Enhanced corrosion resistance of alloy in molten chloride salts by adding nanoparticles for thermal energy storage applications

摘要

Because of the exceptional heat transfer characteristics, thermal-chemical stability, and thermal energy storage potential, molten salts are widely used in concentrating solar power (CSP) plants. However, corrosion induced by molten salt is a major factor affecting the safety of the system under long-term energy storage operation con-ditions, especially at high temperatures. In this work, chloride salt (NaCl-KCl-MgCl2) was considered as base salt for the preparation of nanocomposite salt using Al2O3 nanoparticles. The gravimetric method and other in-situ characterization technics were employed for the analysis of corrosion behavior, mass loss, surface microstruc-ture, and chemical composition of Inconel 625 alloy in base salt and nanocomposite salt at 500 to 700 degrees C temperature range. This study demonstrated the nanocomposite salt could slow down the corrosion of the Inconel 625 alloy in the high-temperature molten salt. The experimental results disclosed the mass loss and corrosion rate behavior of the Inconel 625 alloy immersed in nanocomposite salt which is lower than those of the Inconel 625 alloy immersed in base salt. The presence of Al2O3 nanoparticles results in a thinner corrosion layer of Inconel 625 alloy in nanocomposite salt. Through the corrosion mechanism analysis of Inconel 625 alloy in molten salt, it was found that the surface of corroded Inconel 625 alloy is characterized by a dense oxide layer mainly composed of MgCr2O4. The corrosion resistance mechanism of Inconel 625 alloy in nanocomposite salt was also analyzed, and the results showed that Al2O3 nanoparticles played an important role in the corrosion resistance of Inconel 625 alloy. This study provided innovative approaches to enduring the heat storage capacity of molten salt in concentrated solar power and other related thermal energy storage systems.