Abstract
The influence of metal orientation and the prior oxide film on the oxidation rate of nickel single crystals has been investigated at 600°C in 
Torr oxygen using a manometric technique and the specimens examined before and after oxidation by electron diffraction, x‐ray emission analysis, and electron microscopy. For nickel electropolished in sulfuric acid, the order of decreasing oxidation rate is found to be (100), (111), and (112). This anisotropy together with changes in oxidation rate with surface pretreatment can be explained by modification in the structure of the prior oxide; when a single orientation prior oxide persists the oxidation rate is low; when the oxide contains twin orientations or becomes polycrystalline, the oxidation rate is increased. The results may be interpreted in terms of a variation in the number of easy diffusion paths in the oxide; the higher the density of these paths the greater is the oxidation rate.