In-Situ Monitoring of Molten Chloride Salt Chemistry and Corrosion Using Microelectrode

Molten chloride salts have emerged as promising candidates for coolant and energy storage medium applications. However, corrosion presents a significant challenge in their utilization, compounded by the complexities of material selection. This underscores the critical need for in-situ monitoring of molten chloride salt chemistry and corrosion. Such monitoring is essential for advancing nuclear reactor systems, optimizing reactor performance, and ensuring long-term stability. In this context, the integration of microelectrodes for in-situ monitoring of molten chloride salt chemistry and corrosion offers several advantages. Their small size and high spatial resolution enable precise characterization of electrochemical processes at microstructure specific sites at the corroding surfaces, facilitating a deeper understanding of corrosion mechanisms and redox reactions at the electrode-electrolyte interface. Additionally, microelectrodes provide faster response times and lower detection limits, enhancing sensitivity and enabling real-time monitoring of redox kinetics in molten salt systems. In this study, in-situ redox monitoring in high-temperature molten salts has been explored using microelectrode fabricated with glass-coated 25µm diameter Tungsten microwire. The diffusion coefficients of targeted ions, Eu 3+ or Ni 2+ , in 500°C LiCl-KCl eutectic molten salt has been addressed using cyclic voltammetry with varied scan rate. The electrochemical performance of the fabricated microelectrode has been validated by comparing the diffusion coefficient of the targeted species with those obtained using conventional macro-electrode. Furthermore, the potential applicability of the microelectrode as a high temperature scanning electrochemical microscopy (HT-SECM) for molten salt environment also has been addressed by performing approach curve experiment on Ni-Cr alloys. These results are promising and can be implemented to better understand both molten salt chemistry and grain-level corrosion under aggressive environment, ultimately ensuring the long-term stability of next-generation nuclear reactor system.