The recovery of chromate ions from dilute solutions in low voltage electrolysis has been investigated in relation to the effects of diaphragm components and applied voltages. Mixtures of SiO₂ and Al₂O₃ powders and several kinds of porous refractory tubes were used as diaphragm materials. A netlike cathode was used in close contact with the diaphragm in order to remove the chromate ions quickly out of the cathode solution as they were formed. The chromate concentration in the cathode solution decreased logarithmically to the lower limit when the voltage of more than 6 volts was applied. The chromate ion elimination rates increased parabolically in the range of 6-20 volts but were not affected appreciably by the voltage more than 20 volts. The rates were independent of the diaphragm component in the Al₂O₃ range of 0-60% but decreased with increasing ratio of more than 60% Al₂O₃. The lower limit of chromate concentration was less than 3ppm for diaphragms consisting of less than 60% Al₂O₃ and increased with increasing Al₂O₃ content of more than 60%. Chromate ions can be thus recovered electrolytically from dilute solutions in a short time by use of the diaphragm containg more than 40% SiO₂ and in the range of 20-30 volts.

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Titanium films of 0.5-10μm in thickness were ion-plated on mild steel substrates under various plating conditions using a diode system with electron beam-heated source materials. The surface morphology, hardness and porosity of the coatings were examined as functions of argon pressure (2×10^-5-1×10^-2 Torr) and of negative bias voltage to the substrate (0- -4kV). The low pressure process below 2×10^-4 Torr provided the coatings with good properties, that is, the fine, dense structure, the improvement of brightness, and a decrease in porosity. The use of higher bias voltages resulted in a decrease in porosity and the grain refinement of the coatings. The corrosion potential of the titanium coatings above 2.5μm in thickness was almost the same with that of pure titanium sheet in 3% NaCl aqueous solution, and thus the satisfactory corrosion resistance was confirmed. The ion-plated titanium coatings showed far more excellent adhesion to the steel substrates than the coatings obtained by conventional vacuum vapor deposition.

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Electrolytic coloring was investigated in the bath containing nickel (II) sulfate, tin (II) sulfate or their mixture by using DC and AC sources. Vertical distribution of the deposited metal in the pores was determined by an electron probe microanalyzer (EPMA). The anodized films were colored in black in all cases and the color tone was depending upon its thickness. Tin was more deposited than nickel in the pores when the same electrolysis duration was used. Deposited nickel and tin were foundto bo located near the pore bottoms and branched pores were observed in the cross sectional figures of the anodized film. It was suggested that the black color of the anodized film was depending not upon the amount of deposited but upon the anodized film structure.

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Influence of temperature on the passivation of zinc in a concentrated alkaline zincate solution has been studied using stationary and rotating disk electrode techniques. Passivation time increased as the bath temperature increased reaching a maximum at 45-55°C. Effect of rotation was larger at higher temperatures than at low temperatures. Limiting current density and value of constant K changed at 40-45°C. It was found that the dissolution process of zinc was kinetic-controlled in the low temperature range and was diffusion-controlled in the high temperature range. A gray film was formed on the anode at low temperatures, the color of which varied to blue, brown and white at temperatures above 40°C. The apparent activation energies for the formation of a passivated film onzinc anode were 3.80Kcal/mol and 2.19Kcal/mol in the bath temperature range of 15-45°C and 45-65°C respectively. From the results obtained, it could be seen that the anodic reaction of zinc changed radically when the solution temperature reached 50°C.

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In electrodialysis for desalting of primarily treated waste solutions in plating and degreasing processes, the ion exchange membranes used may be fouled by the organic compounds contained in the solutions. The fouling of the ion exchange membranes was examined, therefore, by using a small test electrodialysis cell. Strong organic acids (M. W. more than ca. 300) and strong organic bases (M. W. more than ca. 350) significantly fouled the anion and cation exchange membranes, respectively. The membranes, however, were little fouled by weak acidic, basic or neutral organic compounds. The extent of fouling depended on the concentration of the organic compounds.

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For the purpose of obtaining a high hardness coating, a steel plate surface spread uniformly with TiC powder is molten by the electron bombardment. The powder, which is white heated by the bombardment but still in solid state, precipitates into the molten surface layer. The TiC-containing steel surface thus formed has a high hardness number of Hv 2700-5400. Optical and electron microscopic investigations of a section of the high hardness coatings show that the TiC particles are wetted by steel, and the coating adheres strongly to the substrate by the wedge effect. It was also found that neither minute holes nor bubbles are detected. This TiC-coated steel can be used as a high hardness, heat-resistance and wear-resistance material.

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