Abstract
The degree of sensitization (DOS) of austenitic stainless steels and some nickel-based alloys (e.g., alloy 600) is evaluated by the electrochemical potentiokinetic reactivation (EPR) test. In this study a number of test solutions based on H2SO4 + KSCN composition have been evaluated to establish a reliable EPR test method for alloy 800. Different passivation (vertex) potentials are also tested. It has been shown that dilute test solutions with lower vertex potentials resulted in single loop (SL) and double loop (DL) EPR test methods that distinguished between different sensitized samples and also between sensitized and desensitized samples. It has been shown that an SL-EPR test in 1 M H2SO4 + 0.002 M KSCN (de-aerated) at 26 °C at a scan rate of 3 mV/s from a vertex potential of 700 mVSCE (180 s hold time) gave results that matched with the DOS indicated by microstructures and the Huey test results. Similarly, the DL-EPR test in 1 M H2SO4 + 0.002 M KSCN (de-aerated) at 26 °C, forward scanning from the OCP to + 700 mVSCE and then backward scanning from there to the OCP at a scan rate of 2 mV/s produced a good measure of DOS as indicated by the Huey test results. The effectiveness of the EPR test was ascertained by testing on alloy 800 containing Ti and Al (alloy 800 HT) and Nb (alloy 800 Nb).
Published Version
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