Protective Laser Cladding Coatings for Thermal Energy Storage Tanks in contact with Molten Salt-Based Nanofluids

Abstract

Intermittency of renewable energy sources is a critical problem. Concentrated Solar Power (CSP) power plants with thermal storage systems offer one of the main solutions. Among the many storage processes, nanofluids are a method of improving thermal performance but inducing corrosion of storage units. This study investigates the potential of Inconel-625 and Stellite-6 coatings deposited by laser cladding in preventing nanofluid-induced corrosion in CSP thermal storage units. AISI 316L stainless steel samples coated with Stellite-6 and Inconel-625 were tested for corrosion in NaNO3 containing SiO2 nanoparticles at 450 °C for 30, 60, and 90 days. Cross-section analysis was used to assess thickness loss, and coatings were analysed. Chemical attack enhanced material contrast for microstructural observation. Compositions of oxides were identified by EDS and XRD analysis, and ICP analysis identified elements in the salts after corrosion. Results showed almost no loss in thickness, even after 90 days, to substantiate the protective efficacy of coatings. Results confirm that Inconel-625 and Stellite-6 coatings are a reliable source of preventing corrosion caused by nanofluids in CSP thermal storage systems.