Stress corrosion cracking and potential dependence of SUS 304 steel single crystals in MgCl2 solutions.

The susceptibility to stress corrosion cracking (SCC) and its potential dependence were examined for SUS 304 steel single crystals with the single slip orientation, i.e., 0.50 in Schmid factor.The SCC tests were carried out in boiling 25-45% MgCl2 solutions under various constant potentials in the present study.The corrosion morphology of the specimen surface SCC-tested was dependent on both MgCl2 concentration and applied potential: The potential range for SCC occurrence of which critical potential was -380--400mV (SCE) increased with increasing MgCl2 concentration. In this case, the threshold concentration for cracking was about 30%, below which the potential range for pitting appeared. The uneven general corrosion occured as the potential was shifted to more noble values. On the other hand, the cracks mentioned above initiated from the specimen surface which was easy to induce slip-steps by plastic deformation. The fracture surface characterized by river-like pattern was formed by the crack growth along ‹110› direction on {110} plane.