Investigation on the corrosion behavior of Ti–6Al–4V implant alloy by electrochemical techniques

The electrochemical corrosion behaviors of Ti–6Al–4V implant alloy were studied in three biological fluid solutions, i.e. urine, serum and joint fluid. For comparison, the corrosion characteristics of Ti–6Al–4V implant alloys were also investigated in phosphate buffered saline (PBS) solutions at different pH values and temperatures. The electrochemical corrosion properties of Ti–6Al–4V alloys were investigated by electrochemical techniques, such as cyclic voltammetry, potentiodynamic method, and ac impedance spectroscopy. The corrosion resistance of Ti–6Al–4V implant alloys in different biological solutions was evaluated in terms of corrosion potential (Ecorr), corrosion current density (icorr) and polarization resistance (Rp). The corrosion kinetic parameters were calculated from both the Tafel extrapolation analysis and ac impedance analysis. It was observed that the corrosion current densities of Ti–6Al–4V implant alloy in PBS solutions of different pH values were about the same order of magnitude, which was at a level of 1–2 μA cm−2 at 37 °C. In contrast, the corrosion current densities in biological fluids were lower at an order of 0.1–0.3 μA cm−2 at 37 °C. The ac circuit elements for corrosion interface of Ti–6Al–4V alloy in various solutions were reported based on the Randle equivalent circuit model. It was found that the Ti–6Al–4V implant alloy in three biological body fluid solutions showed a characteristic of one capacitive behavior. The experimental results obtained from different electrochemical techniques were compared and discussed.