The sulfidation of two-phase Fe-Cu alloys in H{sub 2}-H{sub 2}S mixtures at 500--700 C

Journal Article · Wed Dec 01 04:00:00 EST 1999 · Oxidation of Metals

DOI:https://doi.org/10.1023/A:1018808031575· OSTI ID:684333

Castello, P; Gesmundo, F ^[1]; Niu, Y ^[1]; Stott, F H ^[2]

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1. Univ. di Genova (Italy). Ist. di Chimica
2. Univ. of Manchester Inst. of Science and Technology (United Kingdom). Corrosion and Protection Centre

The sulfidation behavior of three two-phase Fe-Cu alloys containing 25, 50, and 75 wt.% copper has been investigated in H{sub 2}-H{sub 2}S mixtures at 500--700 C under gas-phase sulfur pressures, which is significantly above those for the dissociation of both FeS and Cu{sub 2}S. In all cases, the three alloys sulfidized more slowly than both pure metals under the same conditions. At all temperatures, Fe-25 Cu showed the slowest growth rates, whereas Fe-50Cu sulfidized more rapidly than the other two alloys. However, the kinetics curves for the three alloys tended to overlap, particularly at the higher temperatures. The scales were complex and contained an outer layer composed of a mixture of two different Cu-Fe double sulfides, Cu{sub 5}FeS{sub 4} and CuFeS{sub 2}, plus an inner zone containing a mixture of metallic iron with the double-sulfide Cu{sub 5}FeS{sub 4} formed by complete sulfidation of the copper-rich phase and partial sulfidation of the iron-rich phase. This region also contained large voids, possibly because of outward diffusion of metal cations, whereas the iron-rich islands were mainly unattacked. The depth of internal attack increased with increasing temperature and/or iron content. Finally, particles of almost pure copper metal, probably formed during cooling from the reaction temperature, were present at the scale-subscale interface, as inclusions in the scale and as whiskers protruding out of the external scale surface.

• OSTI ID: 684333
• Journal Information: Oxidation of Metals, Journal Name: Oxidation of Metals Journal Issue: 5-6 Vol. 52; ISSN OXMEAF; ISSN 0030-770X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHEMICAL COMPOSITION
COPPER ALLOYS
HYDROGEN
HYDROGEN SULFIDES
IRON ALLOYS
KINETICS
SCALING
SULFIDATION
TEMPERATURE RANGE 0400-1000 K