The effect of surface and heat treatments on corrosion of unalloyed titanium implants

Unalloyed titanium (Ti) implants are being increasingly used in the orthopedic and dental fields. The American Society for Testing and Materials recommends that metallic implants be cleaned, passivated, and sterilized prior to implantation. Heat treatments are often used to sterilize implants and sometimes to stabilize osteoconductive coatings, if any. This study examined the effect of passivation and temperature-of-heat-treatment on the corrosion of unalloyed titanium implants. After acid cleaning, specimens were heat treated in air at 205°C (205C) for 3 h or passivated in nitric acid and then heat treated in air at 205°C for 3 h, 427°C for 1h (427CP), 516°C for 1h (516CP), respectively. Potentiodynamic DC analysis was conducted at room temperature in oxygenated 0.9% sodium chloride (buffered pH 7.4) solution. Sufficient replicates were examined to provide a confidence level of at least 95% (n⩾5). Although there were no statistical differences among the equilibrium corrosion current densities, 516CP had the lowest equilibrium corrosion potential (Ecorr). Thus, passivation did not alter corrosion characteristics while specimens heat treated at 516°C were the most likely to corrode in a 0.9% saline environment, as indicated by the Ecorr