(385c) Electrochemical Corrosion Measurements in Molten Flinak Salt

Molten fluoride salts have attracted interest as fuel and/or coolant for several different molten salt reactor (MSR) designs. Fluoride salts have many advantageous properties for these applications, such as high ionic conductivity, good heat transfer capacity, radiation insensitivity and high solubility for actinides. However, the corrosion of storage materials owing to impurities in the molten salt has not been thoroughly studied, especially in fluoride salts. Some researchers have studied corrosion in fluoride salts, but they only compared the morphologies and the elemental composition of the metal’s surface or near surface region after static corrosion tests. LiF-BeF₂ (FLiBe) and LiF-NaF-KF (FLiNaK) are candidate fluoride salts for these applications. In this study, we used two electrochemical methods for measuring corrosion rate in FLiNaK: linear polarization and zero resistance ammeter (ZRA). ZRA is the most suitable technique for monitoring corrosion processes in situ, since it yields real time data that can be directly related to corrosion without applied potential. ZRA data will be presented and compared to morphologies and element mapping of the surface of the metal alloys obtained by using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In addition, the composition of the salts was analyzed by inductively coupled plasma – mass spectroscopy (ICP-MS) before and after ZRA measurements to determine which corrosion products are soluble in the molten fluoride salt.