Fundamental Aspects of CO₂ Metal Loss Corrosion, Part I: Mechanism

Abstract

A large number of CO₂ dependent chemical, electrochemical and mass transport processes occur simultaneously on and close to the corroding steel surface. The various reactions respond differently to changes in CO₂ partial pressure, temperature, water chemistry, flow and other operational parameters. Apparently contradictory observations and results have been reported when these reactions have been studied. The present paper discusses the current understanding of these fundamental CO₂ corrosion mechanisms with particularly focus on how CO₂ affects the water chemistry and the electrochemical reactions on the bare steel surface. As many sweet systems contain organic acids that affect the solution chemistry and the formation and stability of the FeCO₃ corrosion product films, some specific effect of organic acids is also addressed.