Studies were made of the effects of nickel, zinc, and cadmium as impurities contained in cyanide baths on silver plating.
Measurements of cathodic polarization curves, absorption spectra, and electric conductivity revealed that all kinds of the three metals produced complex cyanides. The polarization of the bath containing nickel was less noble and that of zinc or cadmium was nobler than that of the originall bath.
The results of studies on electrodeposited silver by appearance, X-ray diffractiometry, and electron microscopy showed uneven brightness at lower than 0.5g/l of nickel concentration. very rough surfaces were observed by preventing the 3-dimensional nuclear growth over the whole range of nickel concentrations.
Zinc or dadmium produced more uneven brightness with the increase of its concentration at higher than 0.5g/l, when coarse crystal grains were observed.
Orientation of crystals was not observed in any of these silver platings.

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Polarization characteristics of the solution of chromic acid were examined by current-time curves determined by potentiostatic method. The following results were obtained:
1) The electrodeposition of black chromium plating gradually proceeded in the aqueous solution of single chromic acid, but the deposition was remarkably promoted by addition of a small amount of fluorides.
2) In the solution containing fluorides, the tendency to deposit black chromium plating was greater with the drop of the bath temperature and that to deposit metallic chromium plating was greater with the rise of the bath temperature.
3) In the solution containing sulfuric acid, the electrode reaction for electrodeposition of chromium was more promoted with the drop of the bath temperature.

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Densities and distributions of various elements in the crosssection of aluminum anodic oxide films were measured by electron probe micro-analyzer (EPMA).
The relation between the structure and coloring of the films was investigated with respect to the results of the above measurements.
The following conclusions were reached
1) It was found that aluminum was oxidized by oxygen by the measurements of densities and distributions of aluminum and oxygen in the films. However, these elements were not directly concerned with the coloring of the films.
2) Silicon and iron contained at radom in aluminum materials also existed in random distribution in the films.
Dark gray coloring of the films on 43 S-aluminum material prepared from sulfuric acid solution was considered to be derived from silicon in the material.
However, a thorough relation was not found between density and distribution of iron and coloring of the films in this experiment.
3) Main elements which had been contained in the electrolyte were found to be distributed in the films. These elements included were titanium, chromium, phosphorus, and sulfur. They did not adhere to the film surfaces, but would be present in the interior of the films.
The distribution of these films depended on the sort of films. The coloring of films would directly or indirectly be concerned with these elements.

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For the purpose of studying secondary hardening of anodic oxide films on aluminum, this experiment was carried out to investigate the effects of heat-and chemical treatments on hardness of the films.
The results obtained were as follows
1) The hardness of the films increased with the rise of temperature in heat treatment.
2) The rate of hardening was higher with the rise of temperature. It was found that the hardness attained to a constant value after the treatment of about 30min. at temperatures higher than 400°C.
3) The increase of hardness was remarkable when treated in boiling solutions of metallic salts. The highest hardness was obtained in the 2-stepped treatment of the combination of sodium silicate and nickel acetate.

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Chromium diffusion coatings were produced on specimens of nickel, nickel superalloys, austenitic stainless steel, and mild steel by the pack process in the hydrogen atmosphere for 10hrs. at 1100°C. The properties of the coatings such as surface roughness, microstructure, hardness, adhesion to substrate, and oxidation resistance were investigated.
The results obtained were summarized as follows.
1) The surface roughness of coatings on nickel and nickel superalloys were greater than that on steels.
2) The coatings on nickel superalloys were 70-120μ in thickness and consisted of additive layer and diffusion zone. The additive layer was characterized by the high concentration of chromium.
3) Coatings were excellent in adhesion to the substrate and were not peeled off even when they were quenched from 1000°C to room temperature in water or by hammering test.
4) Coatings were confirmed to have effective oxidation resistance in the atmosphere at high temperatures.

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The variation in the microstructure of nickel films plated from an electroless bath on iron substrates according to the change in concentration of NaBH₄ was studied by electron microscopy.
The following results were obtained.
1) The rate of deposition of nickel was lower with the decrease in concentration of NaBH₄ as reducing agent in the plating bath. Nebulous nickel crystals were precipitated as single crystalline films in the earlier stage of plating, but the films turned to polycrystals in the later stage of growth after the iron substrate had been covered with the nebulous nickel crystalline films.
2) The regular coherence between nebulous nickel crystalline films and each of iron substrate planes [(100), (110), and (111) Fe] was not observed in the deposition at either high or slow rate.
3) The nebulous nickel crystalline films were generally constituted of (112) and (101) Ni planes on various planes of iron substrate in the earlier stage of plating. The relationships between these crystals were as follows:
(112)Ni||(101)Ni
[111]Ni||[010]Ni
4) A characteristic linear streak pattern was observed in nebulous nickel crystalline films which had been plated on (100) and (110) Fe planes at slow deposition rate.

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