Container Material Influence on Corrosion

    Molten salts are ionic fluids that can sustain electrical currents and electrochemical corrosion mechanisms that depend on electron transfer. The design considerations for molten salt coolant systems usually dictate the use of several different materials, which may have differing electromotive potentials (galvanic potentials). Unfortunately, galvanic potential rankings have not been developed for molten salts. The corrosion rate of a chromium-containing alloy can be accelerated considerably by a galvanic couple; corrosion rates can be increased more than 30 times by switching from an inert crucible to one comprised of a more reactive metal, such as iron (Ozeryanaya, 1985). The process has been observed in corrosion of Incoloy 800H in FLiNaK, in which the corrosion rate was significantly greater for a graphite crucible compared to an Incoloy 800H crucible (Olson, 2009; Sridharan, 2009).

    A graphite test cell was built at UW for initial alloy screening with FLiNaK salt, and different FLiNaK purification methods, to compare FLiNaK against KCl-MgCl2 and to test several coatings. The final molten salt exposure capsule design is shown.