Two novel thiadiazole derivatives as highly efficient inhibitors for the corrosion of mild steel in the CO2-saturated oilfield produced water

The corrosion of mild steel pipelines is a tough issue during the extraction of oil and gas. In this work, two novel thiadiazole derivatives, 5-(benzylthio)-1,3,4-thiadiazol-2-amine (BTTA) and 5,5'-disulfanediylbis (1,3,4-thiadiazol-2-amine) (DSTA), were synthesized as inhibitors for the corrosion of mild steel in the CO2-saturated oilfield produced water. Their inhibitive effects and mechanisms were studied by electrochemical measurements, surface characterization, quantum chemical calculations and molecular dynamics (MD) simulations. It is shown that both DSTA and BTTA exhibit high inhibition efficiencies. Especially for DSTA, the inhibition efficiency reaches 98.7% even in a fairly low concentration of 0.0025 mM, and reaches 99.37% with a concentration of 0.025 mM. DSTA presents a better inhibitive performance than BTTA in low concentration. These two thiadiazole derivatives act as mixed type inhibitors with predominant anodic effectiveness, and their adsorptions on mild steel surface follow the Langmuir adsorption isotherm. According to the experimental results and theoretical calculations, the inhibitive mechanisms of BTTA and DSTA are discussed. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.