Electrochemical impedance spectroscopy study of Ti–6Al–4V alloy in artificial saliva with fluoride and/or bovine albumin

Objectives To investigate the electrochemical mechanism of Ti–6Al–4V alloy in acidic artificial saliva with NaF and/or bovine albumin (BA). Methods The electrochemical behavior of Ti–6Al–4V alloy was investigated using electrochemical impedance spectroscopy (EIS) measurements at the open circuit potentials. The electrolytes used included artificial saliva with 0–0.5% NaF, with 0.1% NaF+0.01–0.5% BA, and with 0.01–0.5% 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 (Rp) obtained from the EIS data. Surface chemical analyses were performed with X-ray photoelectron spectroscopy. Results The impedance was mainly characterized by the resistance and capacitance of a protective TiO2-based passive film on Ti–6Al–4V alloy when NaF concentration was low (≤0.01%). When NaF concentration was higher than 0.1%, the impedance was characterized by two capacitive and one inductive effects, which were related to the metalʹs charge transfer reaction and the decayed TiO2-based oxide film (capacitive effects), and the relaxation of the adsorbed Ti–F complex compound (inductive effect). The addition of 0.01–0.5% BA in 0.1% NaF-containing artificial saliva significantly increased the impedance of Ti–6Al–4V alloy compared to that without BA addition (p<0.001). The presence of BA in fluoride-free artificial saliva had no influence on the electrochemical impedance of Ti–6Al–4V alloy (p>0.05). Significance The EIS measurement technique is suitable for the study of the electrochemical behavior of dental alloy. The electrochemical mechanism of Ti–6Al–4V alloy in artificial saliva is related to the fluoride and bovine albumin concentration.