Iodide-based ionic liquid as corrosion inhibitor of API 5L X52 steel in H2SO4 solution at different flow regimes

The ionic liquid (IL) 1-ethyl-2,3-dimethyl-1H-imidazol-3-ium iodide [DEIM + ]I − was evaluated as corrosion inhibitor (CI) of API 5L X52 carbon steel in a corrosive medium consisting of 1 M H 2 SO 4 at 25 °C. The potentiodynamic polarization (PDP) curves confirmed that the current density ( i corr ) values dropped in the presence of inhibitor due to the blockage of active sites by the adsorption of CI molecules. Likewise, the results obtained by electrochemical impedance spectroscopy (EIS) evidenced that the presence of [DEIM + ]I − affected the phenomena of electric charge transfer in the metal-CI interface, which depended on the CI concentration. Theoretical calculations supported the proposed adsorption mechanism, indicating that the adsorption of [DEIM + ]I − occurred through the cation aromatic ring and I − ion, promoting the formation of covalent bonds on the steel surface, notwithstanding, the IE was inversely proportional to N Re (Reynolds number) because τ RDE (shear stress) reduced the adsorption and orientation of the CI molecules in the metal-solution interface. The SEM surface analysis revealed that [DEIM + ]I − reduced significantly the surface damage caused by the corrosive medium. The high-resolution spectra produced by XPS of C 1 s and N 1 s confirmed the adsorption of DEIM + and I 3d of the anion I − . Finally, the maximal IE values were 90 and 77 % at 150 ppm of CI in stationary and turbulent flow regimes, severally.