Corrosion Inhibition Mechanism of Carbon Steel in O₂/CO₂ Coexisting Environment

Abstract

The electrochemical behavior of carbon steel pipeline in simulated solutions containing different concentrations of inhibitor saturated with O2/CO2 was studied by rotating disk electrode (RDE). After comparison with the results tested in CO2 environment, the effect of O2 on the inhibition performance of inhibitor A on the carbon steel was obtained.Potentiodynamic polarization was used to test the inhibition efficiency of inhibitor A. The EIS was used to study the adsorption behavior of the inhibitor and the corrosion process. The data calculated from the EIS fitting were used to study the adsorption behavior of the inhibitor. The morphology and the compositions of the corrosion product were observed by using SEM and XRD respectively. The results indicate that oxygen weakens the adsorption capacity of the inhibitor, which results in less adsorption film coverage ratio of the inhibitor on the steel surface and decreases corrosion inhibition efficiency. The corrosion products are loose and porous Fe2O3 and FeO(OH) in the environment of O2 and CO2 coexisting. The effective acting time of the inhibitor is shortened owing to the increasing corrosion rate and fast growth of the corrosion products in O2/CO2 environment, which results in more weakened adsorption capacity of the inhibitor.

Keywords

• carbon steel
• O₂/CO₂ corrosion
• inhibitor
• rotating disk electrode
• adsorption isotherm curve
• corrosion electrochemistry