Corrosion Behavior of Carbon Steel in Diethylenetriamine Solution for Post-combustion CO₂ Capture

In the realm of postcombustion carbon capture, diethylenetriamine (DETA), recognized for its substantial CO₂ absorption capacity, presents a formidable challenge due to its corrosive impact on equipment. This study delves into the corrosion behavior of 20# carbon steel immersed in DETA solutions under varying conditions, employing weight loss and electrochemical methods. The investigation incorporates scanning electron microscopy/energy-dispersive spectroscopy and X-ray diffraction analyses for characterization. Corrosion experiments were also conducted in monoethanolamine (MEA) solutions for a comparative analysis. Results from the corrosion tests in DETA solutions mirror the temperature-dependent corrosion rate (CR) observed in MEA. However, a distinctive trend emerges as the CO₂ loading of DETA increases from 0.2 mol CO₂/mol amine to 1.2 mol CO₂/mol amine, leading to a continuous decrease in the CR of carbon steel-contrary to MEA solutions. This anomaly is attributed to DETA's robust complexing ability with metal ions and its elevated solubility of Fe²⁺ in solution. Additionally, an examination of the corrosion mechanism in the presence of oxygen was conducted through characterizing the specimen surface and solution precipitates postexperiment. The absence of a protective FeCO₃ layer can be attributed to insufficient concentrations of free Fe²⁺ and CO₃^2- in the solution, failing to achieve the minimum saturation required for protective film formation. The insights gained from studying the corrosion behavior of carbon steel in DETA solutions lay the groundwork for subsequent developments in corrosion inhibitors.