Corrosion resistance of titanium dioxide anodic coatings on Ti-6Al-4V

Abstract

The Ti–6Al–4V alloy is used for biomedical implants due to its corrosion resistance and biocompatibility, associated with the spontaneous formation of TiO2 oxide. However, the native film may be flawed and after some time of implantation in the body it may release metal ions. Oxides of higher thickness than naturally grown can be produced by anodic oxidation. The objective of this study was to evaluate the corrosion resistance of anodic TiO2 coatings, evaluating the influence of the thickness and crystalline structure of the coatings. Amorphous coatings were obtained from 27 to 140 nm that crystallized in anatase and rutile phases by heat treatment. The corrosion resistance was evaluated by potentiodynamic measurements in 0.9% sodium chloride, which is the main component of physiological solution. Evaluation of the electrochemical parameters showed that anodic coatings are more efficient barrier than the natural TiO2 oxide. As the oxidation processes influenced the electrochemical properties of metals by altering the resistance to corrosion, therefore they become important to study the electrochemical behavior of the oxides by electrochemical impedance spectroscopy.