Influence of corrosion-resistant coatings on the post-corrosion thermal stability and fouling of molten salts for high temperature thermal energy storage

Corrosion and dissolution of containment alloy constituents is an important consideration in high temperature thermal energy storage using molten salts. While the focus of most studies has been on protecting the alloys from corrosion attack, an often-neglected aspect is the dissolution of alloy materials into the molten salt which leads to fouling and possible deterioration of the thermophysical properties of heat transfer fluids and storage media. This article considers the thermal stability and fouling of molten nitrate, carbonate, and chloride eutectic salts exposed to ferrous and nickel alloys with and without corrosion-resistant coatings at high temperatures. The melting temperature and thermal stability of the molten salts were measured using DSC and TGA analysis, while the dissolution of alloy or coating constituent elements in the molten salts was determined using the ICP-MS method. The study represents the first-ever report of post-corrosion characteristics of molten nitrate eutectic, carbonate eutectic, and chloride eutectic salts and a means of significantly reducing both corrosion of alloys and fouling of molten salts at high temperatures, by the use of fractal-textured Ni coatings.