Predicting Localized CO2 Corrosion in Carbon Steel Pipelines

A mechanistic model is being developed with the aim of predicting localized CO₂ corrosion in carbon steel pipelines. The model is built based on a galvanic coupling mechanism proposed to be responsible for pit propagation of carbon steel in a CO₂ environment. Various phenomena associated with the localized corrosion process, such as electrochemical reactions, chemical reactions, mass transfer, FeCO₃ film formation, passivation, depassivation and repassivation are taken into account in the model to generate a complete and realistic simulation of field conditions.

Both uniform and localized corrosion rates can be predicted depending on how corrosion condition evolves with time. The model calculates the change of corrosion condition at each time step to determine if a uniform or localized corrosion model should be used. In addition, this model provides users with other valuable information, such as local water chemistry, fluxes of species, and film morphology to help users understand the corrosion process. A parametrical study shows the effect of a variety of factors on the corrosion process which is in agreement with common knowledge about localized corrosion.

KEY WORDS: mechanistic model, galvanic, corrosion prediction, CO₂ corrosion