Abstract
The inhibition of iron (Fe, 99.98%) corrosion after its immersion for 60 minutes in freely aerated 3.5% sodium chloride (NaCl) solutions by low concentrations of 3-amino-1,2,4-triazole-5-thiol (ATAT) and 1,1'-thiocarbonyldiimidazole (TCDI) was reported. The experimental tests in this work were open circuit potential (OCP), potentiodynamic polarization (PDP), chronoamperometric current-time (CT), electrochemical impedance spectroscopy (EIS), and in-situ Raman spectroscopy. The OCP and PDP curves indicated that the increased concentrations of ATAT or TCDI reduce the corrosion of Fe by shifting its corrosion potential towards the less negative values. CT tests for Fe at constant potential of -0.50 V vs. Ag/AgCl for 120 min revealed that the ATAT and TCDI molecules inhibit the uniform and pitting corrosion. EIS Nyquist plots confirmed also that the presence of ATAT and TCDI and the increase of their concentrations decrease the corrosion of Fe through increasing the solution and charge transfer resistances. In-situ Raman spectra for iron in chloride solution containing ATAT and TCDI confirmed that the inhibition of iron corrosion is achieved by the adsorption of ATAT and TCDI molecules onto its surface.