Outcome of work at National Building and Civil Engineering Institute (ZAG), Slovenia [Inspection and measurement]

Testing was undertaken on type 321 stainless steel in aqueous conditions under two regimes: - At atmospheric pressure at elevated temperature (up to 70°C) in 0.5M NaCl + 0.5M H₂SO₄ (pH 2); - At 100 bars in 300°C water with 1000 ppm B, 2 ppm Li (pressurized water reactor (PWR) conditions). Atmospheric test specimens were subjected to a static load near the yield point to initiate SCC, whilst at PWR conditions slow strain rate tests were used. Monitoring was undertaken using electrochemical noise (EN), acoustic emission (AE) technique, measurement of tensile test sample elongation and simultaneous digital imaging of the surface by charge coupled device camera. The main aim of the research was to identify a reliable technique for monitoring of CISCC processes by showing a correlation between different measurement techniques and microstructural evidence of corrosion processes. Although the testing was undertaken in aggressive, aqueous conditions, the focus was on the evaluation of AE as a detection technique, which is deployable in non-aqueous contexts and therefore the work contributes towards the provision of reliable techniques for the detection of CISCC.