Corrosion of titanium alloys in pressurized water at 300 °C and 15 MPa

Abstract

Commercially pure titanium (Ti CP) and two titanium alloys (Ti 64 and Ti10-2-3) representative of different metallurgical classes were exposed to pressurized water at 300 °C, 15 MPa in a dedicated stainless steel corrosion loop up to 1632 h. Mass uptake measurements as well as extensive characterization of the oxides formed on the polished samples using scanning and transmission electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, photoelectrochemistry and glow discharge optical emission spectroscopy led to the following main conclusions: • The oxide scale was made of a thin and continuous TiO2 layer topped by small TiO2 anatase crystallites and large FeTiO3 ilmenite crystallites. • The interface tortuosity increased with exposure duration, as well as the amount of crystallites. From 217 h exposure, the thickness of the thin continuous TiO2 layer remained constant with exposure duration. • The mass uptake increased approximately linearly with exposure duration. These observations were consistent with a corrosion mechanism involving simultaneous oxide growth, dissolution and precipitation. The corrosion rate of the three studied materials was estimated to be around 3 µm/year.