Comparative study on the influence of hydrodynamic conditions in the corrosion behavior of a 1018 carbon steel using a green inhibitor in brine-CO2 solution

The corrosion behavior of a 1018 carbon steel was studied by electrochemical techniques under hydrodynamic conditions employing N-hydroxyethylimidazoline derivatives of avocado oil as a green corrosion inhibitor. The corrosion behavior of the steel surface under hydrodynamic flow conditions before and after the addition of the green corrosion inhibitor was evaluated by means of the rotating cylinder method using rotation speeds of 0, 10, 100, 500, 1000, and 2000 RPM. The inhibitor concentration was set at 25 ppm (7.29x10(-5) mol/L) in all conditions studied. The results display a high corrosion resistance of the carbon steel surface at a rotation speed of 1000 RPM in the absence of inhibitor, which is attributed to the formation of a protective FeCO3 layer. When the inhibitor is added to the electrolyte, the highest corrosion resistance is observed for the samples evaluated under static conditions and the lowest rotational speeds. In the presence of the inhibitor, the carbon steel surface shows a decrease in the corrosion resistance as the rotation speed increases above 500 RPM. Interestingly, the addition of the inhibitor promotes a uniform corrosion process on the steel surface under zero rotation and low rotational speeds, and a localized corrosion process for high rotational speeds, respectively. The results suggest that dynamic conditions are associated to a change in the inhibitor concentration at the metal surface, which influences in a negative way the protective effect of the inhibitor.