Mitigation of Impurity Driven Corrosion in Molten Chloride Salt Cooling Loops - A Review

Abstract

Molten chloride salt mixtures have found renewed focus in use as secondary and primary loop heat transfer fluids for energy generation and storage systems, one main challenge that hinders their use is impurity driven corrosion. The corrosive nature of the molten chloride salt mixtures has been studied extensively; the results show that significant surface dealloying occurs. This paper reviews the damage caused by chloride molten salt mixtures and its control, either by pre-oxidation of the alloy or thermal and/or chemical purification processes. Alumina and silica forming alloys provide protection against corrosion, but chromia forming alloys are prone to corrosion primarily by Cr dealloying. Both chemical and thermal purification are effective methods removing H₂O (a key problematic impurity) OH^-, HCl, which decreases hydrolysis 2 reactions, and reduces corrosion. Further research needs to be conducted on the protectiveness of pre-oxidized silica forming alloys and corrosion reduction via chemical purification methods on non-Mg containing salt mixtures.