Corrosion Ability of a Novel Heat Transfer Fluid for Energy Storage in CSP Plants

The enhancements in the storage systems developed by thermo solar centrals have provided to renewable energy a considerable increase in efficiency. This improvement also fosters the design of innovative storage fluids with lower melting point and thermal stability as new molten salts mixtures. In this research, the corrosive effects of a molten nitrate mixture composed by Ca(NO3)2–NaNO3–KNO3–LiNO3 were assessed at 390 °C on a carbon steel (A516) and on low-Cr alloy steels (T11 and T22). The corrosion rates were determined by gravimetric tests, measuring the weight gain during 2,000 h, identifying the corrosion products via scanning electron microscopy and X-ray diffraction. Study of T22 steel revealed a better behavior under corrosive environment, identifying the formation of MgCr2O4 protective spinels mainly. Fe2O3 and Fe3O4 were the others important products found on the tests performed at 390 °C, being observed also the formation of some stable compounds with the impurities of the salt, as carbonates and sulphates.