Laser-texturing of stainless steel as a corrosion mitigation strategy for high-temperature molten salts applications under dynamic conditions

Abstract

Molten salts are utilized in a wide range of applications including nuclear, fuel cells, Carnot batteries, and Concentrated Solar Power (CSP). In order to enhance the profitability of next-generation CSP plants, increasing their efficiency is imperative. Ternary carbonate salts are capable of elevating the maximum CSP operating temperature, which results in improved power generation efficiency. However, higher temperatures lead to accelerated corrosion and more severe conditions for structural materials. In this study, nanosecond laser micromachining is investigated as a potential corrosion mitigation technique for molten carbonate salts in dynamic conditions. SS310 samples with laser-induced surface textures are subjected to the flow of molten Li2CO3–K2CO3–Na2CO3 at 600 °C for a period of 600 h. Laser treatment significantly impedes corrosion in SS310, as untreated samples display pitting and scaling, while minimal surface changes are noted on treated samples. Cross-sectional analysis of the samples reveals considerable peeling in the untreated samples and a 45% increase in the corrosion rate compared to the treated samples. The concentrations of Cr and Mg in the salt (determined through ICP analysis) are found to be twofold and fourfold higher than those in treated samples. Laser treatment renders Cr and Mg less accessible to the salt ions, particularly Li, which results in improved corrosion resistance.