The Effectiveness of Some Organic Polymers As Corrosion Inhibitors for Carbon Steel and Brass in Acidic Media

Abstract

Three organic polymers were studied as corrosion inhibitors for carbon steel type OLC 45 and brass in 1M H2SO4 and 1M HCl solution using potentiostatic and potentiodynamic polarization methods, electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and metallurgical microscopy techniques. The polymers involved in the study are three sodium polyacrylates hydrophobically modified with linear and cyclo-dodecyl and respectively, dihexyl chain. We suppose that, these polymers inhibit corrosion of metal electrodes by a protective mechanism can be owed to either the adsorption of inhibitor molecules forming a protective film or obtaining a insoluble compound and repairing the porous oxide layers. Experimental data showed that these polymers achieved a significant inhibiting action on brass and carbon steel corrosion and act that a mixed corrosion inhibitors and it could be proved by the effects of polymers on the electrochemical properties of metal electrodes. The adsorption of the polymers on the electrodes surface obeys to the Langmuir isotherm model. The temperature influence on the corrosion behaviour of the metal electrodes in 1M H2SO4 and 1M HCl with and without the inhibitor at 500 ppm was analyzed in the temperature domain from 293 to 313 K. The negative value of thermodynamic parameter like Gibbs free energy of adsorption shows the spontaneity of adsorption process. The experimental results indicated that the corrosion rate have been meaningfully reduced in inhibited solutions when in comparison with the corrosive medium and to increase of the protection effect. Moreover, characterization utilizing FT-IR confirms the adsorption of inhibitors and the constitution of corrosion products on the working electrode surface. EIS and potentiodynamic polarization results demonstrate its corrosion protection capacity. The examined polymers exhibited very good inhibition properties for OLC 45 and brass electrode in 1M H2SO4 and 1M HCl medium while the corrosion current density decreased and the inhibitor efficiency increased with increasing inhibitors concentrations.