Deterministic Modeling of the Corrosion of Low-Carbon Steel by Dissolved Carbon Dioxide and the Effect of Acetic Acid. I-Effect of Carbon Dioxide.

Carbon dioxide corrosion of carbon steel in brine has been a recognized problem in oil production and it is becoming more common with the use of CO2-flooding as an oil recovery technique. The presence of acetic acid is systematic in oil fields, however, its role in corrosion has not been well-recognized and it is still debated. The present work was carried out, first, focusing on an understanding of CO2-corrosion of low-carbon steel and, later to ascertain the effect of acetic acid. This understanding is achieved by developing a deterministic model that explains and accounts for the experimental observations from Electrochemical Impedance Spectroscopy (EIS) data. The impedance model, based on the Point Defect Model, provides a good account of the formation and growth of a bi-layer that comprises an oxide (inner) layer adjacent the surface and a precipitated (outer) layer of siderite, FeCO3, forming on the top of the inner layer.