A kinetic model for calculating concentration profiles and fluxes of CO{sub 2}-related species across the Nernst diffusion layer
- Univ. of Oslo (Norway)
The aggressive behavior of carbonic acid solutions upon various steels has been widely investigated, but is yet not fully understood. In order to achieve more knowledge of the mechanisms of CO{sub 2} corrosion, simultaneous diffusion and homogeneous chemical reactions have been simulated close to a corroding iron electrode, using kinetic data for the reactions involving CO{sub 2}-related species and water. Many CO{sub 2} corrosion models predict mass transfer across the stagnant diffusion layer without considering contributions from homogeneous chemical reactions. However, such reactions play a significant role when the equilibria of the CO{sub 2}/H{sub 2}O system are disturbed by concentration changes caused by diffusion. Attempts have been made to treat this phenomenon, using equilibrium constants in the routines involving chemical terms. Still, this thermodynamic approach fails to determine the concentration changes caused by chemical reactions, as equilibria will not always be obtained. The recent model simulates the conditions in the stagnant layer close to a dissolving iron surface, on which heterogeneous reduction of H{sup +}-ions and H{sub 2}CO{sub 3} occurs. One-dimensional diffusion is calculated using a finite element method. Homogeneous chemical reaction rates are determined from rate constants and differential or integrated rate expressions. The diffusion/reactions computation procedure is iterated until convergence is reached. The results are compared to published corrosion rates.
- OSTI ID:
- 504729
- Report Number(s):
- CONF-970332-; TRN: IM9733%%144
- Resource Relation:
- Conference: Corrosion 97. 52. annual corrosion conference of the National Association of Corrosion Engineers: economics and performance - bridging the gap and NACExpo, New Orleans, LA (United States), 9-14 Mar 1997; Other Information: PBD: 1997; Related Information: Is Part Of Corrosion/97 conference papers; PB: [4584] p.
- Country of Publication:
- United States
- Language:
- English
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