Corrosion inhibition efficiency and adsorption mechanism of two dihydropyridazin-3(2H)-ones on carbon steel in hydrochloric acid medium: Experimental verification and theoretical analysis

Two analogs of Dihydropyridazin-3(2H)-ones, namely (E)-5-(4-chlorobenzylidene)-6-methyl-4,5-dihydropyridazin-3(2H)-one (PZ1) and (E)-5-(4-methoxybenzylidene)-6-methyl-4,5-dihydropyridazin-3(2H)-one (PZ2) was evaluated as a corrosion inhibitor for carbon steel during acidizing through a combination of experimental techniques, including potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and solution and surface analysis using scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDS), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), contact angle measurements, UV–visible spectroscopy, and X-ray diffraction (XRD). Density Functional Theory (DFT) and molecular dynamics (MD) simulations are employed to clarify the inhibition mechanism of the two examined inhibitors. Dihydropyridazin-3(2H)-one analogs demonstrate superior inhibition of carbon steel acidizing, with their efficacy being contingent upon temperature and concentration, with a maximum of 97.4 % for PZ2 and 94.1 % for PZ1 at 0.001 M at 303 K. PDP results indicate that PZ2 and PZ1 have a mixed character with anodic preponderance. Furthermore, dihydropyridazin-3(2H)-one analogs were chemisorbed according to the Langmuir adsorption model, and the adsorbed layers of PZ1 and PZ2 molecules were analyzed using SEM-EDS, AFM, FT-IR, and contact angle measurements. The two theoretical techniques utilized offer precise explanations for the adsorption behavior of the two inhibitors under consideration.