Synthesis and evaluation of anticorrosive properties of cationic benzenesulphonamide surfactants on carbon steel under sweet conditions: Empirical and computational investigations

In this study, three cationic surfactants bearing a benzenesulphonamide moiety as corrosion inhibitors (PSA-8, PSA-10, PSA-12) were synthesized using a straightforward two-step process. Their chemical structures were investigated via spectroscopic tools such as ¹H and ¹³C NMR. The surface activity of as-prepared cationic surfactants was examined. To evaluate the effectiveness of these surfactants in the corrosion protection of carbon steel pipelines (C1018-steel) in a CO₂-3.5 % NaCl environment, several techniques were used, including electrochemical measurements (potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques), surface morphology examinations applying X-ray photoelectron spectroscopy (XPS) analysis, density functional theory (DFT) calculations, and Monte Carlo (MC) simulations. Notably, the corrosion efficiency of the PSA surfactants was compared with previously reported cationic surfactants containing the CN group (i.e., an electron-withdrawing group). The experimental results showed excellent inhibition performance of the PSA surfactants, with inhibition capacities ranging from 92.8 % to 97.0 %. This indicates that removing the CN group has significantly enhanced the corrosion inhibition efficiency, shedding light on the electronic effect as well as the adsorption and corrosion processes. Analysis of the Tafel data indicated that these surfactants functioned as mixed-type inhibitors and followed the Langmuir isotherm model in their adsorption on the carbon steel interface and the corrosive medium. XPS analysis confirmed the establishment of a shielding barrier at the interface of the carbon steel. DFT calculations were employed to establish the correlations between theoretical parameters and experimental observations, thereby validating their connection. Moreover, the employment of MC simulations validated the efficacy of the adsorption properties of the synthesized surfactants on the iron (1 1 0) surface. Ultimately, this investigation provides substantial insights into the development and formulation of bioactive inhibitors characterized by their potent inhibitory effectiveness.