The effect of Cl, Br, and F on high-temperature corrosion of heat-transfer alloys

The impact of small alkali halide additions on the melting behavior and corrosivity of a synthetic sulfate deposit at 500, 550, and 600 degrees C was investigated. Three differently alloyed commercial heat-transfer materials; low -alloyed 10CrMo9-10, stainless AISI 347, and high-alloyed Sanicro 28, were studied. The samples were exposed for 168 h in a tube furnace to a K2SO4 + Na2SO4 mixture containing 0.85 mol% KCl, KBr, or KF. The extent of material degradation was determined by weight loss measurements, while the morphology, thickness, and composition of the formed oxide scale were characterized with SEM-EDS. Additionally, the melting behavior of the mixtures was studied with TG-DTA. It could be concluded that already small amounts of reactive alkali halides in an otherwise inert K2SO4 + Na2SO4 mixture change significantly the corrosion and melting behavior of the mixture.

Automated summary

The study investigated the impact of small alkali halide additions on the melting behavior and corrosivity of a synthetic sulfate deposit at temperatures of 500, 550, and 600 degrees C. Three different alloyed commercial heat-transfer materials were studied. It was found that even small amounts of reactive alkali halides significantly changed the corrosion and melting behavior of the mixture.