Electrochemical Dealloying of Binary Ni-Cr Alloys in Molten FLiNaK Salts

In molten fluoride salt system, the preferential leaching of chromium or dealloying through grain boundary migration is a prevalent phenomenon that has been observed in many materials system. Dealloying was primarily discussed in the context of microstructural attributes; however, the role of electrochemical processes at the alloy-salt interface was often ignored. For instances, the partitioning of alloying elements, corrosion regime, surface and bulk diffusion kinetics are all dependent upon electrochemical potential and the resulting corrosion morphology. In this work, electrochemical dealloying of binary Ni-Cr alloys (Ni5Cr, Ni10Cr, Ni15Cr, Ni20Cr) was studied in molten LiF-NaF-KF eutectic salt at 600°C. A series of electrochemical methods, including linear sweep voltammetry and potentiostatic hold, were performed on these materials in FLiNaK salts with and without the additions of NiF₂ and CrF₃ salts. The particular aim is to identify the parting limit and the critical potential for dealloying of Ni-Cr alloys in FLiNaK salts. The results can not only be foundational to the prediction of alloy corrosion morphology in molten fluorides, but also the fabrication of hierarchical porosity which may exhibit potential engineering applications.