In Situ Monitoring Techniques and Analysis Theory for Electrochemical Corrosion in Subcritical and Supercritical Aqueous Systems

Subcritical and supercritical water systems, critical in nuclear energy, thermal power, and pollutant treatment, operate under extreme conditions that intensify material corrosion. In-situ electrochemical monitoring provides essential real-time data for optimizing operational conditions and enhancing corrosion prediction models. This paper evaluates high-temperature electrochemical monitoring techniques, focusing on the performance of reference electrodes and research platforms. While hydrogen electrodes offer precision, their operational complexity limits practicality. Metal/metal oxide electrodes provide robustness but suffer from potential instability, and yttria-stabilized zirconia electrodes, though suitable for high temperatures, are fragile and challenging to fabricate. External pressure-balanced reference electrodes and flow-through versions represent promising alternatives but require further refinement, particularly in thermal liquid junction potential calibration. The development of advanced research platforms, facilitating in situ electrochemical testing via techniques like electrochemical impedance spectroscopy and potentiodynamic polarization curves, is also discussed. The point defect model and its supercritical water adaptation provide a robust framework for understanding corrosion mechanisms at the microstructural level. Ongoing innovation in electrode design, platform scalability, and diagnostic techniques will be essential to advancing corrosion monitoring in extreme environments, ensuring enhanced material performance and operational safety.