Abstract:The growth of oxide film on 1100 aluminum in water was examined at 30-100°C. The initial corrosion product consisted of boehmite and thicker film of bayerite was formed on the surface at below 84°C. H...The growth of oxide film on 1100 aluminum in water was examined at 30-100°C. The initial corrosion product consisted of boehmite and thicker film of bayerite was formed on the surface at below 84°C. However, the film formed at above that critical temperature consisted of single boehmite.The rate of film formation reached a maximum at 60°C. However, bayerite was likely to be formed thicker at lower temperature.The corrosion gave rise to pitting which was caused by compound particles in aluminum and concentration cell due to dissolved oxygen in water. The pitting action was soon ended when the compound particles were separated from the substrate aluminum by dissolution of the latter. Thus, all the pits remained in microscopic size.Aluminum was colored black at below 50°C by roughness of the metallic surface due to corrosion. The coloring was not uniform and white rings developed around the pits. These rings would be formed by the change in pH brought about by the pitting action.Many fine particles consisting of secondary phase of aluminum were seen on the film formed at 60-80°C. Then, the specimen was colored brownish gray owing to these particles.Read More