The corrosion of the Ni foil in molten FLiNak was monitored for 4 hours, and the XANES spectra was analyzed to determine the concentration and oxidation state of the corrosion products. The results from this experiment are displayed in Fig. . The XANES spectra in Fig. show a clear increase in the Ni concentration, and the fine structure initially shows a purely Ni 2+ valence state, with structure near-identical to Fig. . The XANES spectra are thus suited to quantify concentration, structure, and oxidation state , which proves to be useful to understand how the foil interacts with the salt. These results show that the Ni 2+ concentration in the salt initially increased and then plateaued. A finite Ni 2+ content at time zero is due to pre-beamtime baking and slight Ni leach- ing during sample preparation. The XANES spectra after about an hour started to show an increase in a pre-edge feature indicative of metallic Ni as seen in the top panel in Fig. . A majority of the signal was attributed to metallic Ni after about 3 hours as seen in the bottom panel of Fig. . The LCA results in Fig. identify this transition with a sharp increase in the metallic Ni concentration after 1.5 hours that eventually decreases.