Outstanding anti-corrosion performance of two pyrazole derivatives on carbon steel in acidic medium: Experimental and quantum-chemical examinations

Corrosion inhibition performance of two pyrazole derivatives, namely N-((1H-pyrazol-1-yl)methyl)pyrimidin-2-amine (PPA), 2-(((1H-pyrazol-1-yl)methyl)amino)benzoic acid (PMB), carbon steel (CS) was assessed in 1 M HCl medium by means of electrochemical impedance spectroscopy (EIS), weight loss, potentiodynamic polarization measurements (PDP), Uv–visible spectroscopy, and scanning electron microscopy with energy dispersive X-ray (SEM- EDX), as well as molecular modeling techniques. Results indicated that the inhibition efficiencies increased with the concentration of inhibitor, but decreased proportionally with temperature to reach a maximum of 94 % for PPA and 92 % for PMB at 10−3 M and 303 K, respectively, whereas it was 76.9 and 72.3 %, respectively, at 10−3M and 333 K. PDP plots reveal the anodic-type behavior of PPA while the mixed-type behavior of PMB. The EIS plots showed that charge transfer resistance increased and double-layer capacitance decreased with increasing the concentration of studied inhibitors due to the adsorption of inhibitor molecules on the CS surface. Moreover, the adsorption of pyrazole derivatives on the CS surface obeys the Langmuir adsorption isotherm and contains a chemisorption mechanism. Thermodynamic parameter magnitudes suggest that pyrazole derivatives were physiosorbed on the CS surface. SEM-EDX revealed the formation of an adsorption-related protective inhibitor film on the CS surface. Theoretical studies using density functional theory (DFT) for PPA and PMB molecules are performed in gas and aqueous phase conditions. The calculated data are in good agreement with the experimental results. Molecular Dynamic simulations (MDS) exhibit that the neutral and protonated forms of PPA and PMB adsorb on Fe (1 1 0) surface with a parallel mode.