Study of corrosion by Dynamic Gravimetric Analysis (DGA) methodology. Influence of chloride content in solar salt

When a system for thermal energy storage (TES) is designed, many factors must be considered: storage time, dimensions, material to store heat, etc. Usually, molten salts are selected as TES materials because of their great thermal properties at high temperatures. When the whole TES system is going to be built, the material to be used for containing the thermal storage material becomes an important issue. It must have proper mechanical properties, withstand high temperatures and, above all, resist corrosion due to storage material, being in most of the cases, highly corrosive molten salt mixtures. To determine the corrosion on a metal plate, ASTM Standard-G1-03 procedure is usually applied, in which the corroded metal sample is submitted to several cycles including: attack by a chemical solution, washing, cleaning, drying, and weighing. In order to minimise the handling of the sample, a new methodology (Dynamic Gravimetric Analysis, DGA) has been developed and used to determine the corrosion produced in carbon steel A516Gr70 samples induced by different salt mixtures commonly used as molten salts containing different amounts of chloride, at working temperatures conditions. The results show that the higher is the content of chloride in molten salts the greater is the steel loss produced by corrosion and makes the corrosive kinetics to be highly increased when it is overtaken.