EFFECT OF TRACE DISSOLVED OXYGEN ON THE CATHODIC KINETICS OF CARBON DIOXIDE CORROSION OF CARBON STEEL

摘要

The corrosion of carbon steel in carbon dioxide saturated brine solutions is controlled by a mixed activation-mass transfer process in the cathodic reaction mechanism. Cathodic polarisation curves of carbon steel in carbonic acid solutions exhibit a limiting current behaviour that is dependent on the rate of mass transfer. In studies using the jet impingement technique, the magnitude of this limiting current behaviour has been found to be strongly affected by the presence of trace levels of dissolved oxygen. This paper presents a theoretical assessment of the mass transfer limited cathodic current to illustrate the pronounced effect of dissolved oxygen contamination <15 ppb. Discussion is presented regarding the implications of dissolved oxygen contamination on the interpretation of the mechanism of carbon dioxide corrosion.