Electrochemical evaluation of API-X100 pipeline steel in simulated carbon dioxide corrosion environments

Corrosion evaluation of API-X100 pipeline steel was performed in simulated carbon dioxide corrosion conditions from selected electrochemical perspectives. Preliminary studies were devoted for studying the effect of the content of bicarbonate species; in aerated and in argon-purged deoxygenated conditions. On a separate scheme, the investigations were then pursued in 1-bar-CO₂-saturated media. The effect of temperature, salinity, acetic acid, and oil content were considered at specific ranges to reveal fairly the environmental effects on corrosion kinetics, passivation, and interfacial mechanisms. Chronological Open Circuit Potential (OCP) variations, polarization potentiodynamics, Electrochemical Impedance Spectroscopy (EIS) were utilized for the electrochemical studies. The corrosion rates increased with the bicarbonate content, higher temperature, upon aeration, upon anodically sensitive chloride addition, and with increased acetic acid content. In bicarbonate solutions, effective passivation was established with broad potential ranges, more facilitated with lower temperature, and in chloride free deoxygenated conditions. Low crude oil amounts were introduced, suppressing corrosion rates, acting dependently on temperature as an anodic and cathodic inhibitor, and influencing passivity with a better efficiency at lower temperatures and with less chloride content. A proposed model for electrochemically driven passivity in oil containing deoxygenated bicarbonate is discussed and selected thermodynamic characteristics for oil adsorption in CO₂-saturated media are presented. At the end of this study, weight loss measurements in autoclave-based 50-psi-CO₂-saturated media at 100°C simulating stratified flows are discussed in brief.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat