Anti-corrosion characteristics of FeCO3 and FexCayMgzCO3 scales on carbon steel in high-PT CO2 environments

Wang, C; Hua, Y; Nadimi, S; Hu, Q; Taleb, W; Zhang, J; Liu, X; Zhang, R; Chen, X; Neville, A; Lia, Y

doi:10.1016/j.cej.2021.133484

Anti-corrosion characteristics of FeCO₃ and Fe_xCa_yMg_zCO₃ scales on carbon steel in high-PT CO₂ environments

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Abstract

Corrosion products formed on carbon steel can be considered as naturally occurring anti-corrosion scales. However, relationships between porosity and anti-corrosion characteristics of such scales remain poorly understood. In this study, characterisation data derived from focus ion beam (FIB) and X-ray micro-computed tomography (μCT) techniques, combined with image processing algorithms, were applied to reveal the porosity, pore connectivity and pore size distribution within FeCO₃ and Fe_xCa_yMg_zCO₃ (where x+y+z=1) scales on a X65 carbon steel substrate. The formation kinetics, chemistry and anti-corrosion capabilities of both scales were also systematically evaluated by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), profilometry and electrochemical measurements. The results demonstrate that FeCO₃ scales can reduce the availability of active surface areas more efficiently with their lower porosity on the steel surface, providing superior anti-corrosion performance than Fe_xCa_yMg_zCO₃ scales. This study elucidates the effects of ubiquitous cations on the formation and relative protectiveness of corrosion product scales, as well as their effectiveness to protect against corrosion.