Electrolytic polishing of Aluminium and its alloys in AlCl₃-LiAlH₄-Et₂O solution was studied.
Anodic polarization in the above bath was measured with pure Aluminium plate as an anode and pure Aluminium wire as a reference electrode. The current density-bath voltage relationship similar to the Jacquecurve was obtained in the same bath using Aluminium and its alloys as an anode.
Optimum conditions were established for the preparation of a bright surface of the Aluminium samples.
Aluminium electrodeposits with high lustre was obtained by the electrodeposition of Aluminium followed by the electropolishing in the AlCl₃-LiAlH₄-Et₂O bath.
The condition under which metal specimens can be produced by electropolishing for the examination by electronmicroscopy was fixed.
The electropolishing was applied not only to pure Aluminium but also to Al-Cu, Al-Fe, Al-Cr, Al-Mn, Al-Si, Al-Ti, Al-Zr and Al-Mg alloys.

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Chemical plating cost will be reduced, if the life of bath becomes so long that the bath can be used repeatedly after purification. The authors have been investigating the life and reproduction of chemical plating bath in commercial point of view. In this paper, the relations between the volume of plating solution and plated area, as well as the particular concerning the reproduction of the plating solution, are reported as follows:
1) It is necessary for long life of plating bath that the volume of plating solution is increased in comparison with plated area.
2) It is, however, desirable that the ratio of volume of solution and plating area (V/A) is less than ten.
3) In reproducing the plating solution detrimental phosphorous ion, should be removed, as well as nickel and hypophosphorous ion should be supplied, and value of pH controlled.
4) It is possible to make the life of plating bath long and to prevent the precipitation of nickel salts by the addition of organic acid such as propionic acid or lactic acid.

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Proper disposition of impurities, etc., in plating bath is prerequisite, for obtaining the best plating result. The authors have been investigating, from the commercial point of view, the effect of impurities in chemical plating bath and galvanic action at the starting period of plating for the purpose of getting the good adhesion of the deposit, the result of which is reported as follows:
1) As in the case of electroplating impurrities in chemical plating bath such as ferrous, cupric and zinc ion have bad effect upon the appearance of plating and plating bath.
2) As for the ferrous ion, even its very small amount existing in the bath not only deteriorates the surface of the deposit, but makes the bath turbid.
3) Presence of cuprie ion in plating bath results in the appearance of black streak and brown color on the surface of the deposit.
4) The presence of zinc iron in plating bath makes the plating efficiency very low.
5) Galvanic action generates by the contact of iron with aluminum improves the adhesion of the deposit even on copper and copper alloys.

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Formation of bright deposits and cathode polarization in cyanide silver plating bath were studied.
Current density-cathode potential curves were determined for the deposition of silver from a solution of KAg(CN)₂ 0.2N, KCN 0.6N, K₂CO₃ 20g/l, in the presence of various addition agents.
The results obtained are as follows:
1) Addition of sulfur compounds, such as Na₂S₂O₃, C₂H₅OCS₂K, CS(NH₂₎₂, C₃H₅NHCSNH₂, C₃H₅NCS, mercaptbenzothiazole and mercaptbenzoimidazole decreases the cathode polarization and the surface of deposit is usually fine and bright.
2) Butyne-diol (1, 4), propargylalcohol, coumarin and heliotropine are found to be ineffective in the formation of bright deposit and generally result in the higher polarization.
3) Commercial brighteners, such as K-Sb-tartrate, Sb₂O₃-glycerin, acrolein-urea-hexamethylenetetramine and acrolein-C₂H₅OCS₂K decrease the cathode polarization.
4) That the cathode potential becomes less negative with the addition of sulfur compounds seems to be due to the activation of the electrode by adsorption of colloidal substances derived from the addition agents or their reaction products.

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As plating time passes, in the acid electroless nickel plating solution containing sodium hypophosphite, phosphite ions are produced and accumulated. When the amount of the ion is increased over a limiting value, nickel phosphite cristalline is formed and suspended in the solution, which cannot be used any more.
The limiting value of accumulation of the phosphite ions under various conditions was investigated from the solubility of nickel phosphite and the amount of sodium citrate added to prolong the life of the solution was also estimated, and the composition of the electroless nickel plating at pH 5.0 was determined. It was found that the life of the electroless plating solution could be estimated through the composition and the pH of the solution.

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The effects of chromium layer on the corrosion protection of decorative chromium plated steel panels were investigated. In this series of corrosion study the Sargent type chromium plating baths were used with varied chromic acid concentrations.
Accelerrated corrosion test of the nickel-chromium plated steel panels showed that the effect of increasing chromium thickness is greatly changed with the type of underlying nickel layer. Thus the plated panel with underlayer of Ni-Cr alloy of relatively rich ductility but high internal tensile stress loses corrosion resistance with increasing chromium thickness. This is clearly due to the crazing of nickel layer along the cracks of outer chromium layer, although the tendancy decreases with an increase of chromic acid concentration in the chromium plating bath.
On the contrary, the plated panels with the underlayer of levelling bright nickel showed little deterioration with chromium thickness increase, even in the low concentrated chromium bath.
Furthermore in this case, increase of chromium thickness by using high concentrated chromium plating bath increases corrosion resistance.
Then, the corrosion resistance test of copper-nickel-chromium layer of the same thickness as the above nickel chromium plating was carried out, and is found that in the case of Ni-Cr alloy as intermediate layer, the presence of copper layer depresses deteriorating effect caused by the increase of chromium thickness.

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Complex salt of copper and zinc cyanide is decomposed into CuO and ZnO, by H₂O₂, and then dissolved in HNO₃.
Zinc can be titraled by EDTA in the presence of copper which is masked by adding a slight exess of thiosulfate at pH 5-6, using methanol and the PAN (α-pyridyl-β azonaphtol) indicator.
Then copper is analyzed with EDTA, after breaking down the copper masked by thiosulfate, using hydrogen peroxide as fellows:
2Na₂S₂O₃+H₂O₂→Na₂S₄O₆+2NaOH
The end point of above reaction is told by PAN indicator.

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Current inhibiting action in anodizing have extensively been examined with 10vol.% sulfuric acid and direct current, 99.999%Al, 99.99%Al, 99.85%Al, 1S, 17S, 52S, 63S, hydronalium, silumin; aluminum mother alloys such as Al-Cr, Al-Si, Al-Ni, Al-Mn, Al-Cu; copper, steel, lead, stainless steel (18Cr, 18-8) and titanium being used as specimens.
With the pure aluminum materials, current inhibiting action was stronger in the order of 1S, 99.85, 99.99 and 99.999. Supposedly the impurities in aluminum play the part of inhibiting the anodizing reaction. V-D_A curves obtained from those materials could be classified into 3 types, namely, swift upward, steadily increasing and fluctuated types as shown in Fig. 7-9. Each curve well shows how the action occurs.
Titanium showed the strongest inhibiting action, and V-T relations of this material were studied under constant D_A as shown in Fig. 6.
Next, partial distribution of current was examined about most specimens mentioned above; that of 99.99%Al or titanium being taken as standard anode. The connection of electrical circuit of this experiment is shown in Fig. 1.
Results obtained will help select the practical method of anodizing the products composed of the different materials, and suitable materials for racks and tools of commercial use.

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