Detailed atomic/molecular-level/electronic-scale computer modeling and electrochemical explorations of the adsorption and anti-corrosion effectiveness of the green nitrogen-based phytochemicals on the mild steel surface in the saline solution

High corrosion protection performance and eco-friendly properties have made the plants' extracts as effective corrosion inhibitors for mild steel in chloride-containing media. The presence of nitrogen-based functionalities in the Popover somniferum leaves/stem molecules made it a high-efficient corrosion inhibitor in simulated seawater. The adsorption of graphene-like molecules of Popover sominiferum on the substrate was studied theoretically (by molecular dynamic (MD), Monte Carlo (MC), and density functional theory (DFT)) and experimentally by taking the advantages of Fourier transform infrared spectroscopy (FT-IR), grazing incidence X-ray diffraction (GI-XRD), Raman spectroscopy, ultraviolet-visible (UV-Vis) test, atomic force microscope (AFM), field emission scanning electron microscope (FE-SEM), and contact angle (CA) method. Moreover, the corrosion inhibition degrees and mechanism of the Popover sominiferum extract (PSE) in different concentrations were examined through the potentiodynamic polarization spectroscopy (PPS) and electrochemical impedance spectroscopy (EIS). EIS outcomes evidenced that by addition of 1600 ppm of PSE to the 35% wt. NaCl media, an inhibition efficiency (IE) of 91%, was achieved. In particular, the Nyquist diagram illustrated that the system resistance reached approximately 15 k Omega.cm(2) in the case of the PSE1600 sample. The FE-SEM images and Raman spectroscopy results affirmed the steel surface coverage by an inhibitive graphene-like film. Actually, the construction of some complexes such as p-tert-Pentyl-N,N-bis(3-phenylpropyl)aniline, and iron cyanide was reported by GI-XRD analysis. Additionally, the PSE molecules adsorption on the mild steel surface was also proved by the comprehensive theoretical studies. (C) 2020 Elsevier B.V. All rights reserved.