure commercial titanium metal for biomaterial application was investigated in situ using scanning electrochemical microscopy (SECM). Quantitative information on the electron transfer rates (k(eff)) at the titanium surface was obtained using the feedback operation of SECM with ferrocene-methanol (FcMeOH) as electrochemical mediator. An increase of k(eff) values with the increase of the negative polarization was detected, a feature that correlates well with the decrease of titanium oxide resistance with increasing cathodic polarization observed using electrochemical impedance spectroscopy (EIS). In addition, SECM operation in the redox competition mode proved that hydrogen was absorbed in the surface oxide film leading to changes in conductivity and electrochemical reactivity.