Electrochemical Corrosion Behavior of Ti35 Alloy in Nitric Acid Containing Fluoride Ions

The open circuit potential (OCP), potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) of Ti35 alloy were tested by an electrochemical test system in 6 mol/L nitric acid solution containing fluoride ions and the effect of the fluoride ion on the corrosion resistance of Ti35 alloy was investigated. The results show that the corrosion resistance of the alloy decreases with the increase of fluoride concentration while the alloy still exhibits good corrosion resistance in general. The critical concentration of fluoride ions affecting the corrosion resistance of the alloy is about 1.25 mmol/L. Furthermore, the mixed potential theory was adopted to explain the undermined mechanism of the changing corrosion resistance of the alloy.