Radioactive Sulfur Oxide Studies of External Corrosion Reactions on Surfaces

Abstract

Radioactive sulfur-35 has been used as a tracer to determine the roles of SO2 and SO3 in reactions leading to formation of alkali iron trisulfates. The reactivity of 30 ppm SO3 with surfaces containing iron oxides, alone or mixed with alkali sulfates, has been found to be much greater than that of large amounts of SO2 + O2 over the temperature range 900 to 1300 deg F. The SO3 reactivity was found to be a maximum at 1200 deg F, while the SO2 reactivity was at a minimum about 1150 deg F. Complex sulfates were formed most readily with K2 SO4 -Fe2 O3 surfaces, followed by Na2 SO4 -steel, and Na2 SO4 -Fe3 O3 surfaces.