316L stainless steel corrosion in molten salts NaNO3 KNO3 NaNO2 simulating storage conditions

A wide variety of stainless steel is used in concentrated solar plants in different elements as pipelines, pumps, storage tanks, among others, and these are in contact with molten salts, which are used as thermal energy transfer fluids. In this paper, corrosion of stainless steel AISI 316L in molten salt NaNO3 - NaNO2 - KNO3 has been investigated at temperatures of 450, 500 and 550 degrees C, for an exposure period of 150 hours. The salt mixture is sprayed by spray onto the surface of 316L stainless steel, which has been preheated to 170 degrees C. To obtain a thin layer of salt on the samples, these are carried to the furnace in the presence of an oxidizing atmosphere at high temperature for 1, 3, 10, 30, 100 and 150 hours. The results of mass gain and characterization by SEM-EDS and XRD of the surfaces showing the formation of a passive film, composed mainly of hematite Fe2O3. The thickening of the oxide film is according to a parabolic law, whose speed depends on the temperature of the melt.