Stainless steel 316 was examined for compatibility with the eutectic mixtures of NaCl + Na2CO3 and NaCl + Na2SO4 at 700 °C and Li2CO3 + K2CO3 + Na2CO3 at 450 °C in air for thermal energy storage. Electrochemical measurements combined with advanced microscopy and microanalysis techniques were employed. NaCl + Na2CO3 was found as the most aggressive salt at 700 °C. The attack morphology on the surface was uniform corrosion with no localized degradation at 450 °C. Microscopy observations showed grain boundary oxidative attack as the primary corrosion mechanism at 700 °C with depletion of alloying elements from grain boundaries.