Synergistic Effect Of Iodide Ions Research Articles

Effect of iodide ions on the synergistic inhibition of the corrosion of manganese-14 steel in acidic media

We investigate the synergistic effect of iodide ions on the corrosion inhibition of manganese-14 steel in 0.5 M H 2SO 4 in the presence of cyclohexylamine using potentiodynamic polarization and linear polarization techniques. In 0.5 M H 2SO 4, the corrosion rates of the steel decrease when amine the concentration decreases, while the inhibition efficiencies increase. The addition of iodide ions enhances the inhibition efficiency considerably. The presence of iodide ions increases the degree of surface coverage, while at low concentrations cyclohexylamine forms an insoluble complex by undergoing adsorption. The synergism parameters ( S θ ) calculated from surface coverage in the case of cyclohexylamine are found to be larger than unity. In addition, the adsorption of this amine on manganese-14 steel is found to follow a Langmuir isotherm. Thus inhibition occurs by adsorption.

Technical Note:Synergistic Effect of Iodide Ions on Inhibitive Performance of Substituted Dithiobiurets during Corrosion of Mild Steel in Hot Hydrochloric Acid

Abstract Four substituted dithiobiurets (i.e., 1,5-diphenyl-2,4-dithiobiuret [DPDTB]; 1-anisidyl-5-phenyl 2,4-dithiobiuret [APDTB]; 1-tolyl-5-phenyl 2,4-dithiobiuret [TPDTB]; and 1-cholorophenyl-5-phenyl 2,4-dithiobiuret [CPDTB]) were synthesized to study their inhibiting effect on mild steel (MS) corrosion in 5 N hot hydrochloric acid (HCl). The synergistic effect of these compounds with potassium iodide (KI) was studied at different concentrations, temperatures, and immersion periods by weight loss and potentiodynamic polarization methods. All compounds showed good inhibition efficiency (IE) at all temperatures and showed the enhancement in IE with the addition of small amounts of KI. Potentiodynamic polarization studies showed that APDTB and DPDTB are predominately cathodic inhibitors, whereas TPDTB and CPDTB are mixed inhibitors. The adsorption of all these compounds followed Temkin's adsorption isotherm.