Effect of immersion time on the passive and electrochemical response of annealed and nano-grained commercial pure titanium in Ringer's physiological solution at 37°C.

In the present study, various electrochemical tests were used to investigate the passive and electrochemical response of annealed and nano-grained commercial pure Titanium in Ringer's physiological solution at 37°C. Nano-grained pure Titanium, which typically has an average grain size of 90±5nm, was obtained by six-cycle accumulative roll bonding process. Polarization and electrochemical impedance spectroscopy plots illustrated that as a result of grain refinement process, the passive response of the nano-grained sample was improved compared to that of its coarse-grained counterpart in Ringer's physiological solution. Mott-Schottky analysis indicated that the passive films behaved as n-type semiconductors in Ringer's physiological solution and grain refinement did not change the conductivity type of the passive films. Additionally, Mott-Schottky analysis showed that the donor density decreased by grain size reduction. Finally, nano-grained sample appeared to be more suitable for implant applications, mainly due to the formation of thicker and less defective oxide film.