Experimental and Computational Study of Ecofriendly Synthesize d Imine Cationic Surfactants as Corrosion Inhibitors for Carbon Steel in 1 M HCl

Abstract Most research interests focused on the development of non-toxic and environmentally green corrosion inhibitors. In this work, three environment friendly corrosion inhibitors based on cinnamaldehyde named N,N-dimethyl-N-(2-((3-phenylallylidene) amino)ethyl)octan-1-aminiumbromide (PhAEO), N,N-dimethyl-N-(2-((3-phenyl allylidene) amino)ethyl)decan-1-aminiumbromide (PhAED) and N,N-dimethyl-N-(2- ((3-phenylallylidene)amino)ethyl)dodecan-1-aminiumbromide (PhAEDD) were prepared. The chemical structures of the prepared green corrosion inhibitors were confirmed by FTIR and 1 H-NMR. Their surface activities were studied using different surface parameters. The corrosi on inhibition efficiency of these compounds in 1 M hydrochloric acid on carbon steel was investigated chemically using weight loss method at varing temperatures (30, 45, and 60°C) and electrochemically at 30°C using potentiodynamic polarization measurements and electrochemical impedance spectroscopy. The carbon steel surface was characte rized by Scanning Electron Microscopy. The results show that the prepared compounds have a significant inhibiting effect on the corrosion of carbon steel and protection efficiencies up to 92%. These results were supported by theoretical studies using Density Functional Theory (DFT), which was used to calculate some quantum chemical descriptors, particularly the energy of Highest Occupied Molecular Orbital (E HOMO ), Lowest Unoccupied Molecular Orbital (E LUMO ) and the energy band gap ΔE gap . Fukui indices f + and f – for local nucleophilic and electrophilic attacks were considered. The theoretical results show that the behavior of the energy gap and adsorption energy is consistent with the sequence of the percent inhibition efficiency obtained by chemical and electrochemical measurements.