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

Abstract

The potential and limits of the electrochemical noise (EN) measurement technique for the detection of stress corrosion cracking (SCC) initiation in austenitic stainless steels under simulated boiling water reactor (BWR) conditions was investigated at PSI within a small feasibility study. Because of the limited throwing power in low conductive, high purity water, it seems obvious that the distance between EN electrode and the specimen (or cracking location) plays an important role on the detectability of SCC initiation by the EN technique. This effect was evaluated by performing constant extension rate tensile tests in a simulated BWR environment (high purity water, T5288uC, p59 MPa, O 2 content52 ppm) with simultaneous potential noise measurements versus multiple reference electrodes. These experiments confirmed that for the detection of SCC initiation by EN measurements the electrode distance is a limiting factor for the application in low conductivity electrolytes. The detection sensitivity decreases with increasing distance between the specimen surface and the reference (or counter) electrode. Furthermore, it was evaluated that the basic/background noise level is very low in highly reducing environment.

Corrosion Monitoring Techniques in Subcritical and Supercritical Water Environments

“…In addition, the difficulty of applying EN in high-temperature water systems lies in how to reduce the internal noise of equipment to improve the accuracy and precision of data [84]. The key to successful monitoring is to use stable and reliable reference electrodes, ensure high conductivity of the test solution [114], and reduce the distance between the test electrode and the reference electrode to reduce background noise [115]. Figure 10 shows an example of EN monitoring results for Q235B steel exposed to the atmosphere of Tianjin city for 20 days [86].…”

Impact of Chloride on the Environmentally-Assisted Crack Initiation Behaviour of Low-Alloy Steel under Boiling Water Reactor Conditions

“…The EPN was measured via a Pt-wire (pseudo reference electrode) which was aligned around the V-notch of the specimen (Figure 4). This setup was developed, optimised, and verified during earlier research programmes [23,24].…”