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 (E_corr), corrosion current density (i_corr) and polarization resistance (R _p). 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 1-2μAcm^-2 at 37°C. In contrast, the corrosion current densities in biological fluids were lower at an order of 0.1-0.3μAcm ^-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.