Detection of SCC initiation in austenitic stainless steel by electrochemical noise measurements

Abstract

The electrochemical noise (EN) measurement technique is one of the most promising tools for continuous in situ corrosion monitoring in technical systems with a certain potential to be used for the detection of stress corrosion cracking (SCC). To evaluate the suitability of the EN technique for the detection of SCC initiation, a small but systematic test programme was started, performing EN measurements on type 304 austenitic stainless steel during constant extension rate tensile tests in aqueous thiosulphate solution at room temperature. SCC could be detected by EN measurements, which was verified by interruptions of the experiments at different stages, by testing steel with different degrees of sensitisation and by post-test fractography in the scanning electron microscope. Conclusions on the cracking mechanism could be drawn based on the current noise signal pattern.

Influence of reference electrode distance and hydrogen content on electrochemical potential noise during SCC in high purity, high temperature water

“…EN transients and an increase in the electrochemical current (ECN) and decrease in the electrochemical potential noise (EPN) signal level, indicating SCC initiation, could be observed during the room temperature experiments. 4 CERT tests with round bar tensile specimens in high temperature water showed a similar behaviour, although single transients could not be identified in most cases. These results together with tests combining the EN measurement technique with independent online crack growth monitoring by direct current potential drop technique revealed that early SCC detection by EN is possible under stable and stationary lab conditions in oxygenated high temperature water.…”

“…The electrochemical noise (EN) measurement technique is a promising tool for continuous, in situ corrosion monitoring in technical systems and has the potential to detect nucleation and initiation of localised corrosion processes. 4 Currently, EN seems to be the major promising technique with some potential for the early detection of SCC initiation in structural components of BWRs and PWRs, although no extensive systematic studies have been performed so far and the basic and quantitative understanding of EN during SCC is still rather limited. [5][6][7][8][9][10][11]…”

Corrosion monitoring techniques for detection of crack initiation under simulated light water reactor conditions

“…see Refs. [15][16][17][18][19][20][21][22][23][24][25][26][27]. In some cases, the reliability of the EN measurements to detect EAC has been proven by simultaneous measurements of elongation, load or AE, 19,21,25,26 where current transients could be clearly correlated with sudden changes in elongation, load drops or AE events, indicating crack initiation.…”

Evaluation of multiple stress corrosion crack interactions by in-situ Digital Image Correlation

“…Between the several applications of EN, the possibility and sensitivity to detect the initiation process of cracking must be cited. Several investigators have already reported the relation between crack initiation and EN measurements in different systems [45,46]. Their results were discussed on the base of the slip dissolution model and the film-rupture model.…”