Abstract:
The behavior of Haynes 230 and NS-163 alloys in fluoride (FLiNaK) and chloride (MgCl2-KCl) salts as well as NS-163 and Incoloy 800H alloys in MgCl2 salt were evaluated based on thermodynamic analysis. Also, corrosion behavior of alloys with the addition of corrosion inhibitors (Zr and Mg) to the molten salts were investigated in this paper. Corrosion studies were performed using thermodynamic modeling software to understand the corrosion mechanisms and to investigate the compatibility of Haynes and Incoloy alloys for thermal storage applications in the molten salts. Equilibrium conditions were considered for predicting the corrosion products, corrosion potentials and decomposition of molten salt with and without inhibitor for Haynes 230 and NS-163 alloys in FLiNaK and MgCl2-KCl at 700, 750, 800, 850, 900 and 1000oC. The same procedure was applied for NS-163 and Incoloy 800H alloys in MgCl2 at 750, 800 and 850oC. Results illustrate these alloys are all stable in the molten salt. From calculation, K3AlF6 and MnCl2 are the major products observed in FLiNaK and chloride salts respectively. In addition, corrosion inhibitors (Zr and Mg) protect these alloys from further corrosion acting as sacrificial anode. Furthermore, with known amount of impurities added into molten salt, calculations show that Cr and Mn metals are transferred to molten salt readily. Experiment of Haynes 230 and Stainless Steel corrosion in FLiNaK were performed at 1000oC under 1 bar Ar atmosphere for 1000 hours and NS-163 for 720 hours to detect the corrosion rate. SEM was performed to evaluate the corrosion mechanism for these alloys.
