Electrochemical Behavior of Ti-6Al-4V in Saliva with Fluoride and/or Albumin

Objectives: This study was to investigate the electrochemical behavior of Ti-6Al-4V alloy in artificial saliva with NaF and/or bovine albumin (BA) using electrochemical impedance spectroscopy (EIS) measurement and surface chemical analysis. Methods: The EIS measurements were carried out at the open circuit potentials of Ti-6Al-4V alloy in the test electrolytes with a sinusoidal potential of 10 mV. The electrolytes chosen in this study included the artificial saliva with 0~0.5% NaF, with 0.1% NaF + 0~0.5% BA, and with 0~0.5% BA at pH 5 and 37 °C. One-way ANOVA was used to analyze the influence of NaF and BA concentration on the polarization resistance (R_p) obtained from the EIS data. Surface chemical analyses were performed with electron spectroscopy for chemical analysis (ESCA). Results: The impedance was mainly characterized by the resistance and capacitance of TiO₂ passive film on Ti-6Al-4V alloy when NaF concentration was low (£0.01%). While when NaF concentration was higher than 0.1 %, the impedance was characterized by two capacitive and one inductive effects, which were related to the R-C (resistance-capacitance) circuits for metal¢s charge transfer reaction and the decayed TiO₂ film (capacitive effects), and the relaxation of the adsorbed Ti-F complex compound (inductive effect). The R_p value of Ti-6Al-4V alloy in artificial saliva decreased with increasing the NaF concentration (p<0.001). The presence of BA, regardless of the concentration, in 0.1% NaF-containing artificial saliva increased the R_p value of Ti-6Al-4V alloy compared to that without BA addition (p<0.001). The addition of BA in artificial saliva had no influence on the electrochemical behavior of Ti-6Al-4V alloy (p>0.05). Conclusions: The NaF concentration in artificial saliva and the BA concentration in 0.1% NaF-containing artificial saliva, respectively, have statistically significant influence on the electrochemical behavior of Ti-6Al-4V alloy (p<0.001); while the BA concentration in fluoride-free artificial saliva shows no significant influence (p>0.05).