Recently, the permanent mold process has been employed for producing iron castings on a large scale because of its economic and technical advantages. The short service life of the cast iron molds, however, hinders the development of the process. In general, the same kind of material is used in iron castings as in metal mold material. This prevents cracks in the castings due to differences of expansion and contraction coefficients between the metal mold and the castings during solidification and cooling. However, the cast iron metal molds are themselves destroyed by cracks which are caused by thermal effects. Diffusion impregnating is one means of preventing destruction of the metal mold. The author discovered that cast iron siliconized by the powder method using Fe-Si-Cr alloy with high purity did not have such defects as rough surface and a porous layer: a layer obtained by using Fe-Si-Cr alloy powder containing 20-30% Si and 30-40% Cr and by heating at 1, 100° in H₂ for 4-10 hours had about 9% Si and about 2% Cr, and 30-80 microns in thickness. Chromium in the alloy powder reduces the diffusion rate of silicon in the Fe-Si layer. The applicability of the siliconized cast iron as a new metal mold material was studied by examining oxidation and thermal shock resistances, thermal stability, microhardness at elevated temperatures etc. The siliconized cast iron is superior as a new metal mold material and siliconizing extends not only mold life but also durability of errosion-resistant coatings on the mold. It is expected that the siliconized metal mold contributes greatly to the further development of the casting iron by metal mold.

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The behavior and composition of a cathode film formed on a steel cathode during chromium plating were studied with radioactive tracers. A special cell with a rapid washing compartment was used for preventing the cathode film from dissolving in electrolyte after plating. The cathode film was composed of two layers. The outer layer facing to the electrolyte had a loose structure and contained more sulfuric anions than the inner layer, for sulfuric acid probably concentrated in the outer layer. This outer layer is called L-film in this paper. The L-film was easily dissolved in the electrolyte solution. The inner layer (called C-film, compact film) was stable against electrolytes and contained less anions than that of L-film. The C-film had a thickness equivalent to 5mg/m² and the concentration of anions unaffected by the composition of electrolytes. The C-film was not reduced to metallic chromium, but it remained in the cathode film during and after plating. This suggests that chromic acid in the cathode film is not reduced to metallic chromium, that metallic chromium is deposited from chromium complexes reaching the cathode surface through the cathode film, and that the complexes do not play a role on the construction of the cathode film.

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The rise in temperature of the substrates in vacuum evaporation is a significant problem for the metallic coating of less heat-resistant materials. To reduce the temperature rise, evaporation is frequently conducted by use of shielding plates placed between the evaporation source and the substrates. This study has been made to determine the effect of the evaporation conditions on the rise in temperature of the substrates for the system having a shelter. The characteristics of the temperature rise for the shielded system are basically the same as those for the non-shielded system. Shielding has a marked effect on lowering the surface temperature for the substrate materials which otherwise are subjected to the rise in temperature. The temperature rise can be reduced, on average, to almost zero during evaporation. Prevention of the irradiation of the reflected heat radiation to the substrates, enabled by placing shielding plates, would be favorable for the measurements of the properties of evaporated films. It was also found that the temperature rise is influenced by the amount of absorption of reflected radiation as well as the evaporation energy value. The rise in temperature of the substrate materials for a definite thickness of evaporated films can be reduced with increasing deposition rate.

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The polarization behavior of nickel has been studied in the electroless nickel plating baths. The baths consisted of 0.2mol/l of potassium pyrophosphate and various concentrations of nickel chloride and potassium borohydride. The rate of electroless plating of nickel was also estimated by three electrochemical methods; Tafel extrapolation, polarization curves in the absence of either KBH₄ or NiCl₂, and polarization resistance. In the absence of KBH₄ or NiCl₂, both the anodic and cathodic polarization curves obeyed the Tafel relation. In the net electroless plating baths however, the anodic polarization curves exhibited a steep current rise followed by a limiting current, while the cathodic polarization remained unchanged. The results indicate that the anodic oxidation of KBH₄ is affected by the presence of simultaneous cathodic deposition. Consequently, the estimation from the polarization curves in the absence of NiCl₂ gave a higher plating rate than that by weight gain method. On the other hand, the rate estimated from the polarization resistance in the net electroless baths agreed fairly with that of weight gain method under a proper assumption. It is concluded that the rate of the electroless plating of nickel in this bath can be continuously monitored by the polarization resistance method.

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