Green synthesis, electrochemical, DFT studies and MD simulation of novel synthesized thiourea derivatives on carbon steel corrosion inhibition in 1.0 M HCl

Abstract

The corrosion inhibiting effect of four new synthesized thiourea derivatives compounds, their structures were identified based on spectral data 1H NMR and FTIR spectra, namely N-((2-aminoethyl)carbamo-thioyl)propionamide (ACP), N-(bis(2-hydroxyethyl)carbamothioyl) propionamide (BCP), N-((2-hydroxy-ethyl)carbamothioyl)propionamide (HCP) and N-((2-((2-((2-((2-aminoethyl)amino)ethyl)amino)ethyl)amino)ethyl)carbamothioyl)propionamide (ECP) as nontoxic corrosion inhibitors for carbon steel in 1.0 M HCl solutions, was evaluated by experimental and theoretical studies. The results of electrochemical frequency modulation, EFM, electrochemical impedance spectroscopy, EIS, and potentiodynamic polarization, PDP at inhibitors concentrations (10−6-10−2M) showed that, the inhibitory efficient of the prepared compounds improves with an increase in their concentrations and the corrosion inhibition performance of ECP was much higher than that of ACP, BCP and HCP. The Langmuir adsorption isotherm model indicated spontaneous adsorption of thiourea derivatives on the carbon steel surface and morphological surface analysis like scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) indicated that inhibitors molecules adhere and construct a stronger protective layer on the steel surface. Quantum chemical calculation, Natural Bonding Orbital (NBO) analysis, Molecular Dynamic Simulation (MD) and Radial Distribution Function (RDF) were in perfect agreement with each other suggesting synthesized thiourea derivatives to be environmental friendly corrosion inhibitors.