Study of overall and local electrochemical responses of oxide films grown on CoCr alloy under biological environments

- High potentials in an oxide film on CoCr surfaces induce change in CPE distribution.
- CPE distribution of CoCr surfaces after applying high potentials agrees with 3D model.
- Oxide films grown on CoCr follow a closely Ohmic behaviour with graded thickness.
- Potentials at 0.7 Vvs Ag/AgCl cause nanostructural change in oxide surfaces.
- Nanopores of 10-50 nm diameter are formed along surface at 0.7 Vvs Ag/AgCl.

The interaction of the physiological medium and living tissues with the implant surfaces in biological environments is regulated by biopotentials that induce changes in the chemical composition, structure and thickness of the oxide film. In this work, oxide films grown on CoCr alloys at 0.5 V vs Ag/AgCl and 0.7 V vs Ag/AgCl have been characterized through overall and localized electrochemical techniques in a phosphate buffer solution and 0.3% hyaluronic acid. Nanopores of 10-50 nm diameter are homogeneously distributed along the surface in the oxide film formed at 0.7 V vs Ag/AgCl. The distribution of the Constant Phase Element studied by local electrochemical impedance spectroscopy showed a three-dimensional (3D) model on the oxide films grown at 0.5 V vs Ag/AgCl and 0.7 V vs Ag/AgCl. This behaviour is especially noticeable in oxide films grown at 0.7 V vs Ag/AgCl, probably due to surface inhomogeneities, and resistive properties generated by the potentiostatic growth of the oxide film.