The authors investigated the thickness of the aluminum film that adhered to flat steel plates by hot-dip coating under stationary conditions, and compared the theoretical values with the measured ones. The quantification of the thickness of the aluminum film was done under experimental conditions, as follows:
temperature of the molten aluminum: 750°C, atmospheric temperature: 590, 680°C, withdrawal speed: 0.5, 1.0, 1.5, 3.6, 16, 30cm/s.
The results showed that the film thickness on flat steel plates becomes thicker by increasing the withdrawal speed and lowering the atmospheric temperature. The film thickness can be expressed by the following exponential equation when the atmospheric temperature and temperature of the molten aluminum are constant.
h_ov=C·v_wⁿ
where h_ov: thickness of the aluminum film, C: constant value settled by the atmospheric temperature, v_w: withdrawal speed, n:n≅2/7, provided temperature of the molten aluminum is 750°C and the atmospheric temperature is 590-680°C.

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Chromium coatings electrodeposited from Sargent bath (50°C) at a current density of 30A/dm² by using rippled direct current of various frequencies were investigated by hydrogen gas analysis method, microscope, and X-ray stress analyser. Heating the chromium coatings, consisting of both hcp and bcc crystals, caused generation of hydrogen gas and disappearance of the X-ray diffraction line due to the hcp crystals. A close correlation was observed between the quantity of hydrogen gas and the content ratio of hcp crystals. In the transition state from mixed crystals to bcc crystals only, the cracks seemed to be caused by a shrinkage force, which overcomes the bonding force of the chromium. And the number of cracks on the surface observed was also proportional to the content ratio of hcp crystals. The cracked coatings became almost free from stress. However, the surface and the stress of as-electrodeposited chromium consisting of only bcc crystals did not show any change after heating. Crack-free coatings of relatively high hardness were obtained in the range of 1.4kHz to 5.0kHz ripple frequency of the direct current.

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The author studied the application of impulse current produced by instantaneous discharge of energy, which had been charged in a capacitor, to a tungsten filament in a vacuum. It was found by the author that the filament was explosively dispersed under specified conditions of electric circuit and discharge energy. The filament was dispersed into gaseous state by high discharge energy; or by concentrated energy resulting from reduced circuit inductance. For instance, the dispersion into gaseous state was obtained by the application of a current higher than 1 kamp through a filament of 0.2mm in dia. and 5mm in length; but the filament was dispersed into spheroidal balls under a current of lower than 1 kamp. A thin crystalline tungsten film was formed on a substrate placed near the filament, and the average thickness of the film violently decreased with an increase of energy. The film formed from the gaseous state was larger in thickness than that formed from the dispersed spheroidal state. The number of grains in these thin films depended on the discharge energy and circuit inductance. More grains were contained in the film by the discharge under lower energy or higher inductance; and grains were less in the film formed from the gaseous state that formed from the dispersed spheroidal state. In particular, very few grains were contained in the film formed from the gaseous state by the discharge of low circuit inductance.

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Anodizing characteristics of Al in high temperature solutions of tartaric, malic and malonic acids were investigated. Aluminum sheets of 99.99% were anodized in 1 and 3mol/l solutions of these acids at 40-80°C and at current densities of 4.67-18.7A/dm². Uniform and integral-colored films without cracks were formed on Al at relatively high temperatures and low current densities. Bath voltage during anodizing in the malonic acid bath was below 100V, whereas in the tartaric or malic acid bath it was above 150V. In the malonic acid bath, hard films of Hv 450-550 were obtained only below 60°C, whereas in the tartaric and malic acid baths hard films of Hv 550-700 were produced even at temperatures between 60 and 80°C. Hardness values generally increased with elevating temperatures, lowering concentrations and increasing current densities, viz, with increasing bath voltage. The coating ratio increased as temperature was lower and current density higher. In the tartaric acid bath, the recovery of current was observed after a sudden drop of anodizing voltage. During the recovery, the size of the cell became smaller and the number of the cell increased. Therefore, anodic oxidation of Al in these baths was found to be essentially the same as that in sulfuric or oxalic acid bath.

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A modified type of conventional multiple countercurrent rinsing, defined by the authors as a batch type, has been proposed. In this type of rinsing, water is not supplied continuously by running water, but periodically by batch operation. When the salt concentration in the 1st rinse tank of multiple rinses reaches a certain value, the whole water in this tank is drained. Then the rinse water in the 2nd rinse tank is pumped out into the 1st rinse tank, followed by the same pumping out operations. After the whole water in the last rinse tank has been pumped out, fresh water is supplied into this emptied tank by batch operation. The following cycles of rinsing are thus repeated without running water supply. Mathematical equations for estimating the maximum salt concentration in each rinse tank at the end of each rinsing cycle have been derived. Although these mathematical calculations were complicated, theoretical values of concentrations could be obtained as output data of electronic computer which was programmed by these equations. From these data, it was found that this modified type of multiple rinsing has advantages that rinsing can be carried out with less water supply and with higher recycling efficiency of drag-out salt in the lst rinse as compared with the conventional type of rinsing.

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Effects of metallic contaminants, such as Na, Mg, Zn, Cd, Ni, Cu, Fe, Cr, Hg, In, and Tl in low concentration chromium plating bath (CrO₃ 50g/l, H₂SO₄ 0.5g/l and Na₂SiF₆ 0.5g/l) were investigated. 1) An addition of metal oxides or hydroxides of 0.15g. eq/l resulted in the burnt deposits at high current densities and by the further addition of metals of 0.25g. eq/l and 0.35g. eq/l no chromium deposit was obtained at current densities of above 50A/dm² and 15A/dm², respectively. When the amount of metals was increased to 0.50g. eq/l complete loss of chromium plating was observed independent of the metal species studied. 2) Metals of I B, II B and III B groups in the periodic table were found to improve the covering power of chromium plating and it is noteworthy that these metals have the high hydrogen overpotentials. 3) When an addition of NiSO₄⋅7H₂O or CoSO₄⋅7H₂O was above 0.2g.eq/l, Ni-Cr or Co-Cr alloy was deposited in a reproducible manner.

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