Screening of Two Sulphur-Containing Schiff’s Bases Corrosion Inhibition Properties on CS: Gravimetric, Electrochemical and Quantum Chemical Studies

Novel sulphur (S)-containing Schiff’s bases, N-((1H-indol-3-yl)methylene)thiazol-2-amine (I3A2AT) and(13E)-N1,N2-bis((thiophene-2-yl)methylene) cyclohexane-1,2-diamine (T2CDACH), were synthesized. The structures were deep-rooted by mass, UV-visible, Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses. The ligands inhibition efficiency (  w%) on carbon steel (CS) corrosion in 1 M hydrochloric acid ( HCl) was studied using gravimetric analysis, electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation (PDP), electrochemical noise (ECN), quantum chemical and surface studies. Both Schiff’s bases acted as excellent inhibitors on CS corrosion in 1 M HCl. The excellent inhibitors performance was confirmed by the formation of protective adsorption films onto the CS surface. The inhibitors adsorption onto the CS surface followed Langmuir’s adsorption isotherm. Energies of the highest and lowest occupied molecular orbitals (E HOMO and E LUMO) , number of electrons transferred (∆N), electronegativity, chemical hardness, and so forth, were evaluated by quantum chemical studies. An acceptable correlation was observed between the results of quantum chemical calculations and other corrosion monitoring techniques. corrosion inhibitors.