Enhanced the protection capacity of poly(o-toluidine) by synergism with zinc or lanthanum additives at C-steel/HCl interface: A combined DFT, molecular dynamic simulations and experimental methods

In this paper, poly(o-toluidine) (POT) is a prepared by situ chemical oxidative polymerization method. The structural configuration of the as-prepared POT is confirmed by Fourier-transform infrared spectroscopy (FT-IR), UV–vis spectroscopy, X-Ray Diffraction (XRD), Transmission electron microscopy (TEM), Field emission scanning electron microscope (FE-SEM) analyses. The inhibition action of POT alone and in the presence of Zn2+ or La3+ additives at C-steel/1.0 M HCl solution surface is examined using linear polarization resistance (LPR) corrosion rate, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) measurements at various temperatures (30–60 °C). The POT prevents the C-steel from corrosion up to 82.8%. The addition of Zn2+ or La3+ cations to POT is found to synergistically improve the corrosion protection capability of POT with a capacity of ~96.8 and 98.9%, respectively. Temperature–protection capacity relation indicates the physisorption of POT onto a metal surface and chemical adsorption when POT was incorporated with Zn2+ or La3+ additives. PDP findings displayed that POT alone and POT + Zn2+ or La3+ systems behaved as inhibitors of mixed-type. The adsorption of POT onto the C-steel interface followed the Langmuir isotherm model. FTIR, XRD and FE-SEM/EDX are applied to investigate the surface morphology. The outcomes of molecular dynamic (MD) simulations and density functional theory (DFT) calculations indicate elevated adsorption probability of neutral POT than protonated form. [Display omitted] •POT was prepared and specified in terms of XRD, UV–vis spectra, FTIR, FESEM, and HRTEM.•The inhibition action of individual POT and in combination with Zn2+ or La3+ additives is investigated.•XRD, FTIR and FE-SEM/EDX studies established the formation of a protective film on the steel interface.•PDP outcomes showed that the investigated inhibitor systems behaved as mixed-type inhibitors.•MD simulations and DFT calculations indicate high adsorption probability of neutral POT than protonated form.