Inhibition of carbon steel corrosion in acidic solution using some newly polyester derivatives

Abstract

Two polyesters derivatives of maleic and phthalic anhydride with polyethylene glycol were synthesized and characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD). The efficiency of these compounds as corrosion inhibitors for carbon steel in 1M HCl, has been determined by gravimetric and electrochemical measurements. Surface morphologies scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) were used to characterize the steel surface. These compounds inhibit corrosion even at very low concentrations in 1M HCl and the aromatic phthalate derivative showed superior inhibition efficiency than the aliphatic maleate derivative. The polarization curves indicate that the compounds are mixed-type inhibitors, affecting both anodic and cathodic corrosion currents. Adsorption of these compounds on the carbon steel surface is in agreement with the Langmuir adsorption isotherm model. The calculated Gibbs free energy values confirm the chemical nature of the adsorption.