Structural effect of bipyrazole derivatives on corrosion inhibition of carbon steel in 1 M HCl: weight loss, electrochemical measurements, XPS/SEM surface analysis, DFT and MC simulations

The inhibitory study of 4-(bis((1H-pyrazol-1-yl)methyl)amino)phenol (2PzH) and 4-(bis(3,5-dimethyl-1H-pyrazol-3-ylmethyl)amino)phenol (2PzMe) on carbon steel (CS) corrosion in 1 M HCl aggressive medium was conducted via weight loss measurement, electrochemical techniques, XPS and SEM analysis. The inhibition efficiency increases with the concentration of 2PzH, reaching 95.7%, and for 2PzMe, it reached 95.9% at 10−3 M and 303 K. Potentiodynamic polarization (PDP) measurements also argued that these compounds were mixed inhibitors. EIS diagrams showed that the corrosion process was mainly controlled by charge transfer, and the polarization resistance increased with the increase in inhibitor concentration. The bipyrazole compounds were chemisorbed on the steel surface, as stated by the Langmuir adsorption model. These results were further strengthened by elemental characterization of the metal/solution interface, employing XPS for both tested molecules. SEM analysis disclosed the formation of a passive film on the metallic surface. The computational approach was computed utilizing the DFT method and Monte Carlo/molecular dynamics (MC/MD) analysis in order to correlate the electron properties with the adsorption and inhibitory actions of both compounds. The theoretical results showed good agreement with the experimental results.