Synthesis and Kinetics of Corrosion Inhibition of Water-Soluble Terpolymer of Polyvinyl Alcohol Functionalized with Vinyl Sulfonate and p-Vinyl Benzene Sulfonate, in Molar HCl

Abstract

A water-soluble terpolymer polyvinyl alcohol-g-poly(vinyl sulfonate-p-vinyl benzene sulfonate) was synthesized by free radical polymerization of polyvinyl alcohol with monomers sodium salt of vinyl sulfonic acid and p-vinyl benzene sulfonic acid. The formation of terpolymer was confirmed using FTIR and 1H NMR spectra and the thermal properties of the terpolymer were confirmed using TGA and DSC. The performance of the water-soluble terpolymer inhibitor for corrosion of mild steel in 1 M HCl solution at varying temperatures was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy. Weight loss measurements showed that the inhibitory character within the studied environment increased with increasing concentration, but highest efficiency was obtained with rise in temperature. Polarization results revealed that the terpolymer inhibitor functions as a mixed-type inhibitor providing an absolute control on both cathodic and anodic reactions. Impedance studies showed that the inhibitor’s adsorption took place at the most active sites on the metal surface resulting in a homogenous surface. The inhibitive action of the terpolymer was explained in view of adsorption on the surface of steel. The surface coverage data were fitted to various adsorption isotherms and best-fit isotherm was selected for determination of thermodynamic parameters of adsorption. Supporting information pertaining to inhibitor adsorption on the metal surface was provided using surface imaging techniques like scanning electron microscopy and Atomic force microscope.