Some Polysorbate Compounds as Corrosion Inhibitors for Carbon Steel in Hydrochloric Acid

Abstract

Some commercial non-ionic surfactants polysorbate, namely, polysorbate 80, polysorbate 40 and polysorbate 20, were tested as inhibitors for corrosion of C-steel in 2.0M HCl solution using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. It was found that all the three used compounds act as inhibitors for acid corrosion of C-steel. The inhibition efficiencies obtained by the three techniques were almost the same, and increase with increasing the hydrocarbon chain length and the surfactant concentration. The polarization studies show that these compounds act as mixed inhibitors. The inhibition action of these surfactants can be explained by their ability to adsorb on the metal surface making a barrier to mass and charge transfer.  It was found that the adsorption of these surfactants follows Langmuir adsorption isotherm. The negative values of  adsorption free energy indicating that the adsorption process is spontaneous and increases, for different surfactants, in the same direction as inhibition efficiency.