Galvanic corrosion can occur as a macroscopic
and also as a microscopic process. Ni, Fe and Cr are the common
alloying constituents among which Cr is the primary constituent
that is most prone to dissolution. For alloys containing Ni, Fe and
Cr, Cr carbides are formed at the grain boundaries which become kinetically favorable paths for outward diffusion and dissolution of
Cr into molten fluorides due to the potential difference between
the matrix and Cr carbides.