Electrochemical, morphological and theoretical evaluation of a new poly(3-sulfolene-co-cis-2-butene-1,4-dilinoleate) against corrosion of AISI 1020 steel in 0.1 N HCl solution

This research includes the preparation of a new poly(3-sulfolene-co-cis-2-butene-1,4-dilinoleate) (PSCOCBDL) by free radical polymerization of the preliminarily prepared cis-2-butene-1,4-dilinoleate with 3-sulfolene. This prepared copolymer was diagnosed using Fourier transform infrared spectroscopy and Gel permeation chromatography. The corrosion inhibition effect of poly(3-sulfolene-co-cis-2-butene-1,4-dilinoleate) on AISI 1020 steel corrosion in 0.1 N hydrochloric acid solution was studied at a temperature 298 K by means of electrochemical impedance spectroscopy and potentiodynamic polarization techniques. A set of experiments with different concentrations of the inhibitor copolymer (15, 30, 45 and 60 ppm) were conducted. The study revealed that the inhibition efficiency increases with an increase in concentration. Potentiodynamic polarization measurements detected that the PSCOCBDL copolymer was a corrosion inhibitor of anodic type. Atomic force microscopy technique was employed to determine the surface morphology of AISI 1020 steel samples after exposure both in uninhibited and inhibited medium. The morphological study indicated that adsorption of the corrosion inhibitor copolymer PSCOCBDL on AISI 1020 steel surface resulted in building a protective layer. The adsorption of the prepared copolymer on AISI 1020 steel surface obeys the Langmuir isotherm. Various quantum chemical descriptors have been calculated based on the density functional theory, such as E-HOMO, E-LUMO, Delta E, chi, eta, S, and mu, which are related most closely to the anti-corrosive features of the examined copolymer. A molecule with a higher E-HOMO can take electrons speedily from an appropriate acceptor molecule with a lower-energy vacuous molecular orbital, while the E-LUMO value indicates how well the molecule can hold back electrons.