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The present study was devoted to the investigation of the effect of NO2 and OH group in the structure of two imidazopyridine, namely: (E)-N-(7-methyl-2-phenylimidazo[1,2-a]pyridin-3-yl)-1-(4-nitrophenyl)methanimine (Imid1) and (E)-4-(((7-methyl-2-phenylimidazo[1,2-a]pyridin-3-yl)imino)methyl)phenol (Imid2) on the corrosion inhibition efficiency of steel in acidic medium, to remediate mild steel in hydrochloric acid. The evaluation of this activity was revealed using several experimental techniques such as: weight loss measurements (WL), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS), UV-visible spectroscopy study, surface characterization by SEM, as well as the impact of temperature and concentration on the inhibition efficiency for two inhibitors. The results obtained from these techniques show that the inhibition efficiency is reduced by the effect of the nitro electron withdrawing group (NO2) in the Imid1 molecule, but increased by the presence of the donor group (-OH) in the Imid2 molecule. The comparison of the results obtained by UV-visible spectroscopy of the inhibited and uninhibited electrolyte provided evidence for the formation of an Fe-ligand complex of two imidazopyridine molecules in 1M HCl. Surface morphological studies by SEM revealed a uniform surface in the presence of the imid1 − 2 in contrast a destroyed surface in the absence of the inhibitors. Finally the results of DFT and MDS simulations are in good order with the experimental data and showed that the obtained order of the inhibition efficiency is always respected (Imid2 > Imid1).

In the pickling industry, corrosion can deteriorate the quality of equipment and supplies, causing financial losses and safety threats. Therefore, it has become crucial to develop novel corrosion inhibitors that are bioactive, efficient, affordable, medium-acid soluble, and ecologically safe to protect mild steel during industrial cleaning. In this work, three newly synthesized imidazo[1,2-a]pyridine derivatives were characterized by various spectroscopic techniques. The studied compounds were evaluated as corrosion inhibitors for mild steel in 1 M HCl medium using weight-loss, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. The imidazopyridine derivatives showed excellent anticorrosion performance, their inhibitory efficiencies increased with the increase of inhibitors concentration and evolved in the following order: Imd2 (98.1%) >Imd1 (96.5%) >Imd3 (95.3%). This order was justified by the presence of two chlorine atoms in the ortho position of the Imd2 structure. The three Imd derivatives obeyed to the Langmuir isotherm, this explained the formation of an organic monolayer on the steel surface indicated by the scanning electron microscope (SEM) and the atomic force microscope (AFM). In addition, density functional theory (DFT) and molecular dynamics (MD) simulations were performed to reveal the anticorrosion mechanism. The present study illustrates at the microscopic level how mild steel resists corrosion and ensures the safety of pickling.

In this modest work, a local biopolymer (CHA), biodegradable, non-toxic, and soluble in acidic media, was extracted from the plant Artemisia herba-alba located in the eastern region of Morocco, and characterized by FT-IR, in order to valorize it as a corrosion inhibitor of mild steel in 1 M HCl medium. The electrochemical tests show that the extract is an excellent corrosion protective agent, reaching a maximum value of 96.17% at the concentration of 800 mg/L in the inhibitor. The potentiodynamic polarization (PDP) curves indicate the mixed behavior of the extract, to reduce the current density from 3.445 mA/cm2 to 0.104 mA/cm2 in the presence of 800 mg/L in the inhibitor. The biopolymer CHA of the extract of Artemisia herba-alba undergoes the Langmuir adsorption isotherm, whose adsorption energy is −20.75 kJ/mol, which is attributed to the presence of electrostatic and covalent bonds. In addition, the visualization of the metal surface by a scanning electron microscope (SEM) indicates the formation of a protective layer formed by the extracts of Artemisia herba-alba, which confirms the protective characteristic of the extract used. Theoretical investigations by DFT, MD, and MC confirm previous experimental results.