Effect of the addition of two pyrazole derivatives on behavior of the corrosion of mild steel in a 1 M HCl medium using experimental and theoretical insights

In this paper a comparative experimental and theoretical study of the inhibition capacity of two pyrazolic compounds, namely; Pyz1: N-(1H-pyrazol-1-yl)methyl)-5-bromopyridin-2-amine and Pyz2: ((1H-pyrazol-1-yl)methylamino) benzoic acid, against the corrosion of carbon steel was carried out in an acidic medium (1 M HCl at 30 degrees C) according to different weight loss and electrochemical methods (potentiodynamic and electrochemical impedance spectroscopy, EIS). The analysis of the experimental results obtained revealed that Pyz1 is the most effective inhibitor, even at low concentrations and that its inhibition efficiency increased with the concentration of the inhibitor. The data obtained from the AC impedance measurements were analyzed to model the corrosion inhibition process using appropriate equivalent circuit models. The adsorption of these inhibitors on the carbon steel surface in acidic medium followed the Langmuir adsorption isotherm. The calculated Delta G(ads)(0) values indicate that these compounds are chemisorbed on the metal surface. Through a theoretical study, using the density functional theory (DFT) method, we demonstrated the existence of a correlation between molecular structure and their inhibitory power.