Platinum anode in the plating solution is insoluble. Decomposition voltage of the plating solution is 1.5volt approximately. The relation between bath voltage and current density is very regular. The higher the current density is, the higher are the bath concentration and temperature.
When the bath solution contain a considerable amount of chloride, too small amount of Na₂HPO₄⋅12H₂O, or the plating time is long at higher bath voltage, the anode is covered with yellow film and the risistance of electricity is increased.

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During the anodizing of aluminium the surface state varies by oxidation and dissolution.
The appearance is not always the same according to the kind of electrolyte; for example, in the case of using sulphuric acid bath, the surface shows an extremly irregular appearance, and in the case of using phosphoric acid bath, it consists of the collection of pits, which are very much like those etched by sodium hydroxide. The observations of the forming-points of nuclei by instantaneous electroplating of such surfaces revealed the followings:
In the case of using sulphuric acid bath, the nuclei are formed starting from the defects on the surface, having nothing to do with the state of oxidized surface, and in the case of using phosphoric acid bath, they are formed mostly around the pits on the surface. The sections across the surface also show that these nuclei have settled mostly on the protrusions from the surface.

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Anodic Oxidation of duralumin type Al-Cu-alloys such as 11S, 17S and 24S is regarded to be generally difficult. It is because of the corrosion that sometimes occurs just after the electrolytic treatment of them due to the effect of their copper content. In this study various experimens on 11S have been couducted by changing the conditions of electrolytic treatment, such as of voltage, current density, components of bath, temperature, and time, respectively. As a result, it has been revealed that anodic oxidation could be carried out without any trouble under proper experimental conditions.

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For the purpose of investigating the brightening mechanism of bright copper cyanide bath, the polarization of cathodic deposit was measured, for which a Haring Cell improved so as to be suitable to cyanide complex was used. The result is as follows:
The polaization of cathodic deposit increases with an increase in copper concentration, with a decrease in free alkali cyanide concentration, with an increase in K⁺ concentration, and with an increase in temperature. It also increases with an addition in brightener when the current density is low, but decreases with an incrase in current density.
Comparing the above result with the range of brightness in the previous report, it is revealed that the factors that decrease the polarization would make the range of brightness broad.
Next, for the purpose of checking up the cause of improvement of brightening by potassium complex and potassium salt, the conductivity of plating bath was measured. As a result, it is recognized that the conductivity increases with the presence of K⁺, which, however, does not seem to be one of the leading factors.

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The conclusion of the previous report concerning the phosphoric acid treatment was as follows:
There remains no phosphoric compound on the surface of aluminium alloy plates, if it is rinsed immediately after the phosphoric acid treatment. However, when the plates are dryed after phosphoric acid treatment, the phosphoric compound adheres strongly on the surface notwithstanding the violent rinsing operation. In this report, the positions of phosphorus deposited on the surface of aluminium alloys are revealed by the autoradiograph of P³². As a result of the experiment, the positions of P³² distribute on the surface according to the structure of the aluminium alloys.
It is not clear that whether the phosphorus deposited on the surface of aluminium alloys is a different compound or the phosphoric acid solution itself remained in small cavities. In any case the phosphorus (P³²) is in the insoluble state, because the testpieces of the autoradigraph are rinsed very thoroughly.
As to Al-Mg alloy, the film of phosphoric compound seemes to grow over thesurface of the alloy. As to Al-Si alloy and Al-Si-Cu alloy, the phosphoric compound seems to deposit in the cavities of eutectic structure. As to Al-Fe series alloys, the phosphoric compound seems to deposit rather on the crystal of FeAl₃ than in the cavity of crystal boundary of FeAl₃. In brief, the deposition of phophoric compound by the phosphoric acid treatment does not cover all over the surface aluminium alloy but partially over it according to the microscopic structure of aluminium alloy.

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