Anodizing of 99.99% aluminum foil at a current density of 2A/dm² was carried out in sulfuric, oxalic, malefic-sulfuric and sulfosalicylic-sulfuric acids. Powdered oxide obtained by dissolving the anodized aluminum in Br₂-CH₃OH was subjected to differential thermal analysis, thermogravimetry and mass spectrophotometry. It was revealed that SO₄^2- anions incorporated into sulfuric acid film as much as 15.2-16.3% were decomposed to SO₂ gas at 950°C with endothermic reaction, and organic compounds in oxalic acid film, corresponding to 5.8% CO₂, were decomposed at 880°C with exothermic reaction. The structual change of the anodized films from amorphous-Al₂O₃ to γ-Al₂O₃ is thought to be accompanied by the decomposition of the anions. Although the content of SO₄^2- anions in malefic-sulfuric acid film varied with the concentration of sulfuric acid in the bath, the anions in the film were decomposed at 950°C in the same process as in the sulfuric acid film, but the organic compounds incorporated into the film were decomposed between 875 and 915°C. In sulfosalicylic-sulfuric acid film, the organic compounds derived from the sulfosalicylic acid were scarcely contained. The incorporated anions were mostly 7.5-12.1% SO₄^2-. However, the SO₄^2- anions derived from sulfosalicylic acid were found to be decomposed between 912 and 915°C, and thus the weight loss of the film seems to take place between 900 and 950°C in two steps.

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The microstructure and phase of Au-Ni alloys electrodeposited from citric acid-cyanide acidified baths were studied by utilizing T. E. M. and S. E. M. and also by measuring microhardness. The electrodeposited alloys were found to form supersaturated solid solutions on the side of Au with a limit up to about 45at. % Ni, and also on Ni side with about 95at. % or more Ni. Over the at. % range of Ni from about 45 to 95, metastable intermediate phases, which probably have similar structures to the phases of AuNi and/or AuNi₃ in metallurgically melted Au-Ni alloys, coexisted with the supersaturated solid solutions. Film growth by electrodeposition was of the following process: nucleation→island crystal→network crystal→plate crystal. Also, microcrystallites of 50-200Å in size and many microtwins were observed in the plate crystals of the films. In the initial stage of electrodeposition the film growth took place coherently with Cu substrates. The thick films deposited for 60min, on the other hand, showed smooth surfaces and the smoothness increased with increasing Ni content of the alloys. Formation of supersaturated solid solutions and metastable intermediate phases caused an increase in the film hardness. A maximum value of Hv=400 was obtained at about 80at. % Ni, but the alloys containing about 63-90 at. % Ni were brittle.

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Integral coloring of aluminum in mixture solutions of organic acids (oxalic, malonic, succinic, adipic, sulfosalicylic and tannic acids) and sulfuric acid has been investigated from V-I curves at various concentrations of these acids. Certain concentrations of organic acids and sulfuric acid having almost the same decomposition voltage, respectively, were chosen and these acids were mixed. It was found, from V-I curves, that the sum of current density in each acid mixed was equal to the current density in the mixture. The ratio of these current densities affected the color of the coatings. Dark color was obtained with increasing current density for the organic acid in the mixture. In a combination that the decomposition voltage in each acid was far different, on the other hand, the anodic oxide film was not colored as in sulfuric acid having low decomposition voltage. This was so with mixed solutions of sulfuric acid and succinic acid or adipic acid. In concentrated tannic acid solution, the electlolytic current began to flow even at an extremly low voltage and the powdered tannic acid was observed on the anode. The deposition of the powder, however, was retarded by adding sulfuric acid into the bath and the same anodized coating as in sulfuric acid was obtained. An exception was the case of electrolysis in a mixture of tannic acid and sulfuric acid, in which the above assumption that the bath composition can be determined by V-I curves was not applied.

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