Corrosion behavior of Incoloy 840 in molten nitrate salt for CSP plants

As the tube materials of receiver in the solar tower power plant, molten salt corrosion behavior of Incoloy 840 has been studied. In this work, after Incoloy 840 samples were deposed separately in molten Solar Salts (40wt.% KNO₃ + 60wt.% NaNO₃) at 560°C for different times (5, 10, 15, 20, 30, 40, 60 and 80h), the weight-loss of samples were measured, the metallurgical structure of as-received Incoloy 840 was observed by optical microscope, the metallurgical structure of corroded films on the samples were observed by SEM, the corrosion products chemistries of the oxide film were analyzed by EDS and XRD. The results showed that the corrosion kinetics of the Incoloy 840 follows typical parabolic rule at 560°C in mixture molten salts (40wt.% KNO₃ + 60wt.% NaNO₃), and the corrosion rate of Incoloy 840 is 12.3 μm/year. The corroded films had a bilayer structure, the outer layer consists of Fe₂O₃, and the inner layer consists of γ-(Fe, Ni) and Cr₂O₃.