A combined electrochemical and DFT investigation of ornidazole as a benign anti-corrosion agent for carbon steel materials in acidizing environments

The corrosion inhibition performance of ornidazole was investigated as an eco-friendly option during the acid cleaning of carbon steel using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in combination with density functional theory (DFT) simulations. The inhibition efficiency was noted to rise with a rise in ornidazole concentration and exposure time. The maximum inhibition efficiency after 0, 1 and 7 days were attained at 1.6 g/L with values of 93.8, 96.2 and 98.7 %, respectively. Potentiodynamic polarization revealed that indazole is a mixed-type corrosion inhibitor. EIS indicates and increase in corrosion resistance with ornidazole concentration. SEM/EDX were consistent with the electrochemical results and indicate that ornidazole inhibits steel corrosion by surface adsorption which was consistent with Langmuir adsorption isotherm (R² = 0.9999). The values of K_ads indicate that ornidazole is more strongly adsorbed with an increase in concentration of ornidazole. The values of ΔGads (−5.69 to −11.75 kJ/mol) indicate that the adsorption is spontaneous. The inhibitory properties were found to be related to the molecular properties indicated by theoretical insights from DFT simulations which revealed susceptible adsorption sites on the ornidazole molecules from the deduced quantum descriptors, natural population analysis, density of states and molecular electrostatic potential. The results herein indicate that ornidazole is a suitable corrosion retardant for carbon steel in acidic environments.