Zinc immersion treatment on the surface of aluminium alloys was investigated, for the purpose of fixing the conditions for commercial operation as follows:
(a) Alkaline solution
NaOH (Sodium hydroxide) 120-525g/l ZnO(Zinc oxide) 20-100g/l
Temperature 5-25°C Suitable for Al-Siand Al-Cu-Si
(b) Acid solution
ZnSO₄ (Zinc sulfate) 500-750g/l HF (48% vol) (Hydrofluovic) 0.5-1.5cc/l
Temperature 10-25°C Suitable for Al-Mg

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As reported previonsly, internal stress in flame sprayed procelain enamel coating is larger than that in ordinary baked coating, and by this reason, the flame sprayed porcelain enamel coating is more sensitive for mechanical and thermal schock.
In order to avoid this defect, the authors tried to improve the method of spraying and got the following results.
1. By spraying at high temperature (650-750°C), moderately thick intermediate layer is formed between base and coating and the coating is adherent and stands schock as ordinary baked coating.
2. By the addition of pyrophyllite in the flit, and by shortening the time of melting, good adherent coating is obtained. This is due to the reduction of internal stress in the coating.
3. By the application of very brittle flit as under coating, shock-resistant adherent coating is obtained. This seems to be due to cusioning action of crack in the under coating.
4. It is possible to spray porcelain enamel on the old coating. But, in this case, operator should be done with great carefulness in order to avoid crazing, chipping and fishscaling.

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Phosphating practice has been much improved in the bath composition. Heretofore some nitrates have been used as accelerator by adding to the conventional phosphating bath, however, there have appeared the chlorate-acceleraters in the recent literatures and patents. The result of investigation on this new method of chlorate-accelerated phosphating bath is reported in the present paper.
Some of the behaviours of the bath in solution and the properties of the phosphate coatings were observed. In summary, the followings are proposed:
1) The suitable compositions of the bath are
Zinc powder 5-8g/l Acetic acid 3-8g/l
Phosphoric acid 30-45g/l Potassium chlorate 1-3g/l
Caustic soda 3-4g/l
2) This solution exhibits a milky turbid colour followed by development of colloidal suspension, which hardly appears in the solution of composition range under 0.3% KClO₃.
3) The deposition of fine grained phosphate-coating on the steel surface dipped in the bath's, completed in 15min. at 50-60°C.
4) The thickness of coating is about 17μ and the spontaneous electrode potential in 3% NaCl solution of the coating formed by this method, is nobler than that of the coating formed by the conventional method. Therefore, the coating of the former seems to be more anticorrosive than the later.

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(1) Even if (NH₄)₂HPO₄ is added more than 30g the current density and depositing quantity do not increase.
(2) If Na₂HPO₄·12H₂O is added more than 300g the current density and depositing quantity decrease.
(3) If much (NH₄)₂HPO₄ is added brightness of plating surface immediately fade away.
(4) Influence of Na₂HPO₄·12H₂O on brightness of plating surface is very small.
(5) As plating time goes on color of plating surface changes to light brown, then to brown and then to black.
(6) The platinum amount of electrodeposition increases with a decrease in pH value in the plating solutions, More than 12.3pH, plate hardly. When the pH value becomes over 12.3 platinum is not deposited.
(7) When the plating solution of lower pH values is used, the brightness of plating surface soon fades away.
(8) That the color of plating surface changes to black is accounted for the electrodeposition of platinum black.

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