Transport of Dense Phase CO2 in C Steel Pipelines--When Is Corrosion an Issue?

Both field experience and lab data indicate that the corrosion rate in pure dense phase CO2 is near zero if no free water is present. It is not confirmed that this also applies when other contaminants like SOx, NOx, H2S and O2 are present in moderate amounts.

In a pipeline network with different type of CO2 sources, the comingling of streams with various impurities can give a very complex mixture, and side reactions like oxidation and decomposition of impurities can be foreseen. An important issue is how the contaminants partition between the various phases during pressure reduction and when free water is present. The corrosion mechanisms under these conditions are not very well understood and it becomes more and more uncertain what will happen when the concentration of contaminants including water increases. The paper will address these issues and discuss recent results obtained in corrosion and partitioning experiments carried out in flow loops and autoclaves.