This paper describes the iron eectrodeposition from a solution mainly composed of ferrous sulfate catholyte by using two compartment cells separated by an anion exchange membrane. In particular, it describes the effects of electrolyte conditions on current efficiencies for iron deposition on cathode and on efficiency of sulfuric acid generation in anolyte. There were close relations among the concentration of sulfuric acid in anolyte, pH of catholyte, efficiency of sulfuric acid generation, and efficiency of iron deposition. When the sulfuric acid concentration in the anolyte increased, the efficiency of sulfuric acid (generated in the anolyte passing through the anion exchange membrane from the catholyte) decreased, which led to lowering of the pH value of catholyte and also lowering of the iron deposition efficiency on the cathode. The current efficiency for iron deposition rapidly decreased when the pH value of ferrous sulfate catholyte was below 2.5. It was proposed to keep the sulfuric acid concentration in the anolyte at lower than 50g/l and to keep the pH value of catholyte at above 2.5 for the purpose of keeping the efficiency of sulfuric acid (generated in anolyte) higher and of keeping the efficiency of iron deposition (on cathode) higher.

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This paper describes the effects of current density on the efficiencies of iron deposition and sulfuric acid generation, and effects of catholyte conditions on carbon, sulfur, and oxygen contents of the deposit; and also relates to the voltage for electrolysis. The current efficiency for iron deposition in the catholyte of comparatively low value of pH decreased rapidly when the current density was lower than 1Amp/dm², while the current efficiency for sulfuric acid generation in the anolyte remained unchanged at a high value when the sulfuric acid concentration in the anolyte was kept at low values.
Therefore, it was possible to increase the pH value during electrolysis by employing this range of density.
Carbon and sulfur contents of the iron deposit decreased with the increase of pH value of catholyte up to about 5.2. However, oxygen content of the deposit showed a minimum value at about pH=4, except for a few special cases. The purity of iron in the deposit was over 99.9%. The oxygen liberation potential on the insoluble lead anode was equivalent to 44% of the total voltage for electrolysis; and the voltage drop due to the resistance of anion exchange membrane was equivalent to about 7% of the total voltage.

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The nucleation, growth process and structure of gold film electrodeposited on iron from aqueous solution of HAuCl₄ containing K₂CO₃ were examined by electron microscope. The results obtained were as follows: (1) The density of muclei formed at the initial stage of electrodeposition was about 2×10¹¹cm^-2. Among these nuclei, there were present pentagonal and hexagonal particles, which seemed to be multiply twinned particles. However, the ratio of these twinned particles to the total nuclei was very small. (2) The pentagonal and hexagonal particles grew up to about 400Å in size. (3) The growth process was distiuguished into the following four stages: (a) Formation of nuclei. (b) Formation of insular crystals resulting from coalescence and growth of nuclei. (c) Formation of network structure resulting from two dimensional growths of insular crystals. (d) Accomplishment of plate crystals resulting from progressing of deposition in the non-covered area. (4) The normal micro-twins were formed in the gold plate crystals during the growth process. (5) The following coherency was found between the iron substrate and gold plate crystals: (001) Fe|| (001) Au and <110> Fe|| <100> Au. (6) The addition of K₂CO₃ to aqueous solution of HAuCl₄ had an effect on the two dimensional growth of gold film; The effect increased the covering rate of substrate with gold film.

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The built-in color of aluminum anodized in oxalic acid electrolyte depended upon the wave form of the current for electrolysis. The E.S.R. spectrum of anodic oxide film at room temperature showed the presence of free spin (unpaired electron) in the films, where the spin concentration was related to the deepness of the color of the film. The pulsating current superimposed on direct current caused coloring of deep brown on the film, which is similar to the color obtained from sulfosalicylic acid bath (Kalcolor) Ultraviolet and visible ray absorption spectra of the thin film at -186°C showed several discrete absorption bands, while those at room temperature are broad and non-discrete. From these results the following three mechanisms were proposed as the causes of built-in color of anodic oxide films: (1) Inclusion of organic radicals in glassy alumina. (2) Electrons or holes trapped at the defective sites of alumina crystallites. (3) Semi-carbonized organic substances accompanied with some radicals or imperfections in the molecule.

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Effects of plating temperature and growth mechanism on reduced Ni films were studied by electron microscopy. The shape of nebulous crystals and their arrangement of crystal orientation were not changed, even if the plating temperature fell from 91 to 60°C; and they were also independent of decrease in quantity of reducing agent in the plating bath or increase in thickness of film. The growth process of reduced Ni films was as follows; in the earlier stage, small nuclear nebulous crystals deposited on the substrate by initiation treatment followed by two dimensional growth of nebulous crystals at this site, which gradually covered the whole surface of substrate. At this stage, the secondary nucleation did not occur on the other surface of the substrate. The nebulous crystals grown in two dimensions on the surface of substrate accepted Ni adatoms only in its growth direction, and these adatoms were crystallized in nebulous crystals at this site. The growth direction of nebulous crystals was independent of the crystal orientation of substrate. The increase in thickness of the plating film depended on agitation and thermal convection of the plating bath.

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