Electrochemical Study of TA2 Titanium in a High-Temperature and -Pressure Water Environment

The corrosion behaviors of TA2 titanium were investigated by in situ electrochemical measurements in a solution of 2.3 ppm Li+ and 1500 ppm B3+ at a temperature of up to 300 °C. The morphology, phase structure, and composition of the oxide film, after 800 h exposure time in a solution at 300 °C and 14 MPa, were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), etc. The growth mechanism of the oxide film based on the activation energy was discussed. The potentiodynamic polarization and electrochemical impedance spectroscopy analyses showed that the corrosion resistance of titanium significantly weakened when increasing the solution temperature from 30 to 300 °C, but it increased in the initial stage of holding time (0–66 h) at 300 °C, then gradually decreased (66–378 h), and reached a stable state after 378 h. The oxide film, which was about 5 μm thick, consisted of anatase phase and a small amount of B2O3. The growth mechanism is a combination of layer by layer and island growth.