The role of dissolved oxygen in the corrosion of titanium and zirconium by liquid sodium

The corrosion of titanium and zirconium by liquid sodium containing dissolved oxygen has been shown to take place by the formation of non-adherent ternary oxides, in addition to the well known binary oxides, and oxygen solid solution in the metals. The compounds Na4TiO4 and Na2ZrO3 have been identified on the surface of titanium and zirconium after immersion in liquid sodium containing dissolved oxygen at temperatures close to 600 °C. The oxides were identified by their X-ray powder diffraction patterns which were recorded through a matrix of sodium. The lattice parameters of the underlying transition metal were measured enabling the approximate amount of oxygen in solid solution in the metal to be calculated. The characterisation of ternary oxide corrosion products, in addition to binary oxides and solid solutions of oxygen in the metal, enables a comprehensive mechanism of corrosion for titanium and zirconium in the presence of liquid sodium to be postulated.