Fluorine substituted thiomethyl pyrimidine derivatives as efficient inhibitors for mild steel corrosion in hydrochloric acid solution: Thermodynamic, electrochemical and DFT studies

Three new 5-fluoro-2- methylthio substituted pyrimidine derivatives have been synthesized and characterized by H-1 NMR spectroscopy and Mass spectrometry. Corrosion inhibition characteristics of the synthesized pyrimidine derivatives have been studied on mild steel (MS) in 0.5 M hydrochloric acid solution at various temperatures (303-333 K) using mass loss and electrochemical techniques. The obtained weight loss, electrochemical impedance and potentiodynamic polarization data indicate that the corrosion inhibition efficiency is directly proportional to concentration of the inhibitors. The Adsorption process on MS surface obeyed Langmuir isotherm model. Scanning electron microscopy (SEM) was used to characterize surface morphology of the MS specimen in absence and presence of pyrimidine derivatives. Density functional theory (DFT) calculations using B3LYP functional with 6-311+G (d,p) level was used to establish the relationship between molecular structure and corrosion inhibition efficiency. Electrochemical analysis indicated that pyrimidine derivatives inhibit the corrosion by adsorbing on the metal surface. Mixed-type of corrosion inhibition activity with anodic predominance was proposed by polarization studies. (C) 2020 Elsevier B.V. All rights reserved.