The role of Ca2+ ions on Ca/Fe carbonate products on X65 carbon steel in CO2 corrosion environments at 80 and 150 °C

•The addition of 1.83 wt.% Ca2+ at 80 °C led to the precipitation of thicker and less protective corrosion product layers consisting of FexCayCO3.•The addition of Ca2+ ions at 80 °C accelerated pit growth. Greater uniform corrosion rates were also observed, owing to the establishment of a less prote...

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Bibliographic Details
Published in:Corrosion science 2019-08, Vol.156, p.58-70
Main Authors: Shamsa, Amir, Barker, Richard, Hua, Yong, Barmatov, Evgeny, Hughes, Trevor L., Neville, Anne
Format: Article
Language:English
Subjects:
Calcium carbonate
Calcium ions
Carbon dioxide
Carbon steel
Carbon steels
Carbonates
CO2 corrosion
Concentration gradient
Corrosion
Corrosion effects
Corrosion environments
Corrosion prevention
Corrosion products
Corrosion rate
High temperature
Ion beams
Iron carbonate
Localized corrosion
Mixed carbonate
Pitting (corrosion)
Uniform attack (corrosion)
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Summary:•The addition of 1.83 wt.% Ca2+ at 80 °C led to the precipitation of thicker and less protective corrosion product layers consisting of FexCayCO3.•The addition of Ca2+ ions at 80 °C accelerated pit growth. Greater uniform corrosion rates were also observed, owing to the establishment of a less protective corrosion product layer.•The influence of Ca2+ ions was less substantial at 150 °C which establishes that mixed carbonates such as FexCayCO3 can be as protective as FeCO3 if precipitated under the right conditions.•The stoichiometry (x and y) of iron-calcium carbonate (FexCayCO3) corrosion products can exist with concentration gradients across their depths. The role of Ca2+ ions on the corrosion behaviour of carbon steel in CO2-corrosion environments was evaluated at 80 °C and 150 °C. In the presence of Ca2+ ions there was a more significant effect on the general corrosion rate at the lower temperature of 80 °C where the protection afforded by the corrosion product layer was reduced. The extent of localised/pitting corrosion increased through the addition of Ca2+ ions indicating that Ca2+ plays a role in promoting localised corrosion. XRD based calculations, along with focused ion beam EDX-line scans confirmed that the mixed Ca/Fe carbonates precipitated with concentration gradients across their thicknesses.
ISSN:0010-938X
1879-0496
DOI:10.1016/j.corsci.2019.05.006