Molten Chloride Salts for Thermal Energy Storage in Next Generation CSP: Acceptable Salt Impurity Level for Metallic Corrosion Control

Abstract

In this work, an advanced titration process based on the developed acid consumption titration method in previous work is investigated and used for chemical post-analysis of the MgOHCl concentration in the MgCl2-containing molten chlorides. Compared to the existing titration methods in, this advanced titration process can avoid the negative effect of dissolved MgO in the molten salt on the measurement accuracy. Both the measurement limit and accuracy are improved to the ppm level - the target concentration level regarding the salt corrosivity. Furthermore, the electrochemical method based on cyclic voltammetry for in-situ monitoring MgOHCl concentration developed previously is calibrated using this advanced titration process to improve its measurement accuracy and precision. Both methods for impurity concentration measurements as well as the methods for corrosion rate measurements will be used to investigate the acceptable impurity levels for selected low-cost structural materials such as high-temperature stainless steels for e.g. molten salt storage tanks in TES applications.