We investigated the mechanism of stress corrosion cracking during the so called "induction period" before cracks initiated, by using the method of preimmersion.
During the induction period, the corrosion potential of test piece rose more and more independently of the load value, until at last it reached the necessary value causing the occurrence of "micro-pitting" which was believed to be the initial stage of stress corrosion cracking. If the necessary value of stress was applied at that time, cracks immediately started.
Then it may be said that the stress is not necessary untill the potential of specimen reaches the necessary value described above.
The material was not found to be attacked by corrosion agent, and become brittle during the induction period.
Moreover, we obtained the values of the threshold stress for crack initiation and that for crack propagation, and generally speaking the latter had a lower value than the former.