The current efficiency for chromium plating from low concentration CrO₃ baths was measured and the following results were obtained.
(1) The highest current efficiency of 22% was obtained in a chromium plating bath of CrO₃ 50g/l at 50Amp/dm² and 55°C containing H₂SO₄ 0.6-1.5g/l and Na₂SiF₆ 1.0g/l as catalyzers.
(2) However, the above bath composition did not correspond with the composition for highest brightness and covering power.
(3) The current efficiency of the low concentration chromium bath containing CrO₃ 50g/l, H₂SO₄ 0.5g/l, and Na₂ SiF₆ 0.5g/l was between that of Sargent Bath and that of fluorosilicate bath under various plating conditions.

抄録全体を表示

Various compositions of tin-zinc alloy deposits were obtained from tetrafluoroborate baths. The corrosion resistance and solderbility of these deposits were studied and the following results were obtained:
(1) The deposit on steel substrate containing about 80% of Sn, which had been obtained from the bath containing a brightener, had the highest corrosion resistance; and the same deposit of 10μ in thickness, which had been treated with choromate solution, did not tend to rust after 3000-4000hrs. of continuous salt spray test.
(2) The alloy deposit on steel or copper plating substrate containing about 60-80% of Sn, which had been obtained from the same bath, had the highest solderbility; and the same deposit treated with chromate solution had a slightly less solderbility.
(3) The composition of these alloy deposits from these baths depended upon the ratio of metallic ion concentrations between the components and concentration of tetrafluoroboric acid in the bath and current density. However, there was not a great change in the composition when the deposits had been obtained from a bath containing 70-80% of Sn in which the concentration of tetrafluoroboric acid and current density were kept constant. Accordingly, it was known that the alloy deposits containing about 80% of Sn and having highest corrosion resistance and solderbility were obtained from the above bath.

抄録全体を表示

Reduced Nickel plating films were obtained on copper substrate from the electroless plating baths containing 200mg/l and 50mg/l of NaBH₄ as reducing agent.
The films were observed under an electron microscope and the following results were obtained:
(1) The nickel plating films consisted of nebulous crystals, which were observed in the state of aggregated very fine microcrystals.
(2) The nebulous crystals, which had been obtained from the electroless plating bath containing 200mg/l of NaBH₄, consisted of microcrystals of under 500Å in size, and had faint orientations. The orientations gradually disappeared with the increase in thickness of plating nickel films.
(3) When the concentration of reducing agent (NaBH₄) decreased to 50mg/l, the plating rate became slower and fine microcrystals were arranged in several orientations.
(4) Microcrystal grains of about 100Å in size were observed in the nebulous crystals which had been obtained from the bath containing smaller amount of reducing agent.

抄録全体を表示

This paper describes integrally colored films which have been prepared by electrolytic coloring simultaneously with anodizing in aqueous solutions of ammonium hydroxide and ethylenediamine containing ammonium fluoride and metallic salts.
When specimens were electrolyzed by AC in ammonium hydroxide bath [containing NH₄OH 2.3mol, NH₄F 0.27mol, NH₄-tartrate 0.1mol, (NH₄)₂CO₃ 0.1mol, and Ni (Fe and Sb) salt 0.02mol] for 30min. under current density of 2Amp/dm², a black or brown colored film(about 5μ in thickness) was obtained.
The corrosion resistance of this film was higher than that of the anodized film in H₂SO₄, and its hardness decreassed by sealing with boiling water.
On the other hand, when ethylenediamine solution [containing (NH₂CH₂)₂ 0.5-1%, NH₄F 0.27mol, NH₄-tartrate 0.05-0.3mol, (NH₄)₂CO₃ 0.05-0.2mol and Ni (Co, Sb, Fe, Ag, Cd, Zn, and Cu) salt 0.02mol] was used as an electrolyte under the same conditions of the above electrolysis, the following films were obtained:
a black film for Ni and Sb salts
a brown film for Fe, Zn, Co, and Cd salts
a yellow film for Ag salt
and a green film for Cu salt
The hardnesses and corrosion resistances of the colored films decreased and their colors faded after sealing with boiling water.

抄録全体を表示

The primary requirements for galvanic anode are electrode potential sufficiently electronegative for providing an adequate current, a high electric output per unit of anode consumed, and a low cost of metal.
Aluminum has theoretically less noble electrode potential and very high output for providing current. Accordingly, its profit in cost is twice as large as that of another metal such as zinc or magnesium. However, pure aluminum has not yet been used in practice for galvanic anode, becaues of the formation of protective oxide film, which limits its actual dissolution potential to about -0.7V (S. C. E) in artificial sea water.
Therefore, electrochemical properties of aluminum in aqueous solutions of sodium chloride, sodium sulfate, and their mixture were measured by means of a potentiostat.
The results obtained were as follow
(1) The pitting potential of aluminum (99.99%) in 0.5N sodium chloride solution was -0.7- -0.76V (S. C. E).
(2) Inhibition effect of SO₄^2-ion on pitting corrosion of aluminum in chloride solutions was not remarkable.
(3) The purity of aluminum had effects on the spontaneous electrode potential and pitting potential.

抄録全体を表示

In order to investigate whether Al-Ga alloys can be used as a galvanic anode for cathodic protection, discussion of anodic polarization curves and galvanic anode tests were conducted in a neutral solution containing NaCl and Na₂SO₄.
The results obtained were as follows;
(1) Pitting potential was observed on the anodic polarization curves of Al alloys in the solutions containing Cl^-. The Al alloys were abruptly activated at a potential approximate to the above pitting potential and the increase of anode current was observed.
(2) As for the effect of additional gallium on the pitting potential, the potential became less noble with the increase in the amount of additional gallium.
(3) The pitting potential became nobler when the purity of Al in the alloy was higher.
(4) The pitting potential became slightly nobler with the increase in the concentration of SO₄^2-.
(5) The uniform corrosion of Al-Ga binary alloys could not be obtained by the addition of gallium.
(6) The results of galvanic anode tests revealed that the current efficiency tended to decrease with the increase in the amount of additional metal.
(7) The spontaneous electrode potential of Al-Ga binary alloys became less noble with the increase in the amount of additional alloying element, gallium.

抄録全体を表示

In order to explain the activation process of Al-In alloys dipped in a neutral solution containing NaCl, electrochemical properties and corrosion aspects of In were discussed by conducting galvanic anode tests.
The results obtained were as follows:
(1) In was dissolved in both of Cl^- and SO₄^2-solutions. The dissolution mechanism greatly depended upon pH value near the anode.
(2) The uniform corrosion of binary Al-In alloys could not be obtained by the addition of in the rangeof experiments.
(3) The current efficiency of Al-In alloys had a trend to decrease with the increase in addition of the alloying element, In.
(4) The anode potential became less noble with the increase in addition of the alloying element, In.
(5) The pitting potential also became less noble with the increase in addition of In.
(6) The current efficiency of Al-In alloy was higher and the pitting potential was nobler when the purity of Al in the alloy was higher.

抄録全体を表示

The adsorption behavior of a trace of copper as impurity in cyanide baths for silver plating was studied by means of a radioactive tracer. The authors selected ⁶⁴CuCN as a labelled compound and added it in the cyanide baths for silver plating.
The following results were obtained for the adsorption behavior of copper on the cathode surface in electrode reaction process:
(1) The adsorption of copper in stationary baths increased with the increase in copper concentration.
(2) The adsorption abruptly increased at a current density of 2A/dm², and it was about 100 times as lage as that of at 1.5A/dm².
(3) The adsorption increased with the rise in bath temperature.
(4) The adsorption occurred within the thickness of about 8000Å of the electrodeposited silver; accordingly, it was not occlusion in the electrodeposited silver, nor incorporation with the crystal structure.

抄録全体を表示

The preferred orientation, grain size, and visual appearance of chromium electrodeposited at 30-70°C and under current density of 20-60Amp/dm² of smoothed D. C were studied. The bath composition was as follows:
CrO₃ 250g/l
and H₂SO₄ 2.5
The determination of preferred orientation was conducted by X-ray pole figure method.
The following results were obtained
(1) The brightest deposits obtained at 40 and 50°C were characterized by a high preferred orientation of ‹111›, and they less depended on the current density rather than on the temperature.
(2) A very close correlation was established between the brightness and grain size.

抄録全体を表示