1. Scope

Keywords

Rationale

1. Why is there a need for this new standard? The pipeline steel for CO2 transportation is usually carbon steel, such as X52, X65, and X70. In CCS, the transported-CO2 streams always contain certain amounts of aggressive impurities, such as H2O, O2, H2S, SO2, NOx, depending on CO2 sources and the capture/separation technologies applied. CO2 pipeline steels may suffer severe corrosion degradation problems due to the attack by impurities, thus deteriorating the operational integrity of CO2 pipeline transportation systems. The water is determined to be the most crucial factor in all the potential impurities considering the occurrence and extent of corrosion.If the water content within the CO2 stream is below its saturation limit, the water is dissolved in the CO2 and only the water under-saturated CO2 phase is present in the pipeline. If the water content within the CO2 stream is beyond its solubility limit, a water-saturated CO2 phase exists in the upper part of the pipeline, and a separate aqueous phase accordingly deposits at the bottom of the pipeline. There are no recognized standards for corrosion testing in the CO2-rich phase, and many different approaches are used. There is a large variation of the reported corrosion rates for the condition when the water is fully dissolved in the CO2-rich phase. Some laboratories measured insignificant corrosion rates (0.003 mm/y) while other laboratories reported corrosion rates as high as 2.5 mm/y, which means that the difference is over 800 times. This may cause misleading conclusions. Such enormous experimental difference was caused by the experimental approachs, including the control of water throughout the experiments’ duration, the method of loading of CO2 during start-up, injecting liquid water, the rate of CO2 pressurisation and depressurisation, and others. In order to reduce the variability in the test results, it is necessary to develop a standard corrosion measurement method for the CO2-rich phase. 2. How will it be used and who the users are? The researchers, professors and students in the corrosion engineering, corrosion engineers, pipeline designers in CO2 pipeline area will use it to understand the corrosion in the CO2-rich phase and the effect of impurities on the corrosion in the CO2-rich phase. The test results may be helpful for decision-maker and corrosion management personnel.