Hot corrosion failure mechanism of graphite materials in molten solar salt

Graphite materials are widely used in the metallurgical, chemical and defense industry due to their good thermal conductivity and chemical stability. Their chemical stability, in particular, leads to their greater application in storing and transporting the heat storage medium, Solar Salt, in solar thermal power generation. This paper adopted XRD, SEM and EDX to study the hot corrosion failure mechanisms of four kinds of graphite in molten Solar Salt which were produced with different raw materials and molding processes. The results show that the degrees of graphitization of sample 3, sample 4, sample 1, and sample 2 are respectively 85.03%, 82.80%, 80.70% and 79.92%; The higher the degree of graphitization, the better the hot corrosion resistance of the graphite to molten Solar Salt. The corrosion failure of graphite in the molten Solar Salt is mainly caused by the molten salt molecules infiltrating into the micro pores of the graphite which remain inside the graphite after cooled, causing its shrinkage, crack and deformation. There is no chemical reaction between the molten Solar Salt and the graphite, nor is there any new phase generated in the corrosion process.