Corrosion Inhibition of Carbon Steel C45 Using New Azo Derivative in HCl Solution: Synthesis, Potentiostatic Measurement, and DFT Studies

In this study, a new azo derivative, namely methyl-5-((2-chloro-4-((2-(diethylamino)ethyl)carbamoyl)-5-methoxyphenyl)diazenyl)-2-hydroxybenzoate, was successfully synthesized through a multistep process involving the diazotization of metoclopramide, the addition of methyl salicylate, and subsequent temperature and pH adjustments. The synthesis yielded azo compound with 90%, and its structure was characterized using FT-IR and 1H-NMR spectroscopy. The synthesized azo compound was then evaluated as a corrosion inhibitor for carbon steel C45 in 0.1 M HCl, employing potentiodynamic polarization technique (Tafel extrapolation) over a temperature range of 293 to 313 K. The corrosion inhibition efficiency exhibited a concentration-dependent increase, reaching 94% at 300 ppm inhibitor concentration at 293 K, accompanied by a shift in corrosion potential towards the negative direction, indicating the cathodic nature of the inhibitor. Thermodynamic analysis revealed the influence of temperature on the corrosion inhibition efficacy, demonstrating increased activation energy and endothermic dissolution of carbon steel. These observations were supported by the theoretical density functional theory (DFT) method at the B3LYP/6-311++G basis set for the inhibitor.