Laser-induced carbonization of stainless steel as a corrosion mitigation strategy for high-temperature molten salts applications

Abstract

New heat transfer fluids are necessary to shift the operation temperature of concentrating solar power plants (CSP) to higher temperatures. Ternary carbonate salts (Li2CO3-K2CO3-Na2CO3) are a promising candidate. However, higher temperature translates to harsher operating conditions for CSP structural components as corrosion is more prevalent. In this work, we explore, for the first time, the use of laser micro-machining technology as a surface modification method to inhibit corrosion of CSP structural materials by molten salts. The corrosion behaviour of SS310 in molten ternary carbonate salt is investigated through static immersion for 600 h. Nanosecond laser treatment results in the adhesion of organic groups in the form of hydrocarbons. These then decompose into carbon and contribute to corrosion inhibition through carbonization and the formation of carbide layers. This is confirmed by the reduced diffusion of Li + ions in the SS310, the formation of denser corrosion products and the protection of chromium oxide layers.