Numerous studies1 have been conducted on the effect of anodic or cathodic polarization on time to failure as a tool to differentiate active path corrosion (APC) from hydrogen embrittlement (HE).
Recently, Wilde2 pointed out, however, the potential dependence of time to failure cannot be an absolute criterion to distinguish between the two mechanisms. He conducted a hydrogen permiation study as well as a crack propagation study under anodically or cathodically polarized conditions on high strength martensitic stainless steel. He suggested that the cracking mechanism was HE, regardless of the applied potentials.
By acoustic emission technique, it is possible to detect high amplitude acoustic signals accompanying hydrogen induced microcracking at the advancing crack tip,3,4 in contrast to APC where cracks propagate by anodic dissolution along with preferential paths and significant acoustic emission cannot be expected.
The purpose of this study is to differentiate the two mechanisms (APC and...
