The wear-resistance test of chromized steel has been carried out to the nitrided drum in a dry wear-state, and its resistivity is compared with chromium electroplated steel. It is determined that the Chromized steel is more excellent than electroplated steel in the long length of rubbing, but in the short length, the latter is excellent.

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The method of aluminium coating on iron by hot dipping process was studied. The effect of dipping time, tempereture and composition of bath on the thickness of diffused interfacial layer was dicided. To diminish the brittle interfacial layer, aluminium alloy containing silicon or copper is effective. But silicon is preferable than cupper to protect iron from corrosion. The aluminium coated iron can also be applied for anode of vacume tube instead of nickel.

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The facility of passivation for zinc anode is dependent upon the measures of immersing area of the electrodes.
The passivation voltage and the electricity at the very moment of passivation became increased in accordiance with the enlargings of the surface area of the anode in a dilute solution of zinc sulphric acid. The more, in this experiment, the surface areas of the cathode became large, the less measured was the passivation voltage. On the contrary, the electricity, after passivation, became, on one hand, slightly increased in the same situation, when, on the other hand, the surface area of the anode was smaller compareing with that of the cathode, the electricity became slightly decreased.
The reason for these difficulties of passivation in accordiance with the enlargingness of the surface areas of the anode in an active condition in the aqueous solution of electrolytes of the same quantity is accounted for by the coincident fact of this experiment with the theory of electric decomposion, that is, a negative compound in the solution has its hard tendency, in an action of passvation, to combine with on the surface of the anode in proportional to the enlargingness of the anode. This leads us to conclude the evident fact that the electritic decomposition in the aqueous solution of electrolytes takes a leading part in the occurance of the passivating phenomenoa.

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Supersonics (frequency 620 K. C.) have been radiated upon the anodes of Al in oxalic acid solution, that of Cu in HCl and CuSO₄ and that of Fe in H₂SO₄ solution.
By the radiation of supersonics passivation has been promoted in the case of Al, whereas in the case of Copper and iron, it has been retarded.
Peculiar phenomena occured in the latter case, i. e., higher bath voltage has been required in dissolving copper and iron from the anode at very low current densities when exposed to the radiation of suppersonics.

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Although iron shows the most conspicuous example of metal liable to become passivized, inasmuch as it being bad metal, it is generally corroded. However, it becomes corrosion-proof owing to a stable film produced when it is passivized. So, it is acommon practice to apply such a method of alkali coloring, parkerizing or bonderizing. But, in this experiment, a research was made into a corrosion-proof nature and rust-preventive power due to treatment and work, after a coloring measurement has been made by means of potassium ferro cyanide on divalent ferro iron which is dissolved in dipping solution, in an aim of making a deriveration on the treatment and work so as to maintain the grinding brilliance and corrosion-proof nature.

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