  The interface between NiCr alloys and FLiNaK molten salt exhibits complex
corrosion behavior, mainly driven by intricate chemical interactions involving
Cr and F$\mathrm{^-}$ ions. Understanding these dynamic reactions is crucial
for developing effective corrosion mitigation strategies to ensure the
long-term durability of Ni-based alloy components in molten salt technologies.
However, obtaining molecular-level understanding through experiments is
challenging. To address this, we utilize reactive molecular dynamics
simulations enabled by a reactive force field, ReaxFF, to investigate detailed
reaction dynamics at the atomic level. Since there is currently no available
force field involving fluoride salt and Ni-based alloys, we first present the
development of the ReaxFF parameter set for Ni/Cr/F/Li/Na/K based on extensive
first-principles calculations. With this force field, we achieve a strong
agreement for the structure of FLiNaK molten salt by comparing the pair
distribution functions with experimental and simulation results. Furthermore,
it successfully reproduces the experimental phenomenon of Cr dissolution in
fluoride salt, with the corrosion rate depending on the alloy and salt
compositions. Particularly, it reveals that increasing the concentration of Li
can enhance the formation of a compact double layer, mitigating Cr dissolution.
This work enables a fundamental understanding of the interfacial behavior
between fluoride salt and NiCr alloys.
