The effect of current interruption on the appearance of plated surface in the decorative chromium plating was investigated. The following results were obtained: (1) The cloudiness of the plated surface due to the interruption of current greatly depended on the temperature of the bath. The effect was greater when the temperature was lower, but it was less when the temperature was higher. (2) The effect of interruption was most marked at the first interruption; but became less at the subsequent interruptions. (3) The effect was considerable even if the time of the first interruption was very short; it was greater with the extension of interruption time, but became nearly stable at a certain value of time. (4) The effect was very remarkable, when chromium had been deposited before the first interruption of current. (5) The effect was greater in Sargent bath than in hydrofluosilicic acid bath.

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The effects of dipping time in chromium plating bath before the electroplating and of anodic oxidation by bipolarization during the plating were investigated. The following results were obtained: (1) When the dipping time was long or the sample was subjected to anodic oxidation in the chromium plating bath, an oxide film was formed on the nickel plating surface; then, the deposition range of chromium plating became narrower, which made it difficult to get an excellent bright chromium plating. (2) The effects of anodic oxidation were greater when the temperature of plating bath was higher and they were nearly proportional to the oxidation time; then, the deposition range of chromium plating became narrower, which finally led to very little deposits. (3) The effects of anodic oxidation were greater in Sargent bath than in hydrofluosilicic acid bath.

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The authors measured the amounts of hydrogen absorbed by a hard steel wire (0.6%C) with scale during immersion in 5, 10, and 15% of hydrochloric acid for various times. The rate of hydrogen absorption increased with the increase in descaling ratio and it reached maximum at the descaling time at which the scale was completely removed. The amount of hydrogen absorbed after complete descaling was nearly proportional to the square root of the time after the descaling. The proportion between the two factors decreased with the increase in HCl concentration. The similar relationship was obtained in the hard steel wire with no scale. It was observed by scanning electron microscopy that Fe₃C plate crystals protruded out of the steel surface after immersing in HCl. The shapes of Fe₃C plates tended to be rounded with the increase in HCl concentration. The protrusion of Fe₃C indicated that Fe₃C acted as an effective cathodic site for deposition of hydrogen and the rounded Fe₃C indicated that Fe₃C was decomposed into Fe and CH₄ by the attack of deposited hydrogen. The decrease in the amount of absorbed hydrogen with the increase in HCl concentration would be due to the decrease in effective absorbed hydrogen from the decomposition of Fe₃C.

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In order to investigate the effects of substrate temperature on grain size, surface state, and internal stress of vacuum deposited thin iron films, iron of 99.9% in purity was deposited in vacuum on an aluminum foil; the deposition rate was nearly kept constant at about 700Å/min, and the pressure was under 2×10^-5 Torr. The surface of etched thin film was observed under a scanning electron microscope and the grain size of the film was measured. The mean grain size increased from 700 to 1300Å with the rise of substrate temperature in the range from 180 to 380°C. A narrow distribution of grain size was observed at the substrate temperature of 240°C and the smoothness of the surface of the film deposited at this temperature was superior to that of any specimen deposited at any other temperature.

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A theoretical equation of the temperature difference (Δt) between electrolyte and electrode surface was derived as follows from the heat transfer theory and Joule's heat caused by electrolytic current and overvoltage:
Δt=K(iη)^0.8
and K=(0.18ν^1/4a^1/4l^1/4/λg^1/4β^1/4)^0.8, where i: current density, η: overvoltage, ν: kinematic viscosity, a: thermal diffusivity, λ: thermal conductivity, g: gravimatric acceleration, β: coefficient of cubical expansion, l: length of specimen, the results of experiments were as follows: (1) The theoretical temperature differences calculated by the above equation fairly agreed with the data obtained in the electroplating experiments: however, when gas evolution occurred on the electrode, the experimental data were lower than the theoretical values owing to the agitation effects of the gas. (2) In the electropolishing experiments, the measured temperature differences were always higher than the theoretical values. The reason for this fact would be due to the changes in physical properties of electrolyte near the electrode surface; especially, changes in viscosity and specific gravity by addition of dissolved metal ions. (3) In case of anodizing of aluminum, the following equation of temperature rise was obtained considering the heat of formation of aluminum oxide.
Δt_A1=K{i(η+2.7)}^0.8, the temperature differences calculated by the above equation was in good agreement with the experimental data.

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The authors studied on chromium deposition on the surface of 18Cr/10 Ni/Ti steel specimen in chromium diffusion coating by pack process by addition of HCl gas. The following results were obtained: (1) The calculated results at the normal temperature for chromium diffusion coating in the presence of only CrCl₂ (l), H₂ (g), and Fe (s) in the system at the early stage showed that reduction reaction was more predominant in chromium deposition than substitution reaction; and decomposition reaction occurred very little. (2) At 9000-1050°C, the diffusion coated quantity in H₂ gas nearly twice as large as that in Ar gas; but, at 1350°C, the both quantities were almost equal each other. Therefore, the cause of change in the diffusion coated quantity by treating atmosphere would be due to the presence of CrCl₂ (l). (3) Judging from the analytical results of diffusion coated layer by XMA, the percentage of chromium deposition by substitution reaction was larger with the rise of treating temperature in the chromium diffusion coating by pack process by addition of HCl in H₂ gas. However, the above percentage in Ar gas by reduction reaction was lower than that in H₂ gas treatment (4) In case of H₂ treatment at 1050°C, the diffusion coated quantity tended to increase with the increase of additional quantity of HCl gas when the quantity of HCl was small. However, the diffusion coated quantity was less in single HCl atmosphere treatment than in H₂ gas treatment.

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