The utilization of ionic liquids as sustainable and eco-friendly inhibitors for corrosion protection of carbon steel in petroleum fields

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Various ionic liquid compounds are synthesized from the combination of iminodiethanol and fatty acid of butyric (IL-4) caprylic (IL-8) and capric (IL-10). The composition of such compounds was confirmed by various spectroscopic techniques and was tested as mitigators for the destruction of carbon steel in 10 % diluted oil field-produced water. The measurements of electrochemical potentiodynamic polarization, impedance spectroscopy, and gravimetry were complemented by surface investigation of some corroded carbon steel samples utilizing scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX). The data indicated that the addition of IL-4, IL-8, and IL-10 inhibits the destruction of carbon steel in the 10 % diluted oil field-produced water by lowering the corrosion current density (Iorr) and the double-layer capacitance (Cdl). Tafel polarization data confirmed that the studied compounds acted as mixed inhibitors. The values of the cathodic Tafel slope, bc, are found to be close to each other confirming that the adsorbed compounds did not alter the mechanism of hydrogen evolution. The charge transfer resistance, Rct, for the blank solution is 1501 and increased with the addition of such compounds to reach 5332 at a concentration of 500 mg/l of IL-10 with a protection efficiency of 85.83 %, at 25 ◦C. The computed -ΔG°ads values varied between −18.11 and –23.98kJ mol/1 depending on the type of inhibitor and the temperature, which confirms the suggestion of the physisorption mechanism. The negative values of ΔG°ads explain the spontaneity of the adsorption process. The lowering in Kads values with T is attributed to the escaping of some of the adsorbed inhibitor molecules leaving the carbon steel surface. Theoretical quantum computation was used to confirm the adsorption ability of various ionic liquids on the examined metal.