Inhibitive Mechanism of Acid Corrosion of Cold-Rolled Steel by Polyethylene Glycol via Experimental, Computational and Surface Analytical Approaches

Corrosion inhibition effect of aqueous polyethylene glycol (PEG) on cold-rolled steel corrosion in 1.0 M HCl solution was studied using weight loss, electrochemical potentiodynamic polarization, quantum chemical computation, molecular dynamics simulation, and scanning electron microscopy (SEM) analytical techniques. The effect of immersion time, inhibitor concentration and temperature on the corrosion behaviour of cold-rolled steel in 1.0 M HCl was studied. The results revealed that PEG satisfactorily inhibited corrosion of cold-rolled steel in the acid solution by adsorption of its molecules on the metal surface, decreasing both the anodic and cathodic reactions. Temperature studies showed that inhibition efficiency increased with rise in temperature from 303 – 343 K. Quantum chemical calculations conducted using density functional theory (DFT) showed values of E HOMO , E LUMO and energy gap for PEG to be − 7.2219 eV, − 0.3958 eV and 6.8261 eV, respectively, and thus confirmed the interaction between the PEG inhibitor molecules and the metal surface. Furthermore, the computed values of Fukui indices indicated that O(7) atom in the PEG molecule was most susceptible to nucleophilic attacks, while the O(10) atom was well disposed for electrophilic reactions. The negative values of interaction energy obtained by molecular dynamics simulation, -107.7898 kcal/mol and -109.5136 kcal/mol at 303 K and 343 K, respectively, confirmed that PEG-metal interaction was good. SEM was used to confirm the adsorption of PEG on the surface of cold-rolled steel. Based on the analyses conducted, the inhibitive mechanism for corrosion of cold-rolled steel in 1.0 M HCl solution has been established.