Effect of some organic surfactants on corrosion inhibition of steel in sea water

Corrosion inhibition of carbon steel by nonionic polyoxy ethylene (80) monopalmitate (Pa (EO)₈₀), cationic hexadecyltrimethylammonium bromide (HTABr) and anionic sodium dodecyl sulfate (SDS) in sea water has been evaluated by weight loss method, correlated with adsorption measurements and X‐ray analysis. The inhibition efficiency of these compounds increases with their concentration and reaches a maximum value around their critical micelle concentrations (CMCs). The adsorption isotherms of the tested samples exhibit an L‐shape and the experimental data fit the Langmuir adsorption isotherm. The maximum amount adsorbed at the pseudo‐plateau region (G_max) calculated from the Langmuir equation increases in the order SDS < HTABr < Pa (EO)₈₀. The X‐ray spectra showed that the steel surfaces inhibited with these compounds were covered with lepidocrocite (FeOOH). The crystallite size is influenced by the type of the surfactant following their inhibition efficiency in the same order.