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

Abstract

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.