Application of some commercial nonionic surfactants in the field of corrosion inhibition

The adsorption of series of commercial nonionic ethoxylated fatty acid surfactants Co(EO) n (where n = 20, 40, and 80) onto low carbon mild steel is investigated at 25 °C in 0.25 M H 2 SO 4 . The adsorption isotherms of both Co(EO) 20 and Co(EO) 80 are L-shaped representing the formation of a monolayer while Co(EO) 40 was beginning by an L-shaped followed by the formation of a multilayer. The level of the plateau shown by these samples decreases in the order Co(EO) 80 > Co(EO) 20 > Co(EO) 40 . The effect of this adsorption on the protection of steel against corrosion in sulfuric acid has been studied. Potentiodynamic polarization studies clearly reveal the fact that these surfactants act as mixed-type inhibitors. The inhibition efficiency increases with increasing the concentration as well as the hydrophilic chain length of these compounds.