Early stages of sulfidation of iron and iron-chromium alloy in hydrogen sulfide

Technical Report · Thu Jul 01 00:00:00 EDT 1982

OSTI ID:6541051

Narayanacharyulu, P B.V.

Sulfidation of polycrystalline iron and an Fe-25 wt % Cr alloy at various partial pressures of H/sub 2/S in the temperature range of -170/sup 0/C to 500/sup 0/C was studied in situ in an ESCA spectrometer, and the sulfidized layers were investigated by depth profiling in an Auger spectrometer. The role of surface oxygen during sulfidation was investigated. The mode of sulfidation of sputter-clean iron was found to involve several stages: associative adsorption of H/sub 2/S at low temperatures, dissociative adsorption of H/sub 2/S at around ambient temperature, and the formation of first a sulfur-deficient iron sulfide and then stoichiometric FeS at slightly elevated temperatures as the H/sub 2/S pressure or the time of exposure was increased. Iron sulfides are more readily formed on the oxidized iron surface than on the sputter-clean surface. Chromia (Cr/sub 2/O/sub 3/) was found to be stable in an H/sub 2/S atmosphere at T less than or equal to 250/sup 0/C, but was converted to chromium sulfide at 300/sup 0/C. Chromium sulfide is more readily formed on the clean alloy surface than on the oxidized surface. During annealing in vacuum, there is surface chromium enrichment on the FeCr alloy, and this is enhanced in the presence of oxygen or sulfur on the surface. Sulfidation proceeds primarily by cation diffusion, and the growth of the sulfide layers was found to be more dependent on temperature than on time of exposure. Iron was found to be more mobile than chromium in the FeCr alloys.

• Research Organization: Ames Lab., IA (USA)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 6541051
• Report Number(s): IS-T-1016; ON: DE83004969
• Resource Relation: Other Information: Thesis. Submitted to Iowa State Univ., Ames
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHROMIUM ALLOYS
SULFIDATION
IRON
IRON BASE ALLOYS
ADSORPTION
ANNEALING
CHEMICAL REACTION KINETICS
CHROMIUM OXIDES
ELECTRON SPECTROSCOPY
HIGH TEMPERATURE
HYDROGEN SULFIDES
IRON SULFIDES
LOW TEMPERATURE
MEDIUM TEMPERATURE
TEMPERATURE DEPENDENCE
ALLOYS
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
ELEMENTS
HEAT TREATMENTS
HYDROGEN COMPOUNDS
IRON ALLOYS
IRON COMPOUNDS
KINETICS
METALS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SORPTION
SPECTROSCOPY
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
360105* - Metals & Alloys- Corrosion & Erosion