Ni-Mo deposits were obtained from ammoniacal tartrate baths containing various amounts of molybdate and Ni ions. The partial current efficiency of Mo deposition increased gradually with increasing Mo content of the deposits and then decreased to zero after a maximum was achieved. X-ray photoelectron spectra of Mo3d and Ni2p3/2 levels for the deposits showed that these elements existed in a metallic state before a maximum partial current efficiency of Mo deposition was achieved. When the Mo content became higher than the one at a maximum partial current efficiency of Mo deposition, high valency Mo compounds were also detected. At the limit where the efficiency of Mo deposition decreased to nearly zero, the spectra of the deposits agreed with those of low valency Mo oxides. From these results, the step-wise reduction mechanism of molybdate ion was verified in the induced codeposition of Mo with Ni.

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Pulse plating of tin in an acidic stannous sulfate bath without the presence of additives was studied with regards to the polarization curve, current efficiency, and the morphology of deposit. The polarization curves exhibit a well-defined Tafel line with a slope of 54-67mV/decade at high current densities. The minimum current density, where the Tafel relation holds, increased with decreasing pulse ratio (on-time/off-time). On the other hand, current efficiency decreased with decreasing pulse ratio, mainly because of the charging of the double layer. The deposits plated with long pulse time or direct current were of either needle-type or dendrite. Smooth deposits were obtained at the conditions of short pulse time and high current density. The conditions for obtaining the smooth tin deposits of fine grains were discussed in terms of current density and pulse time.

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Electropainting of steel reed was carried out using a potentiostat (potential range ±100 Volts, ±1A), and mechanical vibration energy (M. V. Energy) absorption of the steel reed during electropainting in 10% acrylic paint solution was measured to clarify the electropainting mechanisum. M. V. Energy absorption was observed only at paint deposition stage. It indicates the existence of network structure layer of resin flocs outside the deposited paint film, and the structure of the layer is also elucidated from the frequency dependency of M. V. Energy absorption at paint deposition stage.

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The polarization behavior of cobalt in electroless cobalt plating baths has been studied by using DEAB, NaH₂PO₂ or NaBH₄ as reducing agent respectively. Polarization experiments, based on the mixed potential theory, were also made on the baths without the presence of either metallic ion or reducing agents so that to simulate the partial polarization curves. The rate of electroless cobalt plating decreased in the order of DEAB, NaH₂PO₂ and NaBH₄. The electroless plating potential for each system shifted to noble direction in the same order. It was found from the polarization curves that the rate of electroless cobalt plating increased with increasing concentration of DEAB but was not sensitive to Co²⁺ concentration. On the other hand, in the baths containing NaH₂PO₂, the rate depended on the concentrations of either NaH₂PO₂ or Co²⁺. The polarization curves, obtained by superposing the partial anodic and cathodic polarization curves, were not well consistent with those obtained in the complete plating baths. It is likely that the partial anodic reactions were affected by the presence of Co²⁺ or cathodic reaction probably because of the change in pH at the interface and the formation of cobalt oxides, whereas the partial cathodic reaction was independent of anodic reaction. The measurement of the polarization resistance was made in the electroless plating baths. As was reported in the previous paper, the rate of electroless plating i_p1 is related to the polarization resistance Rp, thus i_p1=K/Rp where K is a constant. The present results also obeyed this relationship with the K value of 0.091. It is concluded that the instantaneous rate of electroless cobalt plating in the citrate bath containing DEAB can be also monitored by the polarization resistance method.

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The structure of hydrated chromium oxide on Tin Free Steel (TFS) formed in a low concentration CrO₃ bath containing a small amount of fluoride, silicofluoride or sulfate was investigated by XPS. Lacquer adhesion before and after immersing in a hot citric acid solution was also examined. The lacquer adhesion of TFS was discussed based on the structure of hydrated chromium oxide. The results obtained were as follows: 1) The hydrated chromium oxide films on TFS basically consisted of polymerized chromium (III) hydroxide, in which a part of OH ions was replaced by fluoride ions or sulfate ions. In the case of silicofluoride bath, silicon was not incorporated into the film. 2) When the films formed in the fluoride baths were heated at a lacquer curing temperature, both the oxolation of hydrated chromium oxide and the removal of incorporated fluorine occurred. On the other hand, in the case of the film formed in the sulfate bath, incorporated sulfate ions were kept in the film after heating, and the oxolation of hydrated chromium oxide occurred slightly. 3) After immersing in a hot citric acid solution, TFS formed in the fluoride baths showed much better lacquer adhesion than TFS formed in the sulfate bath. This was explained by considering larger amount of hydroxyl ions in the films formed in the fluoride baths, when assuming that the adhesion is supported by hydrogen bonding between the hydroxyl ions and the lacquer. 4) After immersion in a hot citric acid solution TFS heated before lacquer coating showed lower adhesive force than TFS without heating because of the slight oxolation of hydroxyl bridges in films on TFS.

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