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During carbon dioxide storage technology (carbon capture and storage, CCS) components are exposed to a corrosive environment and mechanical stress, which results in corrosion fatigue and inevitably followed by the a lifetime reduction of these components. In order to gain knowledge upon the corrosion fatigue strength of materials, Samples of high alloyed stainless injection-pipe steels AISI 420 X46Cr13, and X5CrNiCuNb16-4 AISI 630 were tested in a at T=60 °C and ambient pressure in a CO2-saturated synthetic aquifer environment similar to possible geological on-shore CCS-sites in the northern German Basin. Therefore a corrosion chamber applied to a resonant testing machine allowing for “in situ” test conditions was designed and successfully tested. In-situ tension compression experiments were established using a resonant testing machine at a frequency as low as 30 – 40 Hz. In addition technical CO2 was introduced into the closed system at a rate close to 9 L/h to keep stable environmental conditions. Simultaneously electrochemical testing was performed to get information on failure causes and the mechanism of failure during the injection of CO2 into deep geological layers. S-N plots, micrographic analysis, and surface analysis of the fracture surface were applied to obtain sustainable information on the corrosion fatigue behavior of injection pipe steels. Samples used have a surface roughness of Rz = 4, to simulate technically machined surfaces. X46Cr13 reached the maximum number of cycles (12.5 x 106) at a stress amplitude of 173 MPa. X5CrNiCuNb16-4 reached the maximum number of cycles (10 x 106) at a stress amplitude at 150 MPa. The scatter range of X5CrNiCuNb16-4 is very high (1:34); by comparison the scatter range of X46Cr13 is only 1:3.5.
Samples of differently heat treated high alloyed stainless injection-pipe steels AISI 420 X46Cr13, AISI 420J X20Cr13 as well as X5CrNiCuNb16-4 AISI 630 were kept at T=60 °C and ambient pressure as well as p=100 bar for 700 h - 8000 h in a CO2- saturated synthetic aquifer environment similar to possible geological on-shore CCS-sites in the northern German Basin. Corrosion rates and scale growth are lowest after long term exposure for steels hardened and tempered at 600 to 670 °C and pits - indicating local corrosion- decrease in diameter but increase in number as a function of carbon content of the steel. Martensitic microstructure is preferred with respect to this particular CCS-site.
During carbon sequestration the CO2-induced corrosion of injection pipe steels is a relevant safety issue when emission gasses are compressed into deep geological layers. The reliability of the high alloyed steel X35CrMo17 suitable as injection pipe for the geological onshore CCS-site (Carbon Capture and Storage) in the Northern German Basin, is demonstrated in laboratory experiments in equivalent corrosive environment (T = 60 °CC, p = 1–100 bar, aquifer water, CO2-flow rate of 9 L/h, 700–8000 h exposure time). Corrosion kinetics and microstructure were characterized and compared to other potential injection pipe steels (42CrMo4, X46Cr13, X20Cr13 and X5CrNiCuNb16-4).