Evaporated Alkali Carbonate Effect on an Aluminum Diffusion Coated 253MA Vessel after 4000 h Discontinuous Operation-Lessons Learned

A vessel of a laboratory setup for hosting molten alkali carbonate immersion experiments was recently decommissioned after about 4000 h discontinuous operation at 800 degrees C. In this article, we want to describe the long-term damage of the vessel caused by evaporated alkali carbonate species in a carbon dioxide gas environment. The vessel is made of alloy 253MA and coated by an aluminum powder pack diffusion process. The degree of material loss and internal degradation did not correlate with the temperature profile across the vessel but rather with the vicinity to the gas and salt evaporation source. One millimeter of the vessel's initial 5 mm wall thickness was completely consumed at the strongest attacked location plus another 800 mu m of internal attack beneath the metal-oxide interface.