Spray-graphitization against molten salts corrosion for concentrated solar power plants

Abstract

Molten salts are currently used at concentrated solar power (CSP) plants for thermal energy storage (TES) purposes. However, high-temperature corrosion by molten salts has detrimental effect on the investment costs and safety. This is particularly important for next generation CSP plants, where expected operational temperatures are very high. To enhance the durability of the CSP plantś components, while decreasing the production cost of electricity, the graphitization anticorrosion method for carbon steel A516.Gr70 (CS) in contact with molten binary nitrate salt and for stainless steel 310 (SS310) in contact with ternary carbonate salt is proposed in this work. To shed some light on the corrosion mechanisms and quantify corrosion rates a combination of SEM, EDX and XRD was applied. It was demonstrated that spray-graphitization anticorrosion method improves the compatibility of carbon steel A516.Gr70 and stainless steel 310 in direct contact with molten nitrate (390°C) and molten carbonate (600°C) salts, respectively. It was demonstrated that the presence of graphite on the surface of carbon steel or SS310 results in the formation of carbide/carbonate phase, which stabilizes the corrosion layer and prevents its peel-off, reducing the corrosion rate.