The Progress Of SPP Oxidation In Zircaloy-4 And Its Relation To Corrosion And Hydrogen Pickup

•Valence mapping of oxidized second phase particle oxidation in zirconium alloys has been successfully achieved by EELS.•Valence change has revealed that Cr and Zr oxidize preferentially, while Fe remains metallic for longer.•Cr oxidation is complete prior to transition.•Fe only oxidises when in full contact with the environment (via water in cracks or nanopores) after transition.