A Materials Screening Test of Corrosion Monitoring in LiNO3 Containing Molten Salts as a Thermal Energy Storage Material for CSP Plants

Abstract

Concentrated solar power (CSP) plants, in the context of thermal energy storage (TES) upgrades, need to provide a timely and effective response to the corrosion process that occurs due to the effect of high temperatures, where one of the main challenges is to control its effect, and thus the costs related to the materials used. Electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) were applied in this study as a corrosion monitoring technique. The electrochemical tests were carried out on the materials AISI304, AISI430, and HR-224 immersed in a mixture of ternary salt composed of 57 wt.% KNO3 + 13 wt.% NaNO3 + 30 wt.% LiNO3 at 550 °C during 100 h of exposure and subsequently compared with solar salt. The test was also carried out on the VM12 alloy in the ternary salt with lithium content at 100 and 1000 h of exposure at 550 °C. The corrosion tests show that the materials conform to a model of protective layer in which the same results were contrasted with the chemical corrosion mechanism of nitrate mixture. According to the results obtained in this research, electrochemical techniques could be an interesting option to control corrosion in CSP plants and reduce operational risks during operation.

The Effect of Long-Term Corrosion on a Molten Salt Pump in Contact With a Ternary Mixture in a CSP Plant

“…This corrosion effect relates to the concentration of oxides produced by ionic reactions in the electrolyte and different atmospheric conditions in the medium. Therefore, the molten salts at high temperatures eliminate the oxide layers in the container materials, which in some instances could act as a protective layer [20], a topic that deserves further investigation.…”