The corrosion behaviour of alloy 690 tube in simulated PWR secondary water with the effect of solid diffusing hydrogen

Highlights: • High temperature water corrosion test was performed in hydrogen permeation condition. • The thickness of Cr-rich inner films has no obvious change by hydrogen permeation. • Sheet-like outer oxides on hydrogen-permeating samples unlike hydrogen-free ones. • Fe and Ni-rich spinel-type outer oxide films formed on hydrogen-free specimens. • Cr-rich chromia-type outer oxide films formed on hydrogen-permeating specimens. - Abstract: High-temperature water corrosion tests were performed to investigate the corrosion behaviors of Alloy 690 TT in simulated PWR secondary water with gaseous hydrogen permeation condition. Double-layer oxide films formed on hydrogen-free and hydrogen-permeating specimens. The thickness of a Cr-rich inner oxide film on the hydrogen-free specimens has no obvious difference from the hydrogen-permeating ones. For hydrogen-free specimens, the outer oxide films were Fe and Ni enriched spinel-type oxide particles. For hydrogen-permeating specimens, outer oxide films were sheet-like or needle-like Cr-rich chromia-type oxides. In summary, the solid diffusing hydrogen affected the morphology and composition of outer oxides.