Abstract
The electrolytic reduction of a spent oxide fuel involves the liberation of oxygen in a molten salt LiCl–Li2O electrolyte, which creates a corrosive environment for typical structural materials. In this study, the corrosion behaviors of Al–Y-coated specimens in a Li molten salt kept under an oxidizing atmosphere at 650 °C for 72 and 168 h were investigated. The weight loss fraction of the coated specimen to bare specimen was approximately 60% for 3% Li2O and 54% for 8% Li2O at 72 h, and approximately 38% for 3% Li2O and 30% for 8% Li2O at 168 h. Corrosion was induced in the LiCl–Li2O molten salt by the basic oxide ion O2− via the basic flux mechanism, and the corrosion product was found to be dependent on the activity of the O2− ion. The increase in weight loss may have been caused by the increase in the O2− concentration due to the increase in the Li2O concentration rather than being because of the increased reaction time. The Al–Y coating was found to be beneficial for hot corrosion resistance, which can be useful for handling high-temperature lithium molten salt under an oxidizing atmosphere.
Highlights
Molten salts are used in various industries due to their high electrical conductivity, high-density processing, and fluid properties
Through the basic fluxing mechanism, in a molten salt with a high concentration of O2−, O2− reacts with the oxide formed at the beginning of oxidation, and the oxide is dissolved in the molten salt and reprecipitates as crystal grains of the oxide on the alloy surface [49]
Considering that the oxide ion O2− in the basic fluxing mechanism significantly participated in the corrosion reaction in the high-temperature molten salt, the increase in weight loss may have resulted from the increase in the oxide ion O2− concentration due to the increased Li2O concentration, rather than the effect of the coating
Summary
Molten salts are used in various industries due to their high electrical conductivity, high-density processing, and fluid properties They have been attracting increasing attention for applications in jet engines [1,2,3,4,5], fuel cells [6,7,8], energy storage [9,10,11], and metal purifications [12,13,14]. In the absence of an Al source in the electrolyte or alloy, the possible applications of generalpurpose commercial alloys, for example, in high-temperature molten carbonate fuel cells (MCFCs), waste incineration systems, and molten salt electrolysis systems, can be greatly expanded if similar corrosion resistance is achieved by supplying Al through the surface treatment of the structural material
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