The relation between plating conditions and rate of deposition or composition of plated film was investigated in two kinds of ammoniacal alkaline electroless plating baths (A-T and A-C) for cobalt-nickel alloys of sulfate-hypophosphite system.
The results obtained were as follows.
(1) The preferable conditions for stable baths having relatively high rate of deposition and giving good appearance of plated film were as follows:
Ammoniacal alkaline tartrate bath (A-T) Ammoniacal alkaline citrate bath (A-C)
CoSO₄+NiSO₄ 0.1mol/l 0.1mol/l
NaH₂PO₂ 0.2mol/l 0.2mol/l
Na-citrate - 0.2mol/l
Na-tartrate 0.5mol/l -
(NH₄)₂SO₄ 0.5mol/l 0.5mol/l
pH(NH₄OH) 9.0 9.0
Operating temperature 90°C 90°C
(2) Under the above conditions, a desired film composition having any ratio of nickel to cobalt and containing some amount of phosphorus was obtained at a relatively high rate of deposition by controlling the ratio of concentrations of ions between nickel and cobalt in each bath.
(3) The plating rate in A-T was higher than that in A-C, but the former gave inferior appearance of deposited film to the latter owing to its lower stability. The plating rates in the both baths were higher than those in single baths (for cobalt or nickel plating) under the same conditions.
(4) The utilization efficiencies of hypophosphite in the above baths were usually kept in the range of 20-40% in A-T, and 28-30% in A-C, both of which were higher than that of nickel plating baths and lower than that of cobalt plating baths under the same plating conditions.
(5) The phosphorus content in the plated film almost linearly decreased from 2.4 to 1.9% in A-T or from 5.8 to 1.8% in A-C with the increase of cobalt content in the film.

抄録全体を表示

The composition of bath and the conditions of electroplating for Au-Cu alloys were studied.
The color of deposit containing Au, Cu, and Cd obtained from the bath was rose gold. Its composition was found to be Au=75%, Cu=18%, and Cd=7%.
The optimum composition of the bath and the conditions of electrolysis for obtaining thick deposit having excellent leveling power were as follows:
KAu(CN)₂ 7.5g/l Free KCN 15.0g/l
K₂Cu(CN)₃ 130g/l Cathodic current density 0.75A/dm²
K₂Cd(CN)₄ 0.4g/l Temperature of bath 60°C
The main wave-lenth of the deposit was measured to be 583mμ by the inspection of color tone of reflection light.

抄録全体を表示

The structure of electrodeposited Au-Cu and Au-Cu-Cd alloys was studied by means of X-ray diffraction and electron microscopy.
The results obtained were as follows.
The electrodeposits obtained from the bath containing Au and Cu (at pH=10) consisted of mixed crystals of Au and Cu throughout the whole range of any ratios between the both.
When the deposits from the bath was above 18K composition, they consisted of solid solution.
The hardness and wear resistance of the deposit was higher than those of 14K clad metal, and its corrosion resistance was superior against acids and oxidation.

抄録全体を表示

Various kinds of black chromium plating baths have hitherto been reported in literatures. However, the bath composition is not yet established in actual practice at present. Physical and chemical properties of these deposits and the mechanism of their coloration are not also thoroughly researched.
The authors examined black chromium plating baths in the literatures and found out that the bath containing hydrogen silicofluoride gave the plating with least powdery deposit and strongest adhesion; but its unevenness in color was most enormous among the platings from these kinds of baths.
Plating conditions for the most even black color were researched and the following results were obtained.
(1) The optimum composition of bath and plating conditions were as follows:
CrO₃ 300g/l Bath temperature above 10°C
H₂SiF₆ above 1g/l D_K 30-50amp./dm²
(2) Sulfuric acid should completely by removed, because its presence limited the range of black color. Hydrogen silicofluoride should be supplied to the bath according to its electrolytic comsumption.
(3) Higher throwing power was obtained by coating the substrate with copper or nickel, and then, immediately plating black chromium on that coating.

抄録全体を表示