Effects of some ions on ion-selectivity of ferrous sulfide film

The ion-selectivity of ferrous sulfide film formed on a cellulose sheet was determined by measuring the film potentials in neutral chloride solution. The results show that ferrous sulfide film is a bipolar film consisting of an inner cation-selective layer and an outer anion-selective layer. This kind of film structure can accelerate the localized corrosion of steel. The influence of some anions, cations and imidazoline corrosion inhibitor on ion-selectivity of the film was also investigated. The ion-selectivity of the film is altered from bipolar to anion-selective with the adsorption of Ca²⁺, Mg²⁺ and Ba²⁺ ions, or to cation-selective with the adsorption of MoO₄^2-, PO ₄^3-and imidazoline inhibitor. Potentiodynamic polarization, AC impedance technology, and the weight-loss method were used to understand the relationship between the ion-selectivity and corrosion behaviors of steel in sulfide-containing solution.