Corrosion behaviour of mild steel in 1-alkyl-3-methylimidazolium tricyanomethanide ionic liquids for CO2 capture applications

Abstract

The corrosion behaviour of mild steel (MS) was systematically investigated as a function of the alkyl chain length in the cation of 1-alkyl-3-methylimidazolium tricyanomethanide ([C n mim]TCM, n ¼ 2, 4, 6 and 8) ionic liquids (ILs) with respect to their potential application as a structural material and solvents for CO 2 capture plants respectively. The surface of MS was examined by scanning electron microscopy, energy dispersive X-ray spectroscopy and micro-Raman mapping before and after immersion testing at temperatures of 70 and 80 C for durations varying from 1 hour to 10 days. Corrosion initiates at the sites of MnS inclusions on the surface of MS, resulting in the formation of cavities due to the MnS dissolution, which may be surrounded by corrosion products containing magnetite (Fe 3 O 4 ) and maghemite (g-Fe 2 O 3 ). The amount of the corrosion products generated around the inclusion sites decreased with the increase of the cation alkyl chain length, following the order [C 2 mim]TCM > [C 4 mim] TCM > [C 6 mim]TCM z [C 8 mim]TCM. This was attributed to the corrosion inhibition effect of the ILs through adsorption on the metal surface and blocking active sites, with the inhibition efficiencyincreasing with the alkyl chain length. The underlying mechanism was associated with corrosion processes at active sites on the MS surface, such as sulphide inclusions, in the presence of residual water and oxygen in the IL. It was shown that increase of the water content in the ILs to about 50 000 ppm resulted in faster dissolution of the MnS inclusions. Finally, it was demonstrated that removal of oxygen from the IL significantly reduced the corrosion rate.

Microscopic study of the corrosion behaviour of mild steel in ionic liquids for CO2 capture applications

“…As discussed previously, 16 1 day immersion at 80 C is sufficient for complete dissolution of the MnS inclusions. Thus, the amount of Mn 2+ transferred to the liquid phase does not change signicantly with increase of immersion time to 30 days as conrmed by weight monitoring.…”

“…8,16 Sodium molybdate Na 2 MoO 4 $2H 2 O ($99.0% purity, Sigma-Aldrich) was used to study its inhibition effect with [BHC]BTA. 8,16 Sodium molybdate Na 2 MoO 4 $2H 2 O ($99.0% purity, Sigma-Aldrich) was used to study its inhibition effect with [BHC]BTA.…”

CO2 Capture Efficiency, Corrosion Properties, and Ecotoxicity Evaluation of Amine Solutions Involving Newly Synthesized Ionic Liquids

“…Because of the low cost, the use of MS might be the preferable choice for building CO 2 capture installations provided that the corrosion processes could be effectively alleviated. In a previous study by the authors, 9 Finally, the ecotoxicity of the tested solvent formulations was evaluated by monitoring the culture growth of the green algae Chlamydomonas reinhardtii in terms of chlorophyll concentration. While ILs pose little threat of airborne toxicity, they would likely enter aquatic ecosystems in the case of an accidental release, and because many of them are water-soluble, they are likely to transport readily through the environment and contact the biota.…”

Neutron Reflectometry for Studying Corrosion and Corrosion Inhibition

“…This critical finding is believed to arise from the presence of 'active sites' at the metal surface that are particularly prone to corrosion and hence nucleate dissolution of the metal. By binding specifically to these active sites, the surface is effectively passivated [98,99]. Another example of combining NR and electrochemical measurements is found in the work of Saville et al They collected data on a short timescale to monitor ion and solvent trapping within a nickel hydroxide film as the potential was cycled and saw a hysteresis of reflectivity as the film was oxidised and reduced.…”

“…This critical finding is believed to arise from the presence of 'active sites' at the metal surface that are particularly prone to corrosion and hence nucleate dissolution of the metal. By binding specifically to these active sites, the surface is effectively passivated [98,99].…”