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TitleIn-situ synchrotron XRD studies of CO2 corrosion of carbon steel
Publication TypeConference Paper
Year of Publication2012
AuthorsKo, M., Ingham B., Laycock N., Burnell J., and Williams D.E.
Conference NameAnnual Conference of the Australasian Corrosion Association 2012
Date Published2012
KeywordsAnodic dissolution, Anodic potentials, Carbon dioxide, Carbon steel, Corrosion, Dissolution, Dissolution rates, In-situ synchrotrons, Induction periods, Iron ores, Lasers, Saturated solutions, Siderite, Small concentration, Steel, Synchrotrons, X ray diffraction
AbstractIn-situ synchrotron x-ray diffraction was used to determine the structure and composition of the surface scale formed on carbon steel in CO2 saturated solutions at 80°C under anodic polarisation. The results showed a significant induction period before siderite precipitation, which directly correlated with a rise in the current density to a point when a sufficiently coherent scale is formed. The addition of small concentrations of MgCl 2 accelerated the scale formation and caused the formation of Fe 2(OH)2CO3 along with siderite. At pH between 4.2 and 6.8 with applied anodic potentials from -700 mV to -600 mV vs. SCE (rest potential (Ecorr) = -775 mV to -725 mV), the anodic dissolution of mild steel is accelerated by decreasing pH. Siderite is precipitated when a critical local supersaturation near the surface is achieved. The onset of siderite precipitation causes local acidification of the solution and accelerates the dissolution rate of the steel until a coherent protective scale is formed. Copyright © (2012) by the Australasian Corrosion Association.

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