Corrosion Inhibition of Q235 Steel by a Novel Imidazoline Compound under H2S and CO2 Coexistence

We synthesized a new imidazoline compound, 1-(2-amido-thioureaethyl)-2-pentadecyl. imidazoline (IM-S). The corrosion inhibition performance and adsorption behavior for mild steel corrosion under H2S and CO2 coexistence were investigated by weight loss method, polarization curve, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The results indicated that IM-S had excellent corrosion inhibition performance, and both cathodic and anodic processes of mild steel corrosion were suppressed. The highest inhibition efficiency was 92.74%. We found that the adsorption of IM-S on mild steel could be fitted to a Langmuir isotherm equation, and it belonged to a mix. type adsorption, which was mainly dominated by chemisorption. The relationship between the molecular structure of IM-S and the inhibition efficiency was investigated using quantum chemical calculations.