The main aim of this work was to discover how dry hydrogen corrodes the uranium alloy UV 0.095 at 70°C ([ H 2 O] < 4 ppm) and to understand the inhibition of this reaction by carbon monoxide. On polycrystalline samples we observed marked localization of the corrosion in pits. The hydriding reaction was monitored by optical microscopy which showed that the attack on the metal took place under the oxide layer and spread until this layer ruptured. When small amounts of carbon monoxide (1%–10%) were added at the same time as the hydrogen, the corrosion of the alloy was then observed in many delocalized microscopic pits whose growth was extremely slow. We explain this marked slowing down by preferential adsorption of the carbon monoxide with respect to hydrogen at the metal-metal oxide interface.