A mechanistic model for localized co2 corrosion of carbon steel

A mechanistic model aimed at predicting localized CO₂ corrosion in carbon steel pipelines is under development. The model is built based on galvanic coupling mechanism that was recently explored to be responsible for pit propagation of carbon steel in CO₂ environment. Various phenomena associated with localized corrosion processes, such as electrochemical reactions, chemical reactions, mass transfer, FeCO₃ film formation, passivation, depassivation and repassivation are taken into account in the model to give a complete and realistic description of field conditions.

It was found that an unrealistically high pitting corrosion rate was predicted based on galvanic coupling theory. This was attributed to lack of consideration of solution resistance between anode and cathode. In this work, a solution resistance model was incorporated into the localized corrosion model. Modeling results indicated that consideration of solution resistance is necessary for tackling localized corrosion problems. A case study shows the effects of a number of factors on the corrosion process which are in broad agreement with existing knowledge about localized corrosion.

Keywords: mechanistic model, galvanic, corrosion prediction, CO₂ corrosion, localized corrosion, solution resistance