Electrochemical noise generated during the stress corrosion cracking of sensitized alloy 690

摘要

Electrochemical noise in current has been used to monitor the stress corrosion cracking (SCC) susceptibility of alloy 690 sensitized at 700 ℃ during 48 h in sodium thiosulfate at 90 ℃. At 48 h of aging, the specimen failed by SCC and the corrosion current pulses had high intensity and low frequency, and were associated with the nucleation and propagation of stress corrosion cracks during slow strain rate tests. When the alloy was immune to SCC, the observed corrosion current pulses had a much higher frequency and lower intensity, indicating either uniform corrosion or passivation. The type of transients observed do not indicate the mechanism responsible for the observed embrittlement, but only the cracking initiation or propagation process.