There was aging of lacquering property in electroplated tin plates.
When a sheet of tin plate was exposed in the atmosphere of ordinary humidity at room temperature, the lacquering property gradually tended toward the worst state, and then tended back toward better state. This tendency was accelerated by heating in the air as described in the 1st report. However, when piled tin plates were exposed under the above conditions, the result was sowewhat different-the lacquering property also arrived to the worst state, but it remained stationarily at the state for a long period.
Oxygen atmosphere gave good effects, but nitrogen or humid atmosphere gave no good effects on aging of lacquering property.
Discussions were presented on the cause of lacquer dewetting, considering the results of these experiments. It was concluded that the deterioration of oil film on tin plate was not an important factor.

View full abstract

Many industrial merits are found in electro-chemical machining of metals as compared with other conventional methods of metal working though the accuracy of the worked piece by electro- chemical machining is not very satisfactory.
The author investigated anodic dissolution, working condition, and workability of removing iron in electro-chemical machining and the following experimental results were obtained:
(1) Electro-chemical machining of iron could be successfully performed when halogen compounds were used for electrolyte.
(2) The accuracy of worked piece was variant depending on distance between electrodes, nature of electrolyte and chemical composition and microstructure of working material.
Electro-chemical machining of irons of almost same composition in sodium chloride solution gave variable results of anodic polarization potential depending upon the microstructure of working material.
When anodic polarization potential was lower, both current efficiency and penetration rate were higher and also the removing was more effective.

View full abstract

In the previous paper, the author reported the study on electro-chemical machining of iron from the electro-chemical standpoint. In this paper, discussions were made over various factors affecting workability of removing iron such as pH of electrolyte, evolution of chlorine gas, and formation of reaction product in sodium chloride solution. The following experimental results were obtained.
(1) The solution was always alkaline when sodium chloride was used for electrolyte.
(2) Chlorine gas was not detected by potassium iodide-starch paper test during the electrolysis.
(3) Precipitate in the electrolyte was mainly composed of very fine powders of magnetite (Fe₃O₄).

View full abstract

Copper-alumina or silver-alumina alloy layer was electrodeposited in suspension consisting of electroplating solution and alumina powders.
The effects of concentration of powders in plating solution and current density given on alumina content of deposited alloys were studied. Microstructure and hardness of deposited alloys after annealing were also studied.
Hardness of electro-deposited copper-alumina or silver-alumina alloys both in deposited and annealed state was higher than that of electro-deposited pure copper or silver. For instance, copper -6.5vol. % alumina alloys showed hardness of 86 (V. H. N.) after being annealed at 800°C for 30 minutes, while pure copper showed 49 after the same treatment. Microstructures of copper-6.5vol. % alumina and silver-10.7vol. % showed almost no grain growth after annealing at 800°C and 600°C, respectively.
It was observed under electron microscope that the distribution of alumina phase in deposited alloys was uniform.
It may be concluded from the above facts that high hardness and fine grains of deposited alloys after annealing are due to alumina phase dispersed in matrix.

View full abstract