Protectiveness and stability of iron carbonate films on carbon steel in mildly alkaline aqueous alkanolamine CO2 environments.

Carbon steel (CS) was pre-treated in CO 2 -saturated methyldiethanolamine (aq) to form FeCO 3 surface films, the protectiveness of which against corrosion in monoethanolamine was studied using electrochemical impedance spectroscopy, open circuit potential measurements and ex situ surface characterisation. Only pure, dense FeCO 3 films were found to provide protection in lab-scale tests. Dissolved O 2 in pre-treatment solutions resulted in traces of iron (hydr)oxide within the films, exacerbating non-uniform corrosion. Impure films were compromised in pilot-scale experiments in the CO 2 capture plant at Imperial College London. Therefore, pre-treating CS with methyldiethanolamine is not a robust corrosion control strategy for industrial CO 2 capture plants. • Pilot-scale stability tests of protective films formed through pre-treatment were conducted. • Pure FeCO 3 formed by pre-treating carbon steel was protective against corrosion in ethanolamine. • Dissolved O 2 in methyldiethanolamine resulted in iron oxide within the film. • Iron (hydr)oxide in surface films enhanced non-uniform corrosion in ethanolamine. • Pre-treatment with methyldiethanolamine should not be used for corrosion control. [ABSTRACT FROM AUTHOR]