Electrochemical behavior of titanium in artificial saliva: influence of pH

Titanium is the most common material chosen for dental implants because it is highly corrosion resistant because it constantly reforms a protective passive film layer. The formation and composition of the passive film layer is dependent on the environmental conditions. If the stable oxide layer is damaged, the titanium surface underneath can corrode. The purpose of this study was to determine if basic corrosion of commercially pure titanium (CpTi) alloy in artificial saliva was affected by pH and to understand the corrosion kinetics/mechanisms of CpTi as a function of pH. In this study, titanium alloy discs were subjected to corrosion tests. Before the tests, all samples were cleaned and polished using standard metallographic preparation methods. Artificial saliva was used as the testing medium. The following pH values were tested: 3.0, 4.5, 6.0, 6.5, 7.5, and 9.0. Different pH values were achieved by adding lactic acid (acidic) or NaOH (basic) in appropriate amounts. Potentiodynamic curves indicated behavior change at each pH. In addition, the corrosion current density value determined from the potentiodynamic curve exhibited the poorest corrosion resistance for pH 7.5. The Nyquist plot (from the electrochemical impedance spectroscopy results) indicated that pH 7.5 had the poorest resistance. Scanning electron microscopy images indicated that pH levels of 6.5, 7.5, and 9.0 had considerable surface corrosion. The results showed that the media's pH significantly influenced the corrosion behavior of CpTi. The poor corrosion behavior at the neutral pHs invites some concerns and highlights the need for further study.