Investigation on the corrosion inhibition of two newly-synthesized thioureas to mild steel in 1 mol/L HCl solution

摘要

Two kinds of thioureas, 1-N-(1'-(1',2',4'-triazole))acetyl-4-N-benzoylthiosemicarbazide (TBU) and 1-N-(1'-(1',2',4'-triazole))Methyl-4-N-(3aEuro(3),5aEuro(3)-dimethyl)benzoylthiosemicarbazide (TDBU) were synthesized and characterized as corrosion inhibitors in 1 mol/L hydrochloric acid to mild steel by weight loss measurement, electrochemical measurement, quantum chemistry calculation and molecular dynamics simulation. The results demonstrate that TBU and TDBU are good inhibitors that could reduce anodic dissolution and retard the hydrogen evolution reaction with the order TBU TDBU, and that the corrosion inhibition efficiency increases with the increasing thiourea concentration. TBU has a remarkably high inhibition efficiency of 97.5% at a concentration of 1.0 x 10(-3) mol/L. The adsorptions of TBU and TDBU on mild steel accord with the Langmuir model. The results of quantum chemical study indicate that the S atom contributes to the adsorption of the corrosion thiourea molecules. The steric hindrance of the methyl group, not an electronic effect, was suggested as the main influencing factor on the inhibition efficiency of the two thioureas, which is relatively rare in literature reports.