High-temperature corrosion behavior of Fe-Mo-Al alloys in H[sub 2]/H[sub 2]O/H[sub 2]S mixed-gas environments

Journal Article · Thu Apr 01 04:00:00 EST 1993 · Oxidation of Metals; (United States)

DOI:https://doi.org/10.1007/BF00665616· OSTI ID:5731853

Kai, W; Douglass, D L ^[1]

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1. Univ. of California, Los Angeles (United States)

The corrosion behavior of 11 Fe-Mo-Al ternary alloys was studied over the temperature range 700-980[degrees]C in H[sub 2]/H[sub 2]O/H[sub 2]S mixed-gas environments. With the exception of Fe-10Mo-7Al, for which breakaway kinetics were observed at higher temperatures, all alloys followed the parabolic rate law, despite two-stage kinetics which were observed in some cases. A kinetics inversion was observed for alloys containing 7 wt. % Al between 700-800[degrees]C. The corrosion rates of Fe-20Mo and Fe-30Mo were found to be reduced by five orders of magnitude at all temperatures by the addition of 9.1 or higher wt. % aluminum. The scales formed on low-Al alloys ([le] 5 wt % Al) were duplex, consisting of an outer layer of iron sulfide (with some dissolved Al) and a complex inner of Al[sub 0.55]Mo[sub 2]S[sub 4], FeMo[sub 2]S[sub 4], Fe[sub 1.25]Mo[sub 6]S[sub 7.7], FeS, and uncorroded FeAl and Fe[sub 3]Mo[sub 2]. Platinum markers were always located at the interface between the inner and outer scales for the low-Al alloys, indicating that outer-scale growth was due mainly to outward diffusion of cations (Fe and Al), while the inner scale was formed primarily by the inward flux of sulfur anions. Alloys having intermediate Al contents (7 wt. %) formed scales that consisted of FeS and Al[sub 2]O[sub 3]. The amount of Al[sub 2]O[sub 3] increased with increasing reaction temperature. The high-Al-content alloys (9.1 and 10 wt. %) formed only Al[sub 2]O[sub 3] which was responsible for the reduction of the corrosion rates. 17 refs., 18 figs., 2 tabs.

• OSTI ID: 5731853
• Journal Information: Oxidation of Metals; (United States), Journal Name: Oxidation of Metals; (United States) Vol. 39:3-4; ISSN OXMEAF; ISSN 0030-770X
• Country of Publication: United States
• Language: English

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01 COAL, LIGNITE, AND PEAT
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& Peat-- Gasification
02 PETROLEUM
020400 -- Petroleum-- Processing
36 MATERIALS SCIENCE
360100* -- Metals & Alloys
360105 -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
ALUMINIUM ALLOYS
CHEMICAL PLANTS
CHEMICAL REACTIONS
COAL GASIFICATION PLANTS
CORROSION
DATA
DISPERSIONS
EXPERIMENTAL DATA
FLUIDS
GASES
INDUSTRIAL PLANTS
INFORMATION
IRON ALLOYS
IRON BASE ALLOYS
MIXTURES
MOLYBDENUM ALLOYS
NUMERICAL DATA
PETROCHEMICAL PLANTS
PETROLEUM REFINERIES
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K