Corrosion of structural materials for salt melt technologies

Molten salt mixtures are considered media for many modern technologies using their ability to store thermal energy, thermal stability at high temperatures, low melting point, and other properties. The disadvantage of their use is high corrosion aggressiveness towards metal structural materials. In particular, impurities contained in salt mixtures can significantly increase the corrosion rates of alloys. This paper compares the corrosion behaviour of Inconel 625, 321, 316L and 316Ti alloys in a mixture of chloride and nitrate salt melts. The parameters in which both mixtures are stable and in melt form were chosen -400 °C, an inert argon atmosphere, and a pressure of 0.2 MPa. After exposure, the state and composition of the surfaces were analysed by XPS (X-ray photoelectron spectroscopy) and SEM (Scanning Electron Microscopy). These materials are better suitable for nitrate salt environments, where only very thin surface layers were formed without local types of corrosion. In chloride melts, Alloy 321 and Inconel 625 have shown greater resistance than 316L and 316Ti stainless steels.