Highly effective inhibition of mild steel corrosion in 3.5% NaCl solution by green Nettle leaves extract and synergistic effect of eco-friendly cerium nitrate additive: Experimental, MD simulation and QM investigations

The synergistic effects of eco-friendly cerium nitrate additive on the corrosion inhibition performance of green Nettle leaves extract were investigated on mild steel in 3.5% NaCl solution by electrochemical, surface characterization and theoretical molecular dynamics (MD) simulations and quantum mechanics (QM) methods. The effect of Nettle leaves extract: cerium nitrate ratio on the mild steel corrosion inhibition was studied. The electrochemical impedance spectroscopy (EIS) and polarization tests were applied to examine the corrosion inhibition properties. In addition, the adsorption process and the synergistic effects between Nettle leaves extract and cerium cations were theoretically evaluated by using MD simulations and QM computations based on density functional theory (DFT) approach. Surface characterization techniques namely field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were employed for studying the surface morphology and composition of the film deposited. The experimental results revealed that combination of Nettle leaves extract and cerium nitrate with ratio of 400 ppm:400 ppm resulted in the highest corrosion inhibition efficiency (about 95%) and a thick and nanostructure organic/inorganic film formation on mild steel based on the organic compounds of Nettle leaves extract, i.e., hystamine, serotonin and quercetin, and the cerium cations, namely histamine-Ce3+, serotonin-Ce3+ and quercetin-Ce3+. The mixture of Nettle leaves extract and cerium cations acted as a mixed type inhibitor with dominant effect on the anodic reactions restriction. Furthermore, the computational results obtained from MD simulations demonstrated the adsorption ability of organic-inorganic inhibitors onto steel substrate, implying their inhibition effects in agreement with experimental observations.