Corrosion Resistance of Two Newly Synthesized 8-Quinolinol-Benzimidazoles on Carbon Steel: An Experimental and Theoretical Investigation

The newly designed 8-quinolinol-benzimidazoles, 5-(5-nitrobenzimidazol-2-yl)8-quinolinol (NBLQ) and 5-(5-methylbenzimidazol-2-yl)8-quinolinol (MBLQ), were explored for the protection of carbon steel (C-S) in hydrochloric acid electrolyte (1 M HCl) at 303 K using electrochemical, surface analysis techniques, and computational approaches. The findings exhibited that the examined 8-quinolinols have remarkable inhibiting characteristics, with their inhibition performances reaching a maximum of 96.6% for NBLQ and 93.9% for MBLQ at a concentration of 10-3M, respectively. Polarization study revealed that the 8-quinolinols acts as mixed-type inhibitors. NBLQ and MBLQ preserved the metal from the corrosive electrolyte by getting adsorbed on the C-S surface following the Langmuir isotherm adsorption model. Thermodynamic variables were assessed for activation and adsorption processes. The C-S surface morphology was investigated using scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy (SEM-EDS), which confirmed the formation of a protective thin film on the metal surface. The experimental findings are supported by computational correlations (density functional theory (DFT) and molecular dynamics (MD) simulations). Furthermore, the Fukui function and local softness indices were calculated to identify the most likely nucleophilic and electrophilic attack sites.