塩酸を含むメタノール溶液中におけるTiの環境脆化

抄録

Environment-assisted Cracking (EAC) of Ti in methanol solutions containing various concentrations of HCl has been investigated by using a slow strain rate testing apparatus with a dynamic observation system. In the EAC test, dissolved oxygen and water content were strictly controlled because it is known that these two factors influence the cracking of this system. It was observed that cracks initiated from black pits which were generated during the test, and that the cracking mode was intergranular and transgranular at the initial and the final stage of the crack propagation, respectively. Cracking occurred at 0.004 to 0.04 and 0.0004 to 0.04 kmol·m⁻³ HCl for initial strain rates of 8.3×10⁻⁷ and 2.5×10⁻⁶ s⁻¹, respectively. This behavior was also influenced by electrode potential, that is, the cracking occurred above a critical potential depending on the concentration of HCl. The critical potential was expressed as a negative function of a logarithm of the concentration of HCl, and the potential was lowered as the initial strain rate increased. It was concluded that initiation of EAC for this system is mainly controlled by an anodic localized corrosion mechanism.