To obtain high corrosion resistant cobalt platings, Va group semi-metal ions were added to the citrate electroplating bath. The composition, appearance, and corrosion resistance of the deposits were determined. The molar ratios of the amounts of semi-metals co-deposited to those in the plating solution were 2 for As and 4 for Bi and Sb. These semi-metals were excellent brightners for cobalt plating; the effectiveness of the additive elements on the appearance was in the order of Bi>>Sb>As, and on the tarnish resistance Sb>>As>Bi. The corrosion resistance in salt spray test was improved about 5 times by introducing the semi-metal elements. Reproducible data indicating high corrosion resistance were obtained in concentrations of 2×10^-3mol/dm³ for As and 4×10^-3mol/dm³ for Sb and Bi. The deposits obtained in these concentrations provided the most suitable appearance. In the addition of small amounts of semi-metals such as 10^-4mol/dm³, As was the most effective element on corrosion resistance, Sb was also effective but Bi was not. Addition of more amount than the above mentioned concentration such as 10^-2mol/dm³, produced brittle, rough or dark colored deposits.

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Hull Cell is an experimental plating cell in which a cathode is obliquely arranged to an anode, and the plating with wide range of electrical current densities can be tested by only once electrodeposition. The cell is therefore widely used for decision of plating condition, make-up of bath compositions and control of plating bath. But it is difficult to calculate theoretically and correctly the current densities on arbitrary points on a cathode. So, generally some approximate experimental formulas have been used. In this report, the authors suggest a concentric cell instead of the Hull Cell, and it was named Tena Cell. Current densities on optional points of cathode can be precisely and simply calculated in this cell. Moreover, the cell can be used like a Harling Cell being arranged two cathodes to both side of an anode. Electroplating has been studied on two cathodes that are divided into five equal parts each. In this study, we used copper (II) sulfate and copper (II) borofluoride solutions for plating baths. Experimental results are nearly coincide with theoretical values. As a result, we propose the Tena Cell as a more simple and precise cell than the Hull Cell.

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Electrodeposited Cu-Co alloys and Co from pyrophosphate baths were investigated by electron microscopy. Electron diffraction analyses revealed that the electrodeposited Cu-Co alloys formed a super saturated solid solution β(M), a Co rich h.c.p. solid solution ε′_E.D., and a Co rich f.c.c. solid solution α(M) at the cobalt concentrations of about 31 at.% or less, about 40-99 at.% and about 72-99 at.%, respectively. Consequently it was clear that these electrodeposited alloys differ from those in the equilibrium diagram. (β(M), α(M) and ε′_E.D. correspond to β, α and, ε′ in the equilibrium diagram; hence, suffix (M) indicates the metastable phase and E.D. the electrodeposit.) The lattice parameters of β(M), α(M), and ε′_E.D. were a≅3.60-3.62Å, a≅3.56-3.58Å and a≅2.51-2.54Å, c≅4.10-4.15Å, respectively. TEM observations revealed that the growth of these electrodeposited alloy films took place in the nucleation and growth process, and also, the deposits grew up to the plate-crystals consisting of finer crystallites of several hundred Å in size and containing many microtwins and fibrous crystals. SEM observations showed the alloy films became increasingly fine and smooth with an increase in Co content. Further, by the TEM observation it was found that the pseudomorphic growth took place in the about 50Å thick electrodeposited Co film on Cu substrate.

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It was found that the adsorption amount of zinc ions from Watts type nickel plating solution on the weakly basic anion exchange resin (Sumichelate CR-2) increased by about 10 times as compared to that on strongly basic anion exchange resins. Therefore, ion exchange equilibrium constants of Sumichelate CR-2 for ZnCl₄^2- and HZnCl₄^- were measured in the mixed solution of HCl and LiCl containing 10mol/l Cl^-. The constants obtained for ZnCl₄^2- and HZnCl₄^- were 1.5×10⁵ and 3.1×10⁴ respectively, and these values were 3 times as much as those of the strongly basic anion exchange resin (Dowex 1-x8) for the same anions. No different ratio of ZnCl₄^2- to HZnCl₄^- was obtained, however, in bath case of Sumichelate CR-2 and Dowex 1-x8.

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