Does hydrogen affect oxygen permeability in alloys?

• The diffusion control applies to the internal oxidation of Pd-1%Cr alloy.
• The oxygen permeation No(s)Do was constant for high pO2pO2 gases with different water vapour contents
• Hydrogen has no influence on oxygen permeability in chromium-containing alloys.

Water vapour and/or steam are well known to accelerate breakaway oxidation of chromia-forming alloys. Some authors have proposed that hydrogen promotes internal oxidation of chromium, resulting in breakaway oxidation. We tested this hypothesis by directly measuring oxygen permeability after oxidation in high pO2pO2 atmospheres containing water vapour. Palladium with 1 wt% chromium alloy was oxidized in dry and wet Ar-1%O2 at 850 °C. The internal oxidation in all cases obeyed parabolic kinetics. The oxygen permeability deduced from Wagner's diffusion model showed small differences in the internal oxidation of the Pd-1Cr alloy in these gases. We conclude that hydrogen has no influence on oxygen permeability in chromium-containing alloys.