Corrosion Monitoring Assessment on Lithium Nitrate Molten Salts as Thermal Energy Storage Material Applied to CSP Plants

Abstract

The development of the new generation of concentrated solar power (CSP) plants requires improvements in the thermal energy storage systems, and corrosion produced is one of the main challenges to control since this can affect the costs of the electrical generation. Electrochemical impedance spectroscopy (EIS) has been applied in this research as a corrosion monitoring technique, comparing the results with conventional gravimetric corrosion tests. Gravimetric and electrochemical tests were conducted using AISI 304 stainless steel immersed in a ternary salt mixture composed of 57 wt% KNO3 + 13 wt% NaNO3 + 30 wt% LiNO3 at 550 °C for 1000 h. The corrosion rate obtained using gravimetric and electrochemical tests was 7.8 μm/year and 5.7 μm/year, respectively. According to the results obtained in this research, EIS techniques could be a feasible option to control corrosion in CSP plants and reduce operational risks during the molten salt thermal-electricity conversion.