Studies on Co-ordination Numbers of Aluminum in Aluminum Anodic Oxide Coatings

Abstract

In the preceding report, the authors discussed the co-ordination numbers of aluminum and sulfur in anodic oxide coatings of aluminum, which had been prepared from sulfo-salicylic acid or sulfuric acid electrolyte, by fluorescent X-ray method. The results suggested that the aluminum atoms in the anodic oxide coatings consist of both of 4 and 6 ligands. The dispersion in measurements of the co-ordination numbers would be due to the contamination of the test piece with aluminum metal, which had been mixed into the test piece during its folding for preparation. Therefore, this paper reports the results of determination of co-ordination numbers of aluminum atoms in various coatings by means of E.P.M.A, method. The following 8 kinds of electrolytes were used in these experiments: Sulfuric acid (for 2 kinds of test pieces), oxalic acid, chromic acid, sulfo-salicylic acid, p-phenol sulfonic acid, sodium phosphate, and ematal solution. The displacement of the K_α peak of aluminum was calculated by the following equation: Δλ=λ(aluminum metal)-λ(anodic oxide coating of aluminum) The following results were obtained: The co-ordination numbers of aluminum atoms in the anodic oxide coatings prepared from the various electrolytes were considered to be the both of 4 and 6 ligands. The above results quite agreed with those obtained by the fluorescent X-ray method and it was believed that there were no significances among the various kinds of coatings.