1-Ethyl 3-methylimidazolium thiocyanate ionic liquid as corrosion inhibitor of API 5L X52 steel in H <inf>2</inf> SO <inf>4</inf> and HCl media

Mónica Corrales-Luna, Tu Le Manh, Mario Romero-Romo, Manuel Palomar-Pardavé, Elsa M. Arce-Estrada

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© 2019 Elsevier Ltd The corrosion inhibition behavior of 1-ethyl 3-methylimidazolium thiocyanate, (EMIM) + (SCN) − ionic liquid (IL), on API 5 L X52 steel immersed in 0.5 M H 2 SO 4 and 0.5 M HCl aqueous solutions were studied. The kinetic corrosion parameters were determined using a gravimetrical method and electrochemical tests (polarization curves, electrochemical impedance spectroscopy). The (EMIM) + (SCN) − exhibited good inhibition efficiency, IE, (82.9% and 77.4% for H 2 SO 4 (75 ppm) and HCl (100 ppm) solutions) properties in both solutions acting as a mixed-type inhibitor. In H 2 SO 4 the IE increased with increasing IL concentration and temperature, while in HCl IE decreased with the temperature increase. The IL adsorption mechanism followed the Langmuir isotherm, presenting a competition between the physical and chemical interactions. Surface analysis techniques (energy dispersive spectroscopy and X-ray photoelectron spectroscopy) indicate that the inhibitor formed a protective film on the steel surface, evidencing the adsorption of the cation (EMIM) + and the anion (SCN) − of the IL on the steel surface, which corroborates that both the (EMIM) + and the (SCN) − of IL interact with the substrate. The evaluation of interactions of (EMIM) + (SCN) − molecules with H 2 SO 4 and HCl in the presence of water on different surfaces of iron Fe and Fe 2 O 3 (110) plane was performed, using molecular dynamics to determine the inhibitor adsorption energies in both acid media. The simulation results are in close agreement with the experimental observations that the inhibition efficiency is better in H 2 SO 4 solution in comparison with that in HCl due to the higher adsorption energy values obtained in H 2 SO 4 medium.
Original languageAmerican English
JournalCorrosion Science
StatePublished - 1 Jan 2019

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