On Methodology for Reliable Corrosion Testing of Pipeline Steel in Dense Phase CO2

Reliable assessment of the corrosion rate of pipeline steel in dense phase CO2 is critical for the safe and cost-effective deployment of carbon capture (utilization) and storage (CCS or CCUS) infrastructure. However, a standard test methodology for such complex environmental conditions (multi-impurities, temperature, pressure, and flow) is yet to be established, and the most commonly used approaches to laboratory testing have been shown to yield highly irreproducible results, even under relatively simple conditions. This study aims to establish a robust and reliable corrosion test method in a model system consisting of H2O and O2 impurities in dense phase CO2 at ambient temperature and 80 bar. Test protocols for efficient deaeration, rapid test environment establishment, control of impurity concentration, and efficient depressurization are systematically studied and their reliability validated using impurity concentration analysis and postexposure inspection of pipeline steel specimens. The established methodology is demonstrated to eliminate undesirable experimental artefacts. Using the improved protocol, good repeatability in corrosion rate measurement of X65 steel as a function of exposure time is observed in H2O-saturated dense phase CO2.