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Iron calcium carbonate instability: structural modification of siderite corrosion films

DOI: 10.1021/acsami.0c14513 DOI Help

Authors: Adriana Matamoros-veloza (University of Leeds) , Richard Barker (University of Leeds) , Silvia Vargas (BP America, Inc) , Anne Neville (University of Leeds)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Acs Applied Materials & Interfaces

State: Published (Approved)
Published: October 2020
Diamond Proposal Number(s): 21717

Abstract: Corrosion research related to CO2-containing environments has focused over the past few decades on siderite formation (FeCO3) as a main corrosion product on carbon steel, yet the influence of Ca and other ions on its chemical and structural characteristics is not fully understood. Metal-localized corrosion is the biggest industrial challenge because of the unknown and unpredictable character of this phenomenon that frequently leads to failure. We report here the role of Ca and formation of iron-calcium carbonate (FexCayCO3) through a spiral growth model as in the calcite system and quantify the replacement of Fe2+ by Ca2+ ions in the structure of FeCO3 to form FexCayCO3. The incorporation of Ca2+ inhibits the completion of spiral segments on the growth of the rhombohedral crystals of FeCO3, promoting an enlargement of its structure along the c-axis. This leads to distortions in the chemical structure and morphology affecting the chemical and mechanical properties. Under flow conditions over time in an undersaturated environment, Ca is leached out from the expanded structure of FexCayCO3 increasing the solubility of the crystals, weakening the mechanical properties of the resulting corrosion films and stimulating localized corrosion.

Journal Keywords: corrosion; siderite; FexCayCO3; iron carbonate; iron calcium carbonate

Subject Areas: Materials, Chemistry

Instruments: I18-Microfocus Spectroscopy