Stainless steel 316 was examined for compatibility with the eutectic mixtures of NaCl + Na2CO3 and NaCl + Na2SO4 at 700 degrees C and Li2CO3 + K2CO3 + Na2CO3 at 450 degrees 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 degrees C. The attack morphology on the surface was uniform corrosion with no localized degradation at 450 degrees C. Microscopy observations showed grain boundary oxidative attack as the primary corrosion mechanism at 700 degrees C with depletion of alloying elements from grain boundaries.