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The complete range of binary Fe-Mn alloys were sulfidized in pure sulfur vapor (1 atm) at 700-1000°C. It was found that the corrosion kinetics could be divided into four groups, depending upon the alloy concentration. The first group, up to 11 w/o Mn, had a constant corrosion rate. The second group, up to about 63 w/o Mn, had an exponentially decreasing rate of corrosion with increasing manganese content. In the third group, about 63-80 w/o Mn alloys, the corrosion rate did not follow the parabolic law. The corrosion rates became constant above 80 w/o Mn. These corrosion kinetics were explained by considering the scale structure and alloy substrate. [ABSTRACT FROM AUTHOR]

An Fe-27 w/o (weight %) Mn alloy was sulfidized at temperatures of 973, 1073, and 1173 K inflowing H/HS/N atmospheres corresponding to equilibrium sulfur pressures of 8 Pa. Steady-state parabolic kinetics were always observed after an initial period during which the instantaneous parabolic rate constant increased with time. Product scales were compact and consisted of a layer of Fe(Mn) S over an inner layer of α-Mn(Fe)S. Preoxidation led to a diminution in the subsequent sulfidation rate. Conflicts between differing reports in the literature of the kinetics of this reaction are resolved, and it is concluded that the protective effect expected of an α-MnS layer is in fact possible. [ABSTRACT FROM AUTHOR]

The diffusion processes occurring when binary alloys react with oxygen to form an oxide that contains both alloy components in solid solution, either exclusively as internal oxide or in combination with a surface scale, have been analyzed and compared with experimental results for Fe-Mn and Ni-Co alloys. The experimental results available for the Fe-Mn system were obtained under conditions of exclusive internal oxidation, and good agreement was obtained between calculated and experimental results. In the Ni-Co system, a surface scale and a zone of internal oxidation develop. Agreement between calculated and experimental depths of internal penetration is acceptable if the diffusivity of oxygen in the alloy is 3.8×10 cm/sec at 1100°C. Agreement between calculated and experimental concentration profiles is not very good. [ABSTRACT FROM AUTHOR]