4-Ferrocenylbutyl-based corrosion inhibitors for mild steel in acidic solution

Abstract

The weak corrosion resistance of mild steel (MS) is considered a severe problem in many industrial applications. The application of corrosion inhibitors is suggested to mitigate the corrosion of steel. Within this framework, a series of novel inhibitors, including 4-ferrocenylbutyl formate, 4-ferrocenylbutyl acrylate, and 4-ferrocenylbutyl phenylacetate, was synthesized and subsequently characterized using 1H NMR, 13C NMR, and FT-IR spectroscopies. The corrosion inhibition properties of synthesized components were evaluated for MS in 1 M HCl solution through electrochemical impedance spectroscopy (EIS), Tafel, Atomic force microscopy (AFM), and scanning electron microscopy (SEM). SEM images showed the presence of a protective layer on the steel surface in the presence of inhibitors. This thick layer, visible to the naked eye, is responsible for a significant resistance against corrosion. EIS data indicated that the inhibition efficiency of 4-ferrocenylbutyl formate (C) increased from 92% to 94% after 14 days of immersion in 1 M HCl. Furthermore, the results show that the Rct of inhibited MS after 2 h increased from 57 to 880 Ω cm2 in 4 mM C inhibitor, and it enhanced to 1870 Ω cm2 after 170 h toward the uninhibited surface. Proposed inhibitors have extraordinary adsorption abilities on the metal surface to increase corrosion protection, improving this adsorption over time. Besides, the potentiodynamic polarization results disclosed that steel corrosion protection after two weeks of immersion in the acidic solution containing (C) inhibitor was about 20 times higher than the inhibitor-free solution. Synthesized ferrocenylbutyl derivatives can be utilized for prolonged corrosion inhibition purposes. Furthermore, density functional theory calculations revealed a linear correlation between the adsorption energies and charge-transfer values of studied 4-ferrocenylbutyl derivated and their inhibition capacity.