REFERENCES

stage, the rate of oxidation decreased to a negligible value. Vacuum annealing metalIographically polished aluminum in the temperature range 500~176 caused formation of an oxide film which was more resistant o oxidation. Reaction rate results were interpreted according to a parabolic law of oxidation. Values of 37.9 and 41.0 kcal/ mole were determined for the activation energy of reac-tion in the thin film range for specimens vacuum an-nealed at 500 ~ and 600 ~ respectively. A mean value of 37.2 kcal/mole was obtained for the energy barrier against ion diffusion at the metal/oxide interface by at-taching equal significance to results from gaseous and anodic oxidation. An increase in the magnitude of the energy of activation at larger film thickness and the cessation of oxidation have emphasized the limited ap-plicability of present theories in explaining the high temperature oxidation mechanism of aluminum