Effect of nitrate-carbonate molten salt flow rate for the 347H corrosion behavior

Abstract

Molten salts have been widely adopted for solar thermal power stations because of their superior thermophysical properties. However, the corrosive effect on the metal material with molten salt is an important factor for the long-term operation of CSP systems. For the study of the corrosive influence on metallic materials of molten salts in dynamic conditions, the corrosion performance of the 347H sample in molten salts at different flow rates was analyzed by using nitrate-carbonate molten salt as the base salt. The findings revealed a higher corrosion rate of the 347H samples under dynamic conditions, compared to static conditions. Moreover, as the flow velocity for the molten salt increases, 347H sample corrosion rates increase. The morphological analysis of the 347H sample revealed that, under molten salt static conditions, a dense corrosion layer was mainly formed in the 347H sample, while, under molten salt dynamic conditions, a grooved structure was observed in the 347H sample. The main corrosion products of 347H samples in different flow rates are composed of Fe2O3, Fe3O4, NiFe2O4 and NaFeO2. Therefore, for changing the molten salt flow rate, the sample’s corrosion morphology changes but does not affect the sample’s corrosion product type.