The growth mechanism of CO2 corrosion product films

Carbon steel usually has high corrosion rate in water with dissolved CO2 however the steel surface can be covered by protective corrosion product film. Therefore the carbon steel can be widely used in oil and gas industry. This paper discusses the structure, electrochemistry performances, initiation and growth of protective corrosion product films. A duplex layer structure of FeCO3 films was found by electrochemical impedance spectrum (EIS). The physical and chemical situations of solution near carbon steel surface were investigated by ultraviolet spectrophotometry and chronopotentiometry. According to crystallography the growth mechanisms of protective CO2 corrosion product films were discussed.

Research highlights
► The structure of the CO2 corrosion product films are duplex layer, which consist of inner layer and outer layer.
► After outer layer appearing the whole corrosion rate decreases and the protective performance of CO2 corrosion product films is improved.
► The ferrous ion concentration close to the carbon steel surface is very high before out layer forming.
► The crystal grains of inner layer are larger than outer layer usually.