As a phase change material for solar energy storage at moderate- high temperature, the molten eutectic chloride salt of a sodium chloride and a magnesium chloride (NaCl-52 wt% MgCl2) is strongly corrosive to metal container and pipes. The corrosion behavior of three kinds of iron-chromium-nickel (Fe-Cr-Ni) alloys and a carbon steel in the molten eutectic salt at 520℃ were studied. Results show that the carbon steel is corroded along grain boundary for a iron atom become ferrous ion (Fe2+) and ferric ion (Fe3+). A thick and compact magnesium oxide (MgO) shell is formed on the carbon steel surface, which protects the specimen from corrosion. The MgO shell also formed on the three kinds of iron-chromium-nickel alloy surface, but the magnesium oxide shell can’t protect them from corrosion in the molten salt. Because a loose skeletal microstructure rich Ni is formed on specimen surface for the chromium element is preferentially corroded. The magnesium oxide (MgO) shell or particles peel off easily. In addition, the higher of the content of the chromium, the more serious of the corrosion As a vessel or pipe material for solar energy storage by molten chloride salt, a cheap iron-based alloy with alloy element nickel is more development prospects.