The corrosion behavior and corrosion resistance of electroformed nickel were investigated. The following experiments were conducted to confirm the singular feature of the corrosion of electroformed metals:
(a) Immersion test
(b) Measurement of activation energy for corrosion
(c) Measurement of polarization curve
(d) Electron microscopy
The following results were obtained.
(1) The decreasing order of degree of corrosion of nickel specimens in acidic solutions containing Cl^- was as follows: bright nickel>non-bright nickel>rolled nickel. However, the highest corrosion resistance was observed in bright nickel in HNO₃. The above facts were explained by the studies on effects of co-deposited sulfur, true surface area of specimen, and effects of Cl^-.
(2) The difference between rest potential and corrosion potential was explained from the effects of adsorbed hydrogen and adsorbed Cl^-.
(3) The values of corrosion current density calculated from the amount of corrosion corresponded well with those values obtained from the polarization curves when the true surface area of the specimen was estimated.
(4) There were three ranges in activation energies of corrosion; approximately, 1, 4-5, and 8.4-8.8Kcal/mol. These facts were interpreted by the discussion of hydrogen overvoltage, transfer coefficient, mechanism of anodic dissolution of nickel, and adsorption of Cl^-.

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The compositions of citric acid-ammonia baths for Ni-W alloy plating were studied for practical purposes as well as conditions of electrolysis, amount and component ratio of the alloy deposited.
The results obtained were as follows:
(1) The composition and amount of the alloy deposited were kept constant in a relatively wide range of variation in composition of the baths containing nickel sulfate, sodium tungstate, and citric acid, and a deposit of good quality, containing 35-40% of W, was obtained.
(2) A deposit of good quality was also obtained by the addition of ammonium citrate as a complexing agent. However, pH of the bath had to be adjusted to about 9.0 with sodium hydroxide.
(3) The addition of a small amount of hydrazine sulfate as a reducing agent was effective in the improvement of deposition efficiency.
(4) The hardness of Ni-W alloy deposit as plated was 500-600Hv. It was elevated to 900-1000Hv by the heat treatment at 500-600°C in a vacuum furnace.
(5) Ni-W alloy plating was converted into Ni-W solid solution when it was heat- treated at 500-600°C.

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Electrodeposition of metals (such as Ag, Bi, Cd, Co, Cu, Ni, Pb, Pd, Pt, and Zn) from nonaqueous DMF solutions saturated with the corresponding metal salts was investigated under steady-state current with no agitation.
Crystals having regular dendritic structure were formed in cases of Co, Ni, Pb, and Zn under current density of 10-64mAmp/cm². Whereas, less crystalline or amorphous deposits were obtained in case of Pt.
The deposits of Bi, Cd, Cu, and Pd were grown up into dendritic or mossy structure, according to the current density.
The growth of the dendritic structure was controlled by the following factors:
1. Current density and exchange current density
2. Ion concentration
3. Ionic conductivity
The leading factors for promoting the growth of dendritic structure in D.M.F. solutions were low exchange current density and low ionic conductivity.

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The throwing power of cyanide baths for silver plating was studied with respect to composition and conductance of the baths and current density-cathode potential curves; and the range of appropriate current density was studied by Hull Cell Test.
The results obtained were as follows.
The increase in silver concentration or decrease in free potassium cyanide made cathode potential more base for the deposition of silver. This fact would be due to the behavior for keeping low silver concentration by inhibiting the dissociation of complex ions. However, when the concentration of silver was 30g/l or lower, the current density was beyond the range of fine crystal deposition so that the deposit was powdered.
The addition of potassium carbonate made bath conductance higher and also made throwing power higher. However, when its concentration was 90g/l or higher, the range of appropriate current density was made narrower by the appearance of burnt deposits.
The range of bath composition for high throwing power and appropriate current density was as follows:
Ag 30-50g/l
Free KCN 40-70l
K₂CO₃ 30-60l

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