Electrochemical Corrosion Investigation of Structural Materials in Molten Fluoride Eutectic Salts

Abstract

This thesis investigates the corrosion behavior of structural materials when exposed to molten fluoride eutectic salts using electrochemical techniques. The research objective is to rank and screen metal structural materials for nuclear reactors based on their performance in determining physical properties, including impedance, corrosion rates, and polarization in FLiNaK salt at 700 °C. The ranking and screening process involved evaluating the materials' performance in these tests and establishing a relative hierarchy. Criteria such as lower corrosion rates, higher impedance values, and increased polarization resistance to corrosion were considered during the analysis. Electrochemical impedance spectroscopy (EIS), Tafel, and polarization resistance (Rp) measurements were conducted for nickel, stainless steel 304, stainless steel 308, Inconel 600, Inconel 617, and HastelloyN. The results revealed variations in the physical properties and corrosion mechanisms of the alloys based on their composition. The EIS analysis provided insights into the corrosion mechanisms and interface properties of the materials, contributing to the development of improved materials in future work. Additionally, the Rp measurement indicated the materials' resistance to corrosion. The findings of this study have significant implications for the design and selection of materials for future high-temperature applications involving molten fluoride eutectic salts, including Gen-IV nuclear reactors and molten salt batteries. The knowledge gained from this research contributes to the development of more durable and efficient materials by delivering important physical property data of metals in molten salts at high temperatures. This knowledge can facilitate the use of these materials as structural components capable of withstanding harsh environments, ultimately enhancing the reliability and safety of high-temperature systems up to 700 °C.masters, M.S., Chemical & Biological Engineering -- University of Idaho - College of Graduate Studies, 2023-0