Density Functional Theory Studies on New Possible Biobased Gemini Corrosion Inhibitors Derived from Fatty Hydrazide Derivatives

Several new possible biobased corrosion inhibitors derived from fatty hydrazide derivatives were analyzed using quantum chemical calculations via the density functional theory method to investigate the chemical reactivity and inhibition efficiencies against corrosion in metal steel. The study confirmed that the fatty hydrazides showed significant inhibitive performances based on their electronic properties, revealing band gap energies of 5.20 to 7.61 eV between the HOMO and LUMO. These energy differences decreased from 4.40 to 7.20 eV when combined with substituents of varying chemical compositions, structures, and functional groups, associated with higher inhibition efficiency. The most promising fatty hydrazide derivatives are terephthalic acid dihydrazide combined with a long-chain alkyl chain, which resulted in the lowest energy difference of 4.40 eV. Further inspection showed that the fatty hydrazide derivatives' inhibitive performances increased with increasing carbon chain length [from 4 (4-s-4) to 6 (6-s-6)], with a concomitant increase and decrease in hydroxyl and carbonyl groups, respectively. Fatty hydrazide derivatives containing aromatic rings also showed increased inhibition efficiencies following their contribution to improve the compounds' binding ability and adsorption on the metal surface. Overall, all data were consistent with previously reported findings, envisaging the potential of fatty hydrazide derivatives as effective corrosion inhibitors.