Alkaline ethanolamine as dual-functional agent: Effective CO2 capture agent and corrosion inhibitor for structural applications

Abstract

Continuous CO₂ emissions from automobiles and industrial sources pose significant environmental challenges. Concrete absorbs CO₂ from the atmosphere which accelerates corrosion of rebar. The objective of this study is to propose a revolutionary technique to use 2-(methylamino)ethanol (MAE) and N-Methyldiethanolamine (MDEA) as dual-functional agents for CO₂ absorption and corrosion inhibition. This study investigates the effect of MAE and MDEA on the carbonation of a simulated concrete pore solution (saturated Ca(OH)₂ solution containing NaCl) and simultaneously analyses the changes in microstructure, composition, and electrochemical properties of the steel exposed. Results showed that the presence of 5–10 mass% of MAE and MDEA in solution effectively absorbs CO₂, stabilizing pH between 8 and 9. XRF analysis showed that adsorbed Ca on steel was decreased from 30 mass% to 1 mass% due to the presence of 0.1 mol/dm⁻³(−|-) NaCl in a saturated Ca(OH)₂ (S1C) solution. Electrochemical test results showed that 10 mass % of MAE and MDEA addition in S1C exhibited an outstanding inhibition performance with 99.5 % inhibition efficiency. The excellent polarization resistance of steel with a low i_corr value of 70nA cm⁻² was observed in a carbonated SIC solution containing 10 mass % of MAE. Furthermore, local electrochemical measurements using a newly designed flow-type droplet cell showed that 10 mass% MAE is an effective inhibitor at welded zones. These findings highlight MAE as a promising candidate for corrosion inhibition of rebar in carbonated Ca(OH)₂ solution, suggesting valuable applications in enhancing the safety of critical infrastructures.