Synthesis, experimental, and computational studies of water soluble anthranilic organoselenium compounds as safe corrosion inhibitors for J55 pipeline steel in acidic oilfield formation water

Herein, we report the synthesis and corrosion protection properties of two water-soluble anthranilic acid-based organoselenium compounds, namely, sodium 2-amino-5-selenocyanatobenzoate (AnSe) and sodium 5,5′-diselanediylbis(2-aminobenzoate) (AnSe-SeAn). The inhibition behavior of AnSe and AnSe-SeAn for the corrosion of J55 steel in simulated acidic oilfield formation water at 50 °C was assessed using weight loss, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and surface morphology measurements. The diselenide-based anthranilic acid AnSe-SeAn manifested higher protection capacity (96.8%) than the selenocyanate analog AnSe (92.4%). The protective efficacy was enhanced in a concentration-dependent manner (up to 98.2% using 2.0 × 10⁻³ M of AnSe-SeAn at 50 °C). PDP plots indicated that AnSe and AnSe-SeAn were mixed-type inhibitors. The organoselenium molecules were adsorbed on the J55 steel surface and follow the Langmuir isotherm model via both physisorption and chemisorption. Surface morphology inspections via FTIR, FE-SEM/EDX, and XPS analysis affirmed the improvement of a protecting film that shields the J55 steel surface from corrosion at the optimal dose. Furthermore, computational studies via DFT and MC simulations were performed to discover the active sites on AnSe and AnSe-SeAn molecules responsible for the adsorption and protect the J55 steel surface. The current paper delivers very important findings in designing and preparation novel water-soluble anthranilic organoselenium inhibitors with high inhibition efficiency.