High temperature corrosion of chromia forming Fe-base alloys by CO2 produces not only oxidation but also carburisation. The corrosion kinetics in CO2-rich gas is found to be increased compared with that in air or oxygen. As a result, higher alloy chromium levels are required to achieve protective chromia formation in CO2. Corrosion reaction mechanisms in CO2 are examined and the internal carburisation of alloys in low carbon activity CO2 gases are analysed based on the variation of 2pO at the interface of oxide and metal. Carbon penetration through chromia oxide scale has been revealed by atom probe tomography. The strategies to resist CO2 corrosion are reviewed by alloying of Si and/or Mn, forming additional diffusion barrier layers, and by adding sulphur to modify oxide grain boundaries to reduce carbon diffusion along the grain boundaries.