The present study has been made to investigate the electrodeposition of chromium from CrCl₃⋅6H₂O-HCONH₂, CrCl₃⋅6H₂O-HCON (CH₃)₂, and CrCl₃⋅6H₂O-(CH₃)₂SO solutions with additives. The solubility of CrCl₃⋅6H₂O in the organic solvents and the specific conductance of the solutions were measured, and these values were found to be generally lower than those in aqueous systems. The optimum conditions of the electrolysis in organic solvents were determined. Thin, bright and smooth deposits were obtained from the above conditions with a low cathode current efficiency (less than 30%). Chromium deposition mechanism is discussed in terms of the formation of chromium (III) complex ions in FA, DMF and DMSO solvents.

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Semi-conductive ceramic films can be produced economically and easily by thermal spraying method. The solar energy selective absorption characteristics and photoelectrolytic characteristics of ceramic films were observed. The ceramic films were composed of TiO₂, Cr₂O₃, and mixture of TiO₂ and Al₂O₃ powders. 1) Solar energy selective absorption characteristics; sprayed TiO₂ film showed below 0.1% reflectance over wave lengths of visible ray, but strong reflectance was observed above 7μm of infrared ray. Mixtured films of TiO₂ and Al₂O₃ were showed the most superior temperature ascent. 2) Photoelectrolytic characteristics; sprayed TiO₂ films on Ti substrate were obtained by argon-plasma, air-plasma and flame sprayings of TiO₂ powders. These films were heat treated in air at 800°C for 1-10 hours. The photocurrent of air plasma sprayed film electrode was greatest compared with other two specimens.

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The effects of metal ions in plating bath such as Fe, Co, Ni, Cr, Mo, W, Mn, Cu, or Sn on the properties of electrogalvanized steel sheet were investigated by corrosion resistance and paint adhesion tests. The results are summarized as follows: (1) The range of adequate current density is broader in the bath containing Fe, Co, Ni or W ions, and narrower in the bath containing Cr, Sn or Cu ions. (2) The surface appearance of plated sheet is greatly affected by the sort and quantity of metal ion in the plating bath. Plated sheet has a tendency to show fine structure, as metal ions of Fe, Co or Ni in the bath increases. In the case of containing Mo or Cr ions in the bath, it shows massive structure. (3) The effect of additive element on the corrosion resistance of plated sheet is greatly affected by the corrosion circumstances. In salt spray test, for example, plated sheet obtained from the bath containing Sn or Cr ions has more excellent corrosion resistance than the conventional zinc plated sheet. On the other hand, in the outdoor exposure test and humidity test, it has less excellent corrosion resistance. Plated sheet obtained from the bath containing Co or Ni ions has more excellent corrosion resistance than the conventional zinc plated sheet in any test. (4) Plated sheet obtained from the bath containing Co, Mo, Cr, W or Fe ions has always more excellent corrosion resistance or more excellent paint adhesion after corrosion test than the conventional zinc plated sheet, though it is greatly affected by the sorts of paints and corrosion circumstances. Among these metal ions, Co ion has the greatest effect on the corrosion resistance.

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Pulse plating of Fe-Ni alloy in a modified Watt's bath was investigated with regard to the effect of pulse conditions on partial polarization curves, current efficiency and the composition of deposit. The partial currents for deposition of iron and nickel were affected by pulse conditions independently each other. Since concentration polarization is minimized in pulse plating, hydrogen evolution was inhibited and hence the current efficiency of alloy deposition, especially that for iron deposition, was greatly improved in comparison to the d-c plating. Therefore, in order to obtain the deposit of permalloy composition (Fe: 20mass%), the concentration of ferrous ion in the bath should be reduced by the factor 1/3 of that for d-c plating. It is concluded that pulse plating yields Fe-Ni alloy deposit of a stable composition with a bright surface of fine crystal grain on an optimum pulse condition.

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Gold-tin alloys were electrodeposited in aqueous solution of K₄P₂O₇ containing KAu(CN)₂ and Sn₂P₂O₇. Cathode potential on metal electrodeposition in the mixed solution of Au⁺ and Sn²⁺ ions was intermediate between the equilibrium potentials of Au⁺ and Sn²⁺ in the bath. Gold content in gold-tin electrodeposited alloys was always higher than Au⁺ concentration in an electrolyte, and that in the coats was within the range of 78-86%, at pH9-11. Gold-tin alloys electrodeposited, whose Au/Sn mol ratio in bath was 0.03/0.25, has a dull gold-gray adhesive and smooth surface. Current efficiency of the alloy electrodeposition was close to 100% at pH9-11, and alloy coats with 20% tin content were obtained at pH8-11. Tin content of electrodeposited alloys increased with increasing current density, tending to decrease with an increase in electrolytic temperature. Cathode current efficiency was over 95% in the range between 0.22 and 0.61 of Sn/Au mol ratio of alloy composition. As a result of X-ray diffraction of gold-tin electrodeposited alloys, the crystal structure was supposed to be similar to that of metallurgical gold-tin alloys. A dully gold-gray adhesive and smooth surface was obtained under the electrolytic conditions of the Au/Sn mol ratio being 0.03/0.25, and at pH9, 25°C, and a current density of 10mA·cm^-2.

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Porous anodic oxide films formed in an oxalic acid solution were hydrated to various extents by allowing them to react with hot water at 99.5°C. The films were then dissolved in a chromic acidphosphoric acid solution and the dissolution was followed by impedance measurements in a neutral borate solution. The results were analyzed by plotting the log of the absolute value of impedance against the log of the frequency. The equivalent circuit of the hydrated film was found to consist of the capacitance of the barrier oxide layer (C_b) combined in series with a parallel combination of the capacitance and resistance components of the hydrous oxide formed in the pores (C_h and R_h). The values of C_b^-1, R_h and C_h^-1 and the their variation with the dissolution time (t_d) were determined. It was found for the films filled up with the hydrous oxide that the film-dissolution proceeds uniformly from the outside at a rate controlled by the dissolution of hydrous oxide, the dissolution rate decreases with the time of the reaction with hot water (t_h). The outermost part of the hydrous oxide formed at t_h>30min was very resistant to acid-dissolution. It was recognized that the decrease in dissolution rate is always accompanied by an increase in the specific resistance of the hydrous oxide. The barrier oxide layer next to the metal begins to dissolve at the time when the outer part of the film containing the hydrous oxide in the pores is completely dissolved. The dissolution characteristics of the barrier layer itself is little affected by the hot water treatment. These findings agree quite well with the results of a previous investigation conducted by gravimetry.

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