High-Temperature Corrosion Behavior of Superalloys in Molten Salts - A Review

The use of molten salts based on fluorides/chlorides/nitrates/sulfates or carbonates is now an accepted practice in energy conversion technologies and many other industrial processes. However, compatibility of molten salts with the structural alloys and materials corrosion has been of real concern at such temperatures (600-900 degrees C). Hence, the material development and corrosion studies turn out to be an essential part of research. The results of recent studies are reviewed to understand the developments that have occurred in the latter part of the last decade. The corrosion kinetics of modern materials in variety of molten salts with focus on reaction mechanisms and corrosion products is investigated by scientists around the globe. Emphasis has also been given on the composition of the oxide films/corrosion products on alloys of interest in wide a range of melts. By and large, molten salt corrosion has been predominantly studied by gravimetric, electrochemical techniques and, morphology and chemical analysis of corrosion products by means of XRD, SEM/EDX, ICP/AAS, etc. This article gives in-depth insight into the composition of materials, the molten salt mixtures, and various aggressive environments mainly high temperatures and long exposures.