Use of copper carbonate as corrosion inhibitor for carbon steel in post combustion carbon capture

The realisation of post-combustion CO ₂ capture (PCCC) at industrial scale remains limited; one challenge is the concerns around capital costs and another concern is corrosion of the system itself. Corrosion resistance and mitigation against the amine solvent monoethanolamine (MEA) was studied, using the inhibitor copper (II) carbonate basic (CC). Carbon steel (C1018) was tested in CO ₂ loaded, 5M aqueous MEA solution, alone and in the presence of CC, to assess the corrosivity of the solution. Immersion testing used mass loss, Fe and Cu ion concentration in solution via ICP-MS, imaging (SEM) and analytical techniques (XRD and EDX) to investigate the effect of corrosion. Generally, the use of CC improved C1018 corrosion resistance relative to C1018 alone. Even at low concentrations (0.9 mM), CC was effective in inhibiting corrosion against CO ₂ loaded MEA, as the observed corrosion rate was effectively zero and no dissolved Fe was detected in solution. There was no evidence of copper surface adsorption. To clarify the solution chemistry resulting in corrosion inhibition, the local chemical environment of Fe and Cu were probed by Cu and Fe K-edge X-ray Absorption Spectroscopy, respectively. The Cu K- edge HERFD-XANES spectra reveal that a Cu ²⁺ amine complex forms, critical to understanding the structure which is promoting significant corrosion inhibition.