On the oxidation of iron in CO sub 2 + CO mixtures. 3: Coupled linear parabolic kinetics

Journal Article · Thu Aug 01 04:00:00 EDT 1991 · Oxidation of Metals; (United States)

OSTI ID:6024829

Bredesen, R; Kofstad, P ^[1]

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1. Univ. of Oslo (Norway)

High-purity iron has been oxidized at 1,000-1,200C in CO{sub 2} and in CO{sub 2} + CO with different compositions and at different total gas pressures (0.1-1 atm.). The experimental work has comprised thermogravimetric reaction rate measurements and characterization of the wuestite scales by metallography and x-ray diffraction. The overall results have been analyzed in terms of a classical model for coupled linear/parabolic kinetics, where it is assumed that the surface of growing wuestite scales has exactly the same defect structure and defect concentrations as that of bulk wuestite equilibrated in the same gaseous atmospheres. Important discrepancies are found between the predicted and the experimentally observed reaction behavior. Thus, both the linear and parabolic rate constants are found to be dependent on the partial pressure of CO{sub 2} and the total gas pressure of the CO{sub 2} + CO gas mixtures, and furthermore, the reaction in CO{sub 2} + CO is slower than in O{sub 2} and in H{sub 2}O + H{sub 2} with the same oxygen activity. In order to explain the experimental results, it is suggested that CO and CO{sub 2} molecules interact with the wuestite surface and thereby affect the defect structure and defect concentrations in a thin surface layer, and that this, in turn, affects both the linear and parabolic reaction rates.

• OSTI ID: 6024829
• Journal Information: Oxidation of Metals; (United States), Journal Name: Oxidation of Metals; (United States) Vol. 36:1-2; ISSN 0030-770X; ISSN OXMEA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COHERENT SCATTERING
CORROSION PRODUCTS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DATA
DIFFRACTION
ELECTRON MICROSCOPY
ELEMENTS
EQUATIONS
EXPERIMENTAL DATA
GRAVIMETRIC ANALYSIS
INFORMATION
IRON
KINETIC EQUATIONS
KINETICS
LOW PRESSURE
MATHEMATICAL MODELS
MEDIUM PRESSURE
METALLOGRAPHY
METALS
MICROSCOPY
NUMERICAL DATA
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PRESSURE DEPENDENCE
QUANTITATIVE CHEMICAL ANALYSIS
REACTION KINETICS
SCANNING ELECTRON MICROSCOPY
SCATTERING
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
TRANSITION ELEMENTS
VERY HIGH TEMPERATURE
X-RAY DIFFRACTION