The effects of Cl ion on deposition mechanism and film properties in electrophoretic coating bath of water soluble alkyd primer were studied on steel and aluminum alloys, and the following conclusions were drawn.
(1) In aluminum alloys, the amount of deposition at first remarkably increased with the increase in addition of Cl ion and attained to maximum, and then, decreased. The above phenomena can be explained by the following reason: the increase in deposition amount in the first range was attributed to the prevention of passivity of anode during electrophoresis and the decrease in that amount in the next range was attributed to the increase in film resistance due to the dissolution of anode caused by the addition of Cl ion.
(2) In steel, there is no range of increase in deposition amount due to the addition of Cl ion, because of no passivity of anode. The amount of deposition gradually increased from the outset. The above phenomenon may be attributed to the increase in film resistance due to the dissolution of anode caused by the addition of Cl ion.
(3) In aluminum alloys, the oxidized film on anode formed during electrodeposition had considerable corrosion resistance.
(4) The properties of coated film, both chemical and physical, were not affected by the addition of Cl ion in the range of 0-70ppm.

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In the previous papers, the author discussed the effects of plating conditions and additives on bright and leveling action and cathode polarization in copper cyanide bath. It was found that these conditions had very significant effects in deposits. Judging from the above fact, the plating conditions and additives may have some effects on crystalline structure of copper deposits.
In this paper, there are reported the results of observation of crystalline structures by means of X-ray diffraction and observation of surface appearance by electron microscope.
The results were summarized as follows.
1) The crystal form of copper obtained from cyanide plating bath was quite the same as that of copper obtained by other processes, or it was face centred cubic lattice.
2) The crystalline structures of the deposits from non-additive baths had no orientation, but the grain size of crystallites was relatively larger.
3) Lead deposited from the baths, into which lead salts had been added. It formed crystal nuclei, from which copper crystallized radially in all directions. Accordingly, the surfaces were rough and the crystals had no orientation.
4) The copper deposits from the baths containing sulfur compounds, having remarkable effects in brightness, such as thiocyanide, thiosulfate, etc. exhibited very strong orientation on [111] plane and the crystallites were very fine.
5) The copper deposits from the baths containing organic compounds such as surface active agents exhibited weak orientation on [200] plane.

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The object of this study was to clarify the formation mechanism of so-called chromate coatings. This paper relates to the chromate treatment of zinc in dilute Cr (VI) solutions acidified with sulfuric acid. Zinc dust was used, instead of panels, in order to make a large area of surface react at once. Features of the reactions were studied by determining the change of solution composition with the lapse of time.
A significant experimental fact was found; in the chromate solution, of which initial pH was higher than 2.5, a large amount of Cr (VI) was expelled from the solution at the first moment of reaction with superficially oxidized zinc dust, and then, Cr (VI) in the solution increased with the proceeding of reaction. This means that zinc-chromate precipitates on zinc owing to the combination of dissolved zinc oxide with chromate.
It was concluded from the results that all of deposits precipitated at pH near the metal surface was contained in the coating.
A study on the species existing in Cr (III)-sulfate solution was carried out by paper-electrophoresis, which revealed Cr (III)-complexes produced in the chromate solution. The fact that the addition of chromium alum improved the reduction rate of chromate was explained as follows: it was due to the supply of hydrogen ions necessary for the reduction originating from the protolysis of Cr (III) aquo-ions.

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