EuCl3-mediated corrosion of Ni and Ni-20Cr model alloy in LiCl-KCl molten salt

Corrosion of structural materials is a key engineering challenge for the development of molten salt reactors (MSRs). Metal ion impurities in the salt, which are inevitable due to their natural evolution in a reactor (e.g., fission products and corrosion products) can significantly impact the corrosion performance of structural materials. In this work, we investigated the effects of one fission product, Eu in its 3+ oxidation state, on the corrosion behaviors of pure Ni metal and Ni-20Cr model alloy in molten LiCl-KCl eutectic using in situ optical spectroscopy, post-corrosion inductively coupled plasma mass spectrometry (ICP-MS), and electron microscopy-based techniques. The EuCl 3 -containing salt was found to be extremely corrosive to both Ni and Ni-20Cr. Detailed microstructural characterization revealed that pure Ni primarily exhibited planar corrosion fronts with occasional shallow intergranular attacks, while Ni-20Cr alloy showed severe localized intergranular attacks with selective Cr leaching and salt penetration near grain boundaries. Additionally, this study uncovered the unique intragranular crystallographic attack of Ni-20Cr following exposure to EuCl 3 -containing salt. Overall, these findings are crucial for understanding how oxidizing salt impurities such as EuCl 3 affect corrosion reactions and diffusion kinetics at the salt-material interface, thereby influencing corrosion microstructure evolution pathways.