Synergistic Inhibition Effects of Sodium Octylthiopropionate and Various Metallic Cations on Iron Corrosion

Abstract

Synergistic inhibition effects of sodium octylthiopropion-ate NaC₈H₁₇S（CH₂）₂CO₂（NaOTP） and various metallic cations were investigated on iron corrosion in aerated 0.5 M Na₂SO₄ by polarization measurement and X-ray photoelectron spectroscopy （XPS）. Lower inhibition efficiencies than the efficiency of 3×10^－4 M NaOTP alone were obtained by the addition of 1×10^－4 M cations, Al^3＋, Ga^3＋, Y^3＋, La^3＋ and Ce^3＋ to the solution where precipitates formed. Although clear solutions appeared by reducing the concentration of the cations, no synergistic inhibition effect of NaOTP and the cations on iron corrosion was observed. Addition of 1×10^－4 M Zn^2＋ to the 3× 10^－4 NaOTP solution, in which no precipitate formed, resulted in synergistic inhibition. XPS showed on the iron surface covered with a chelate precipitate composed of OTP^－ and Zn^2＋.