For obtaining better oxidation resistance of niobium in air, a niobium silicide
was non-electrolytically deposited onto niobium from the molten salt, where a
disproportional reaction occurs between Na2SiF6,
SiO2, and Si. A single phase of NbSi2 was formed with a
homogeneous thickness of about 10 micro m above 1073 K. The oxidation resistance
of pure niobium with this coating layer was improved. During the oxidation at
the high temperatures, Nb5Si3 was formed at interface between the
Nb substrate and the NbSi2 layer. Due to this intermediate layer
formation, the oxidation resistance became better than for pure NbSi2.