High temperature corrosion of stainless steel AISI 316L in molten nitrate salts based thermofluids for concentration solar plants

ABSTRACT

With the recent boom of environmentally friendly energies, the demand for materials capable of resisting certain working conditions demanded by these processes arises, for example, the obtaining of energy from sunlight, in which the Thermal storage is vital during the operation of the plant. In the present work, the reaction of AISI 316L steel in contact with molten nitrate salts (Ca (NO₃)₂ + NaNO₃ + KNO₃ and LiNO₃ + KNO₃ + NaNO₃) was evaluated, gravimetric tests were carried out with Two types of ternary salts of nitrates at a temperature of 600°C, evaluating the gain of mass in the steel, in turn, were carried out metallographic studies, in order to evaluate the damage of the microstructure. By means of SEM and optical micrographs, the morphology of the layer and the damage caused to the steel was observed. The surface where the greater aggressiveness of damage by the ternary salt in the steel was evidenced is the surface of the steel exposed to the lithium salt. The results of DRX yielded Fe_0.612Ni_0.388 and CrNi, as the main steel corrosion products, demonstrating that the salt fused with the calcium component is less harmful to the steel used in this project.

Keywords
corrosion; molten salts; high temperatures; solar salts