On the oxidation of Zirconium by heat tinting

The early stages of the oxidation of iodide zirconium in the temperature range 673–823 K were studied using the heat tinting technique. An activation energy of 128 kJ/mol was calculated. Anisotropy of the oxidation is significant and depends on the preferred orientation of the grains. Twins have indicated the anisotropic nature of the oxidation process by showing different color contrasts. It was found that the increase in the thickness of the oxide film takes place by the nucleation and growth mechanism. This process was noted to be extremely dependent on the orientation of the grains. Preferential oxidation of the bulk of the grains was observed and substructure formation could be easily identified.