[en] Elucidating the relationship between coolant parameters and corrosion of materials proposed for Generation IV supercritical water-cooled reactors (SCWRs) remains a challenge. The properties of the supercritical water (SCW) coolant change significantly from core inlet (∼350 ^oC, 25 MPa) to outlet (as high as 625 ^oC, 25 MPa). A mechanistic framework is required to interpret materials degradation data and predict long-term behaviour. Different corrosion mechanisms exist in high-density sub-critical/near-critical water and in low-density SCW. Understanding surface, rather than bulk, coolant chemistry is required; for example, the structure of SCW near the surface and the local oxide solubility. Oxide solubility also determines the transport of radioactive species out of the core. This paper describes the link between the physical chemistry of SCW and the corrosion of SCWR materials, including corrosion product release. (author)