The inhibition action of some organic polymers on the corrosion carbon steel in acidic media

Abstract

Corrosion inhibition performance of three sodium polyacrylates polymers was analyzed for carbon steel type OLC 45 in 0.5 M H2SO4 solution. Effectiveness of this polymers were investigated by 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 this study are three sodium polyacrylates hydrophobically modified with linear and cyclododecyl and, respectively, dihexyl chain (NaPADD, NaPACDD and NaPADH). We assume that, these polymers prevent corrosion of metal electrodes by a protective process can be due to either the adsorption of inhibitor molecules building a protective film or achievement an insoluble complex. Results showed that these polymers accomplished a considerable inhibiting action on OLC 45 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 behavior of the metal electrodes in 0.5M H2SO4 with and without the inhibitor at 800 ppm was analyzed in the temperature domain from 293 to 333 K. The negative value of thermodynamic parameter like Gibbs free energy of adsorption shows the spontaneity of adsorption process. The characterization by FT-IR and SEM confirms the adsorption of inhibitors and the formation of corrosion products on the working electrode surface. EIS and potentiodynamic polarization data were indicative its corrosion protection ability. The best inhibition of 97% gets at an inhibitor concentration of 800 ppm for NaPACDD.