Experimental and Theoretical Investigations of the Inhibition of the Corrosion of Mild Steel in HCl by Synthesized Piperazin Derivatives

Abstract

In this study, two organic molecules namely, [4-(4-aminobenzoyl)-piperazin-1-yl)] furan-2-yl) methanone (4-4-ABPFM) and 4-(4-aminophenylpiperazin-1-yl) furan-2-yl) methanone (4-4-APPFM) were synthesized and characterized using FTIR, UV–visible, thin layer chromatography, C-13 and proton NMR. The corrosion inhibition efficiencies of these molecules were tested using weight loss, polarization and AC impedance methods. Quantum chemical calculations (which included local selectivity, global reactivity and Monte Carlo simulation) were also implemented to complement the experimental data. The results obtained provided information confirmed that the synthesized compound has some inherent corrosion inhibition potentials due to the presence of aromatic rings, pi-electron systems, heteroatoms and corrosion structure parameters. The maximum inhibition efficiencies were 95 and 91% for 4,4-ABPFM and 4,4-APPFM respectively. The ideal fitness of the Langmuir isotherm with slope and R² values approximating unity was also upheld. Theoretical calculation results showed strong accord to experimental values and supported higher efficiency for 4,4-ABPFM than 4,4-APPFM. Monte Carlo simulation showed that the adsorption energy is negative and also supported evidence drawn from the experiment, which is the spontaneous adsorption of the inhibitors on the metal surface.