Relation between porosity and thickness of sprayed Aluminum coating on steel was studied by means of “ferroxyl test, ” applying an external e.m.f. as follows:
Specimens were connected to the positive pole of D. C. source, and placed under the filter paper impregnated with the solution, on top of which the negative pole of carbon plate was placed.
Composition of the solution:-
Sodium chloride 60grams
Potassium ferricyanide 10grams
Potassium ferrocyanide 10grams
Water to make 1 liter
Current density used was 0.2A/dm², and test time was 5min.
As a result, an empirical formula, yx^2.3=0.12, was obtained, where y is the thickness of sprayed Al coating, x the number of open holes of the coating, and the relation between x and y is given as the above formula.

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The present study was to investigate the behavior characteristics of the cathode polarization in the plating baths consisting either of CuCN-NaCN-Na₂CO₃ or of CuCN-KCN-K₂CO₃.
When the solution was kept unstirred, the cathode current densities of the hydrogen evolution were found to be greater in the solution of potassium salt than that of sodium salt. Consequently, cathode polarization was less in the potassium salt solution than the corresponding sodium salt at the low current density range.
The cathode polarization of copper deposition decreased considerably when the solution was stirred, and the current densities of the hydrogen evolution increased. In the potassium salt solution, more pronounced effect was observed than in the sodium salt solution.
The marked influence of the stirring in reducing cathode polarization suggests that the polarization is solely controlled by diffusion. In all cases, however, the change of the mole ratio, [CN]/[Cu], of the constituents in the vicinity of the cathode must be taken into account.
The fact that the effect of stirring in reducing the polarization was more pronounced in the bath of potassium salts than that of sodium salts led us to the following conclusion:
There seem to exist the characteristic differences in the mechanism of the electrode processes during the deposition of copper on the cathode depending on the constiluent of copper cyanide solution of sodium or potassium salt.

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Simple method for the determination of zinc oxide in the sprayed zinc coating is not yet provided, though it is quite important in the inspection of quality of coating. The authors' effort is, therefore, mainly focussed to obtain methods for practical use.
First, we tried to estimate the oxide content from the volume of hydrogen gas evolved when the coating was dipped in acid solution. The volume changed sensibly as was expected, with the change of oxide content. After many tests, it was found that, this method could be used for practice if the temperature of the gas was regularly controlled by proper apparatus.
Second, the coating was tried to dissolve in the potassium iodide solution containing iodine. By this treatment, not only the metal, but also a small amount of oxide are dissolved, which makes the determination not simple. Thus, it seems that, for practice, the first method is better than the second with respect to operation, accuracy and cost of analysis.

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Silver deposits obtained from cyanide bath with various addition agents were studied by electron diffraction analysis and also by photomicroscopy to elucidate the characteristics of the crystal structure of bright deposit formation.
Addition of inorganic sulfur compounds such as, Na₂S₂O₃⋅5H₂O and KSCN resulted in a semi-bright deposit, however, no preferred orientation of the crystals was observed in the deposit.
Organic sulfur compounds, such as thiourea, allyl thiourea, phenyl thiourea, allyl isothiocyanate, mercapto-benzimidazole, mercapto-benzothiazole, etc., gave rise to bright deposits with a moderate or strong preferred orientation of crystal.
Organic unsaturated compounds, such as coumarin, heliotropine, etc., used as effective brightener in Zn or Cd cyanide bath, produced a rough and matte deposit without preferred orientation of crystal.
It was found that there was no direct relationship between the degree or type of preferred orientation and the brightness of the surface.
Addition agents in the Ag cyanide bath seemed to make the deposit bright and smooth due to the fine grain formation rather than the preferred orientation of crystal.

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