Inhibitory activity investigation of a new nitrogen-containing surfactant in an acid medium

In this paper, the results of testing a new nonionic surfactant as a corrosion inhibitor in a 0.5M hydrochloric acid solution are given. The corrosion inhibitor was synthesized by catalytic esterification of maleic anhydride with polyoxyethylene sorbitan and further amidating of the ether with diethanolamine. The structure and composition of the developed inhibitor were characterized by the methods of FT-IR and H-1 NMR spectroscopy. Results showed that the reagent MA/Tween-DEA effectively inhibited the corrosion of carbon steel in hydrochloric solution with an optimal inhibition efficiency of 94 % (100 ppm) at 303 K from weight loss test. Thermodynamic parameters such as adsorption heat (Delta H-a), adsorption entropy (Delta S-a) and adsorption free energy (Delta G(ads)) were obtained from experimental data of the temperature studies of the inhibition process at five temperatures ranging from 303 to 343 K. The thermodynamic parameters of the corrosion process were calculated in the absence and presence of inhibitor and discussed. The mechanism of action of inhibitor protection of a steel plate by a synthesized inhibitor has been studied. Adsorption of MA/Tween-DEA on the carbon surface in 0.5 M HCl follows the Langmuir isotherm model.