Corrosion Behavior of Silicon Nitride, Magnesium Oxide, and Several Metals in Molten Calcium Chloride with Chlorine

Corrosion studies are described in a molten calcium chloride environment sparged with chlorine gas at 850°C, both in the melt and in the gas phase above the salt, in support of efforts at Westinghouse Savannah River Company to develop more resistant materials of construction for molten salt processing of plutonium. Corrosion rates and electron microscope analyses are reported for Inconel alloys 601 and 617, tantalum, tungsten, magnesium oxide, and silicon nitride. Silicon nitride exhibited the greatest resistance, showing <0.1 mg/cm²·h loss in both melt and vapor. None of the metallic coupons withstood the chlorine vapor environment, although Inconel indicated resistance immersed in the melt if protected from chlorine gas.