Formation and oxidation of sulfides on pure iron and iron oxides

Formation of pyrophoric iron sulfide (PIS) on the inside-walls of molten sulfur, crude oil or asphalt tanks is the problem to be solved to avoid accidental explosions in petroleum industries. In this study, pure Fe, Fe3O4 and Fe2O3 were sulfidized in Ar-H2S atmosphere, and the sulfidized products formed were observed and analyzed. Furthermore, sulfidized specimens were oxidized in Ar-O-2 atmosphere to study their oxidizing behavior. Sulfide formed on pure Fe was a dense and uniform film of FeS. On the contrary, sulfide films formed on Fe3O4 and Fe2O3 were porous FeS2. Oxidation of FeS2 formed on iron oxides occurred rapidly, while oxidation rate of FeS formed on iron was much slower. The experimental results suggest that FeS2 formed on iron oxides may act as a PIS.