The Counter Ion Influence of Cationic Surfactant and Role of Chloride Ion Synergism on Corrosion Inhibition of Mild Steel in Acidic Media

摘要

The corrosion inhibition of mild steel in 0.5 M H2SO4 solution by cationic surfactants, cetylpyridiniumchloride (CPC) and cetylpyridinium bromide (CPBr) was studied by potentiodynamic polarizationcurves. The results showed that the counter ions of these surfactants, i.e., chloride and bromide, and theaddition of chloride ion to any of the surfactants significantly influenced the protection efficiency(Picor) and mode of inhibition. Surfactants alone and in combination with chloride ions were found toobey Temkin adsorption isotherm. Chemical adsorption was proposed from the obtainedthermodynamic parameters such as the free energy of adsorption, . The synergism parameter(S莹), as a quantitative estimation of the interaction of surfactants and chloride, was found to be greaterthan unity indicating that the enhanced protection efficiency caused by the addition of chloride ions tothe surfactants is due to a co-operative adsorption of both species. The experimental data and the- - extracted thermodynamic parameters confirmed the role of the counter ions (Cl and Br ) which has- been confirmed by the addition of Cl ions as additive for synergism effects.