Evaluation of chitosan and carboxymethyl cellulose (CMC) as ecofriendly corrosion inhibitors for X60 pipeline steel in CO₂ saturated 3.5% NaCI solution

One of the cost-effective methods for controlling carbon steel corrosion in the oil and gas production is the use of chemical corrosion inhibition. However, there is an increasing need in the industry to limit the use of chemicals, mainly due to more severe environmental impact, and current research are focused on search for greener alternatives. In this study, the performance of two green inhibitors; chitosan and carboxymethyl cellulose (CMC), on a typical X60 pipeline steel in C0₂ saturated 3.5% NaCI solution were investigated in both static and dynamic conditions using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques. Also, metal surface characterization was performed using scanning electron microscope (SEM). The results indicate that there is a remarkable difference in inhibition efficiency of each inhibitor on the low carbon X60 steel. Inhibition efficiency increased with the increase of Chitosan and CMC concentrations. Immersion time was found to have a profound effect on the corrosion inhibition performance of each inhibitor. Even though the inhibition efficiency decreased with the increase in temperature, still both Chitosan and CMC act as good corrosion inhibitors for X60 steel. The rotating cylinder electrode (RCE) was used to study the rate of corrosion under high velocity (high shear, turbulent) flow conditions and the results revealed that the inhibition efficiency of Chitosan decreased in the dynamic condition while the same increased for CMC. Potentiodynamic polarization results (not included in this report for lack of space),reveal a mixed-type inhibition for both systems of inhibitors. The adsorption of each inhibitor on the steel surface obeys Langmuir's isotherm.