High temperature sulfidation of Fe‐Mn alloys and Mn in H2‐H2S

Abstract
The sulfidation behaviour of a range of Fe‐Mn alloys and pure Mn were studied at 973 K, 1073 K, and 1173 K in H2‐H2S atmospheres at constant pS2 or constant pH2S/pH2. The sulfidation kinetics were parabolic in most cases, but two different diffusion processes affect the kinetics. In the sulfidation of the Fe‐Mn alloys at 973 K and 1073 K, the diffusion of manganese atoms in the alloy is the rate‐determining step and an interlocked scale/alloy interface is observed. At 1173 K there is a transition to rate‐control by the diffusion of manganese in the sulfide scale connected with transition from rugged to a planar scale/alloy interface.