Corrosion and mechanical assessment in LiNO_3 molten salt as thermal energy storage material in CSP plants

摘要

The development of solar thermal energy in Chile, leads to the realization of applied research in such a way that new technologies and applications suitable to the conditions of the Atacatna Desert can be proposed. In view of the search for new fluids feasible to be applied in CSP technology as thermal energy storage using molten salts, this research proposes the use of the mixture composed by 30wt. % LiNO_3 - 13wt. % NaNO_3 - 57wt. % KNO_3. Corrosion has been evaluated on different stainless steels (AISI430, AISI304, VM12-SHC) and a Ni base alloy (HR-224). In order to monitorize corrosion, electrochemical impedance spectroscopy and linear polarization technique have been applied in order to obtain the corrosion rate and the corrosion mechanism as well. The corrosion rates obtained for AISI304, AISI430, VM12 and HR224 was 1.82, 2.69, 3.53 and 0.63 (mm/year), respectively at 550°C and 100 h of immersion. Finally, the effect of molten salts on the mechanical properties of materials used in solar thermal plants is studied, as well as the effect of Flow Accelerated corrosion (FAC), determining the most suitable methods for these evaluations.