純チタンのCH₃OH/HCl溶液中における応力腐食割れとその電位依存性

抄録

The susceptibility to stress corrosion cracking (SCC) and its potential dependence of pure titanium were investigated under the constant-loading condition. The SCC tests were conducted in CH₃OH solutions containing HCl under given potentials at room temperature.
The critical potential for SCC in CH₃OH/0.4%HCl solution moved to the negative direction, and the susceptibility to SCC increased. The potential range for SCC corresponded with the active region in the potentiostatic anodic polarization diagram, and the test specimens were attacked by uneven general corrosion when the potential was moved to the positive direction. The fracture mode was also dependent on the above-mentioned potential range: The transition of intergranular to transgranular fracture was observed in the potential range of SCC whereas only intergranular fracture was found in that of general corrosion. The addition of Pt which impeded hydrogen absorption by promoting hydrogen evolution decreased the susceptibility to SCC.
From the evidences introduced here, it is concluded that the intergranular and subsequent transgranular fracture are caused by the mechanical stress associated with the absorption of hydrogen generated by the dissolution reaction.