Hydrogen permeation into iron

The permeation of deuterium (D) from the gas phase into solution in iron has been measured using a new method based on ion beam analysis. For bare metal surfaces the D uptake was observed to be limited by matrix diffusion through the bulk. The influence of chemisorbed oxygen on the D uptake rate was examined in detail. Submonolayer coverages of oxygen caused the D uptake to become surface-limited and reduced the D uptake rate by orders of magnitude. The temperature dependence of the surface-limited uptake rate suggests that a molecular precursor state may be involved in the D uptake for oxygen covered surfaces. The evidence indicates that chemisorbed oxygen reduces the D uptake and release rates by blocking sites where D can be chemisorbed on the surface.