CO2 loading-dependent corrosion of carbon steel and formation of corrosion products in anoxic 30 wt.% monoethanolamine-based solutions

• Initial corrosion of carbon steel was accelerated with increasing CO2 loadings.
• Formation of chukanovite and siderite was promoted with increasing CO2 loadings.
• The prior formed chukanovite was metastable and apt to transform into siderite.
• Protection of the formed layer was CO2 loading-, temperature- and O2-dependent.
• A couple of strategies were proposed to mitigate corrosion in CO2 capture process.

Corrosion of A106 carbon steel in anoxic CO2-loaded 30 wt.% monoethanolamine-based solutions (a corrosive solvent for post-combustion CO2 capture) with CO2 loadings ranging from 0.24 to 0.53 mol CO2/mol amine is investigated. The results show that corrosion and formation of a protective layer of corrosion products on the A106 surface are strongly CO2 loading-dependent. That is, initial corrosion is accelerated with increased CO2 loading. However, the formation of chukanovite and subsequently siderite, which dramatically inhibits the corrosion, was promoted with increasing CO2 loading. Chukanovite is a metastable intermediate corrosion product which transforms into siderite. Possible mechanisms are discussed.