Corrosion inhibition of Q235 and X65 steels in CO2-saturated solution by 2-phenyl imidazoline

This study examined 2-phenyl imidazoline (2-PI) as an eco-friendly corrosion inhibitor for Q235 and X65 steels with various microstructures in CO2-saturated solution. The inhibition performances of the 2-PI inhibitor for both steels were comparatively studied through electrochemical tests, weight-loss method, wire beam electrode (WBE) technique as well as surface analysis. The results demonstrate that the 2-PI compound acts as a mixed-type inhibitor and exhibits effective and durable inhibition performance against general and localized corrosion. The adsorption of 2PI molecules on steel surfaces is exothermic, spontaneous and follows the Langmuir isotherm model. Furthermore, the steel microstructure strongly influences the adsorption behavior of 2-PI inhibitor, the Q235 steel with a higher pearlite/ferrite ratio promotes the physical adsorption of the protonated 2-PI molecules at lower concentrations, and the X65 steel with a lower pearlite/ferrite ratio enhances the chemical adsorption of the unprotonated 2-PI molecules at higher concentrations. Additionally, the adsorption mechanism was also discussed based on the evaluated thermodynamic data and the results of X-ray photoelectron spectroscopy (XPS) analysis. (c) 2023 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.