Experimental evaluation and theoretical insights into substituted pyrazole as a high-performance corrosion inhibitor for carbon steel in acidic media

In the present work, we have synthesized and characterized a new pyrazole derivative ( E )-N′-(4-hydroxybenzylidene)-5-methyl-1H-pyrazole-3-carbohydrazide (PM) using various spectroscopic techniques. The electrochemical results (potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS)) showed that it was a very efficient inhibitor for carbon steel (CS) corrosion in 1 M HCl solution, achieving 95.6% inhibition efficiency at 10 −3 M and 303 K and retains 82.7% efficiency at 10 −6 M. Construction of a protective layer adsorbed on the steel surface was characterized by surface techniques, including scanning electron microscopy in conjunction with energy-dispersive X-ray analysis (SEM/EDX), atomic force microscopy (AFM), measurements of contact angle, X-ray diffraction (XRD), and UV–visible spectroscopy. The results, moreover, showed that the inhibitor obeys the Langmuir adsorption isotherm with ΔG ads = -45.25 kJ/mol, and it was found that upon adsorption, this inhibitor was mostly chemisorbed. PDP analysis has shown that PM behaves as a mixed-type inhibitor but with a predominant anodic mechanism. In addition, quantum chemical calculations and molecular dynamics simulations gave further insight into its electronic structure and adsorption behavior on the metal surface.