The CO2 corrosion inhibition of a high strength pipeline steel by hydroxyethyl imidazoline

The corrosion inhibition of a X-80 pipeline steel in saltwater saturated with CO2 at 50 °C with hydroxyethyl imidazoline has been evaluated by using electrochemical techniques. Techniques included polarization curves, linear polarization curves, electrochemical impedance and electrochemical noise measurements with inhibitor concentrations of 0, 5, 10, 25, 50 and 100 ppm. Results showed that this inhibitor was an anodic-type inhibitor and the best inhibitor efficiency was reached with 25 ppm, and it increased as time elapsed. The corrosion process was different for inhibitor depending of its concentration; for doses lower than 25 ppm the process was under intermediate species adsorption control, whereas for 25 ppm of inhibitor concentration, the corrosion mechanism was under a mixed charge transfer and diffusion control. The monitoring of the film formation could be followed by using electrochemical noise measurements.