When titanium is polarized anodically in 0.5N NaCl solution, anodic current due to evolution of oxygen rose rapidly and reached a maximum value over the potential range+1.8 to+1.9V (vs. SCE). The peak of the current disappeared almost completely by scanning potential toward cathode. The results, which were obtained through the effects of pH of the electrolyte and of pre-treatment on anodic polarization curves in 0.5N Na₂SO₄ and in 0.5N NaCl solutions, show that lattice defects in oxide films on Ti surface may cause the peak of the anodic current mentioned above. The pitting potential of Ti in 0.5N NaCl solution was loud to depend on the pre-treatments. Pitting corrosion occurred at 8-9V on the emery polished surface and at about 12.8V on the chemically polished surface.

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Solution of sodium hydroxide, sodium carbonate and sodium hydrogen carbonate was added to the nickel sulfate solution, and residual nickel concentration as well as pH value in the filtrate was examined. Properties of precipitate related to sedimentation, filtration and washing were also investigated. In the case of using sodium hydroxide as precipitant, colloidal precipitate was formed, which could be readily settled and filtered when suitable amount of coagulant solution was added. But there may be some difficulties at post-treatment or reutilization of such bulky sludges. On the other hand, using sodium hydrogen carbonate, dense powdery precipitate was obtained. Residual nickel concentration in the filtrate was found to be sufficiently low, as enough heating or aeration was applied.

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Effects of organic carboyl compounds on brightening and electrochemical behavior were studied in the electrodeposion of tin from acid sulfate bath. Electrochemical polarization measurements, potential sweep voltammetry and scanning microscopy were applied. Among the compounds examined, benzalacetone was the best additive for the brightener, and its adsorption on electrode in an acidic solution was ascertained through cyclic voltammetry.

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Effects of various additives on the high-speed electroless copper deposition from EDTA bath were investigated. By electron-microscopic observation of the surface of copper deposit from the additive free EDTA bath, it was shown that the surface consisted of fine and easily fallen off particles that would cause spontaneous decomposition of the bath when they fell off into the solution. Single use of ferrocyanide, potassium nickel cyanide, or sodium nitroprusside as additive in EDTA bath improved the ductility of the copper deposits to some extent, and the deposits from these baths provided the surface consisting of small pyramidal crystals at 50°C, which grew to larger and more leveled grains at 70°C. As previously reported, the authors found that the ductility of copper deposit was remarkably improved when 2, 2'-dipyridyl and the other compound, e.g. potassium nickel cyanide, were added together into the EDTA bath. Electron-micrographs of copper deposits from these baths contaning two additives provided the surfaces apparently more leveled than those from the baths containing each additive individually. Thus the corelation between ductility and surface leveling was confirmed. Ductility of copper deposit and deposition rate increased with increasing bath temperature up to 80°C, beyond the temperature deposition rate decreased because of the predominance of Cannizzaro reaction. Further addition of some kinds of nonion type surface active agents into the plating bath was found to give favorable effects on the ductility of the deposit.

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