Corrosion and chemical reactions in impure CO2

•Introduction, explain the development in CCS industry (fast groing challenge of hub project mixing different sources of CO2, causing effects of impurities from different sources cause impact on integrity and interact to cause even more issues.•Impurities (H2O, SO2, H2S, O2 and NO2) chemical interactions and their limits, testing background, solubility limits and model.•Results, identified limits from testing and medelling.•Review oif results and put them in perspective, when and how do impurtities react and what are the identified limits and potential results of acid drop out.•Explaining the corrosion mechanism bridging the results toward practical applications and potential consequences (corrosion rates).•Corrosion control options.•Summary and guidance, including identified safe limits, testing and modelling, corrosion management and gaps and way forward. Carbon Capture and Storage (CCS) involves capturing, treating, transporting and storage of CO2 to ensure long-term isolation from the atmosphere. In recent years there has been a significant increase in CCS project proposed and initiated. A number of these proposed projects aim to capture CO2 from multiple industrial emitters (sources) to reduce the carbon footprint for these emitters. Depending on the CO2 composition and operating conditions, separate phases may be formed. It has been identified that these separate phases can comprise of water or reaction products including strong acids, or sulphur that can cause severe corrosion. To ensure long term integrity of the facilities, a safe project CO2 specification needs to be identified. Tight control of CO2 stream composition and operating conditions together with the selection of suitable materials are essential to ensure the integrity for all operating scenarios including upsets. This paper focuses on identification of impurity limits for a CCS project, which are captured in a project's CO2 specification. Special attention is given to one specific group of impurities that can react and cause drop-out of a highly corrosive phase. Sound understanding of the mechanisms that stand behind these chemical reactions, thermodynamics, the role of phase behaviour and potential consequences are needed to be able to identify or/and adjust impurity limits for a CO2 specification in projects. This work aims to improve understanding provide guidance and to reveal knowledge gaps that require addressing in order to identify a safe CO2 specification for a CCS project.