Electrochemical noise characteristics of IGSCC in stainless steels in pressurized high-temperature water

Transient behavior of short-circuit current of Type 316 stainless steels (UNS S31600) during a slow strain rate tensile (SSRT) test in high-purity oxygenated water at 288°C was investigated and their correlation with stress corrosion cracking (SCC) was discussed. Short-circuit current at free corrosion potential between a specimen under slow-rate straining and a counter electrode which was made of the identical alloy to the specimen was continuously monitored using a zero-resistance-ammeter. Spike-like current transients were observed after yielding. The current pulses had short rise time, typically a few seconds, and slow decay behavior, 100-1000 seconds; This characteristic was considered to correspond to the slip dissolution processes. Although the current transients were observed both on the solution treated material and on the sensitized one, characteristics of the current transients reflected well the difference in SCC susceptibility between the materials. Current transients from the sensitized material had higher peak intensity and slower decay rate than those from the solution treated one. Capability of the current noise monitoring for detecting SCC initiation in austenitic stainless steels in high-temperature high-pressure water was demonstrated and it was suggested that the current noise can provide real-time evaluation of SCC behavior.