Corrosion of pipelines in CO2-saturated oil-water emulsion flow studied by electrochemical measurements and computational fluid dynamics modeling

In this work, corrosion of a X65 pipeline steel in CO2-saturated oil-free solutions and oil-water emulsions was investigated using a home-made pipe flow system by various electrochemical measurements and computational fluid dynamics (CFD) simulation. It is found that, in both oil-free solutions and oil-water emulsions, the mass-transfer of corrosive species, such as H+ and H2CO3, dominates the cathodic process during corrosion of the steel. With the increase of the flow velocity, the mass transfer is accelerated, contributing to increased corrosion. The presence of oil in the fluid decreases the steel corrosion, and the effect is amplified with the increasing oil content. This is attributed to the increased opportunity that the pipe wall becomes oil-wetting when the fluid contains more oil. The CFD simulation and the parameter derivation, combined with a semi-empirical model, are able to predict the corrosion rate of steels in CO2-saturated oil-water emulsion flow.