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.

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The oxide films formed on aluminum in acids were investigated by means of the apparatus consisting of a potentiostat and a high sensitive recorder.
The results obtained were summarized as follows:
1) When the set potential was maintained at-0.3V vs. S.C.E. in sulfuric acid, two straight lines having different slopes were obtained in the following two periods; from O to 1.5 and from 1.5 to 12sec. The above facts suggested the formation of oxide films by ionic conduction and the film obtained in the latter period was considerably more compact than that in the former period.
2) When the set potential was OV, the formation of oxide film by ionic conduction was continued for 6sec.
The oxide film was soon converted into a compart insulating film and the anode current was increased with the lapse of time, which represented that the dissolution of the oxide film took place.
3) When the set potential was above OV, an electrochemical process virtually similar to 2) was observed.
4) In hydrochloric acid, the anode current rapidly flowed at a potential higher than spontaneous electrode potential.
When hydrochloric acid was used as an electrolyte, the film was not formed at all and aluminum seemed to be dissolved in proportion to the passing of anode current. As for the corrosion, pits were produced over the whole surface.

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Investigations were made concerning the electroplating of copper on pure (2S) and impure (61S) aluminum anodized in H₃PO₄ or H₂SO₄ and the anodic oxide films were studied with respect to the deposition mechanism of metals on anodized aluminum.
(1) When aluminum bases were anodized in H₃PO₄ baths, smooth copper deposits of 100% coverage were obtained for 61S-Al, but never for 2S-Al.
(2) In H₂SO₄ anodizing, 100% coverage was achieved for both of 61S-Al and 2S-Al only when the oxide films were relatively thin (<3μ).
(3) The X-ray diffraction and infrared absorption spectrum of the oxide films revealed no differences in crystallographic and mechanical structures between H₃PO₄ and H₂SO₄ anodizing for each of 2S and 61S oxide films.
(4) The current-time curves during the potentiostatic cathodic polarization of anodized aluminum specimens suggested that the oxide film formed in H₃PO₄ was stronger and more adhesive than that formed in H₂SO₄, and electric conductivity of films was believed to be constant.
(5) It was also suggested that some impurities in aluminum base remained in the oxide film formed in H₃PO₄ and acted to form nuclei in the subsequent plating process.

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Studies were made on anodic behavior of each or together of zinc and iron in various kinds of alkaline zinc plating baths.
The results obtained were as follows:
1) The polarization of zinc anode was decreased with the decrease in concentration of OH or CN ions and was increased with the increase in concentration of Zn ions in plating baths.
2) In activated state, anodic current efficiency of zinc was 100%. A film corresponding to Zn(OH)₂ grew at the potential between critical passivity and Flade; and a film corresponding to ZnO grew at the potential for retaining passivity. The anodic current efficiency of zinc was decreased under these conditions. However, the current efficiency for zinc both contained in the films and dissolved was about 100%.
3) When both of zinc and iron were used together for anode, only anodic behavior of zinc was indicated at the initial stage; and then, the bath was led to potential for generating oxygen from iron when the current passed through the critical passivity of current density of zinc. At this stage, zinc anode was electrolyzed at the potential for retaining passivity.
The problems mentioned above are important in controlling of anode and plating bath in practice of alkaline zinc plating.

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Various compositions of cadmium-tin alloy electrodeposits were obtained from tetrafluoboric acid salt baths, to which several kinds of addition agents had been added.
The compositions of these alloys depended upon bath composition, temperature, current density, and the condition of stirring.
No red rust spots appeared on the cadmium-tin alloy deposits containing about 95% of cadmium, which had been electrodeposited on iron base. It was confirmed by salt spray test, CASS test, and exposure test that the same composition alloy had the highest corrosion resistance.
In comparison between corrosion resistances of alloy electrodeposits of about 10μ in thickness and zinc or cadmium deposits having the same thickness, it was proved by all the corrosion tests that the former had the highest corrosion resistance.

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