Material Technology

Investigation of iron sulfide surface layer growth in aqueous H2S/CO2 environments

Svenningsen, G. , Palencsár, A. , Kvarekvål, J.
Corrosion 2009, Atlanta, 2009-03-22-03-26. Paper 09359
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The nature of the iron sulfide films formed on steel surfaces during H2S/CO2 corrosion is a key parameter for pH stabilisation in sour gas pipelines, and will also affect the efficiency of corrosion inhibitors. On this background, a series of systematic experimental studies of iron sulfide corrosion film growth in aqueous H2S/CO2 environments have been initiated. This contribution presents results obtained in the initial stages of these studies using gravimetric (mass loss) methods, FE-SEM and EDS. X65 carbon steel samples were exposed to sour conditions for various periods of time up to 10 days. Evidence of iron sulfide layer formation governed by the parabolic film growth rate law was found for the test conditions reported, indicating that the corrosion and film growth rates in these cases were limited by the electronic conductivity of the film or mass transport, probably Fe2+ diffusion, across the corrosion film. Assessment of the films by SEM revealed that the morphology changes with exposure time within the range studied. ©NACE International. All rights reserved. Paper reproduced with permission from CORROSION 2009 Annual Conference and Exhibition, Atlanta.
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