In practical treatment of wast liquor in electroplating baths with conventional equipments, it was very often evident that chemical reactions did not proceed theoretically. The case was very frequent in the disposition of cyanides. It appears that the trouble comes from the inclusion of various kinds of metallic ions in the waste liquor, which prevent noxious substances from decompotition.
The present study was carried out as follows: each kind of metallic ions was added to the waste liquor containing 10.0ppm of cyanides and chlorine was introduced into the liquor in alkaline state to determine residual cyanides content.
As the results of the above experiment, it was found that Fe and Ni ions remarkably prevented chlorination of alkaline waste, while single inclusion of Zn, Cu Cd, or Cr ion gave no substantial effects.

View full abstract

It has been well known that the corrosion resistance of electroless nickel plating film by acid plating solution is superior to that of electroplated nickel film by Watt's bath. Effects of pH of plating solution, sort of nickel salt used, and kind of acid for dipping solution on the corrosion resistance of electroless nickel plating film were studied; in which the last effects were investigated by electrolytic polarization method, Ferroxyl tests, salt spray test, and outdoor exposure test. The following results were obtained.
1) The results of nickel sulfate were better than those of nickel chloride for the constituent of electroless nickel plating solution.
2) The decreasing order of corrosion resistance of plating film with plating solution was as follows; acid>ammoniacal>alkaline. However, the order with outdoor exposure tests was not the same as above.
3) When plating film was relatively thin, hydrochloric acid was not suitable for the pretreatment of steel substrate: while, when it was thick, there were almost no effects of the acid on its corrosion resistance.

View full abstract

The optimum composition of electrolyte and operating conditions for electrodeposition of magnetic thin film of Fe-Ni alloy (Fe/Ni=20/80) were determined in the previous paper.
In the present paper, the cathodic potential, including the internal resistivity of cathode wire (0.2mm∅) itself, and the cell voltage balance are discussed by means of analytical measurements of each factor contributing to the total cell voltage. It was observed that some unreasonable defects were especially caused by concentrated current density in the range of continuous flow system shown in Fig. 1.

View full abstract

The plating of indium-tin alloy was studied by means of cathode potential-current density and practical plating experiments. The effects of the factors on compositions of deposited alloys were discussed.
Excellent results were obtained by using Sn⁺⁺⁺⁺ or Sn⁺⁺⁺ acidic bath and alkaline bath, both of which containing carboxylic salts, and optimum conditions were determined.
The alkaline bath was superior to the acidic bath on the stability and control of the plating process.

View full abstract

The film formation and blackening discoloration of pure aluminum in boiling solution were examined by the following process.
The amount of film in the solution (pH 3-10) increased proportionally to the logarithm of exposure time. In acidic solution, the amount tended to minimum toward pH 4, while in sodium hydroxide solution the film became thicker.
Discoloration in acidic solution (pH 2.5-3.5) was caused by the corrosion and roughness of metallic surface. While, in neutral or alkaline solution (pH 4-10) it was caused by the adsorption of silica onto the surface film.
Colorless surface film revealed dark corrosion product in itself which had been formed by preferential attack of particles in secondary phase of aluminum. However, its amount was not so large as to be the discoloration of surface film.

View full abstract