The role of pit corrosion in engineering the carbon storage site at Ketzin, Germany

The role of pit corrosion needs to be considered to guarantee reliability and safety during the injection of compressed emission gasses - mainly containing CO2 - into deep geological layers (CCS-technology, Carbon Capture and Storage). Therefore, laboratory experiments were carried out under the distinct synthetic aquifer environment saturated with technical CO2 at a flow rate of 2 l/h found at the CCS-site at Ketzin, Germany. To determine the local corrosion behaviour, different pipe steels with 1% Cr 0.42% C (42CrMo4) and 13% Cr 0.46% C (X46Cr13) were compared. The samples were heat treated for up to 2 years and the reaction kinetics were determined. Pits were formed exclusively on the high chromium bearing steels. Pit heights and diameters were measured and a precipitation model was derived from the phases found within the complicated multilayer corrosion phases, such as siderite FeCO3 and goethite alpha-FeOOH. Manganese and chromium carbides were found to be possible initial causes for the ongoing pit corrosion.