| Summary: | In the oil and gas industry, carbon dioxide (CO₂) corrosion is a well-known issue, causing general corrosion and localized corrosion. CO₂ can be dissolved in the aqueous phase, forming carbonic acid (H₂CO₃). This can be dissociated into a hydrogen ion and a carbonate ion that can promote the oxidation reaction. Corrosion inhibitors are chemical substances used for internal corrosion control and their efficiency is influenced by factors such as the rate of injection, fluid characterization, steel microstructure, and hydrodynamics. Although several inhibitor formulations provide outstanding protection for internal corrosion in pipelines, there is a concern about the safety and environmental effects of the traditional inhibitors. Recent efforts have focused on the use of green inhibitors such as ionic liquids due to their non-volatility, non-toxicity, and remarkable corrosion inhibition properties. However, ionic liquids have been studied mainly in environments containing hydrochloric acid (HCl) and sulfuric acid (H₂SO₄); therefore, more research efforts are needed in the potential use of ionic liquids under CO₂ environments. The present work studies the performance of a selected imidazole-based ionic liquid (1-decyl-3methyl-imidazolium chloride) for carbon steel C1018 in a CO₂-saturated 3.5% sodium chloride (NaCl) solution using a Rotating Cylinder Electrode. The tests were conducted at 25 °C and various concentrations of ionic liquids and flow conditions (i.e. turbulent and laminar). The kinetics and inhibition mechanism was studied via Electrochemical Impedance Spectroscopy and Potentiodynamic Polarization, while the adsorption mechanism of the inhibitor was elucidated using adsorption isotherm models. The metal surface was analyzed using Scanning Electron Microscopy. Results show the increase of the resistance to the charge transfer with higher concentrations of corrosion inhibitor at turbulent conditions. Moreover, the Langmuir adsorption isotherm was used to study the adsorption process; the adsorption ...
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