Impact of High Temperature and Pressure to Steel Passivation in {CO}2 Atmosphere.

The corrosion behaviour of AISI 347 in 0.1 M sulfuric acid at temperatures 50 and 75 °C and pressures up to 300 bar in a CO2 atmosphere was studied by surface analysis and electrochemical methods. Corrosion reactions in which CO2 is present accelerate the formation of a protective FeCO3 layer, but the success of such a passivation depends on the saturation concentration and the corresponding temperature. Significantly better results compared to untreated steels were obtained at lower temperatures by increasing the pressure. To explain the differences in corrosion rates between samples, the activation energy for the layer dissolution was also discussed. It can be assumed that the compressibility of the CO2 at different pressures has an influence on the formation of the protective iron carbonate layer and its properties and thus to on the corrosion behaviour.