Studies were made on the blisters which appear on the plated surface of zinc alloy die castings after several months more since the plating. The processes for accelerating the appearance of these blisters were also discussed. The following results were obtained
(1) Each blister had a circular gap of 30-40μ in dia. at its centre, from which cracks radiated.
(2) Growth of blisters was due to the corrosion of the substratum of zinc alloy.
(3) For accelerating the appearance of blisters, it was found to be most effective to immerse the castings in the solution of about 3% of NH₄Cl in boiling.
(4) The blisters appeared in the above test were considered to be the same in nature as that in practice. Accordingly, the above test would be most available for detecting the surface defects for blistering source.

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Grease-base Compounds are generally used for giving gloss to table and kitchen wares made of stainless steel. However, the effects of these compounds for gloss-buffing have not yet been scientifically studied, and the practical buffing operations in workshops are mainly relied upon the skill of operators.
The object of the authors' study is to manufacture excellent gloss-buffing compounds.
The authors analyzed the gloss-buffing compounds employed in Tsubame, Niigata Pref. and studied the relation between the elements of the compounds and the effects of gloss-buffing.
As the results, it was found that all of gloss-buffing compounds employed in Tsubame are composed of the finest abrasive grains in a binder of oils and fats having deep effects on glossing.

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The phase changes in electrolytic Co-P deposits during heat treatment are reported in this paper.
The experimental methods in thermal, magnetic, and X-ray analyses were the same as those in the previous reports. The results obtained were as follows:
(1) The hardness at each temperature during heating or cooling was measured with Micro Vickers Hardness Tester for high temperature. As the results, the maximum hardness was confirmed to be at about 380°C.
(2) The exothermic changes of these deposits showed similar behavior to that of electroless Ni-P deposits.
Judging from the X-ray diffraction pattern for electrolytic Co-P deposits, it was possible to confirm that cobalt phosphide had been formed at the temperature of exothermic change.
(3) Susceptibility of electrolytic Co-P deposits at room temperature was lower, as compared with that of electrolytic pure Co deposits.
The curve for magnetic analysis in the heated state showed that the susceptibility rapidly increased at 310°C.

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In the previous paper, the author reported the relationship between additives and their brightening effects on copper cyanide plating baths. The results showed that the additives yielding bright copper deposits included the compounds containing sulfur such as thiosulfate, thiocyanide, xanthogenate, etc. and the inorganic compounds containing Pb, Te, etc.
In this paper, for the purpose of investigating the brightening mechanism of these additives, the effects of the above additives, bath compositions, and operating conditions on the cathode polarization were determined.
The results were summarized as follows:
1) The cathode polarization of copper deposition decreased with the increase of metallic copper concentration, decrease of tree cyanide concentration, elevation of bath temperature, and with agitation. However, little effects were given by employing PR (Periodic Reverse) current on the cathode polarization. Then, there would be very little cathode polarization in reverse current.
2) In the baths containing lead compound, the cathode polarization increased at low current density. Then, the deposition potential of copper would be elevated owing to the deposition of lead. On the other hand, in the baths containing a large amount of tellurium, the cathode polarization slightly decreased. Hence, the effects of these additives on brightness would be due to the deposition of these elements together with copper.
3) In the baths containing the above sulfur compounds, the cathode polarization remarkably decreased and more and more decreased with air agitation and employing of PR current at high operating temperature. Hence, the beneficial brightening effects of sulfur compounds would be due to the grain refining of crystals by the deposition of a small amount of sulfur together with copper.
4) The addition of organic compounds had little effects on the cathode polarization. However, the addition of a large amount of nonion surface active agents exerted a slight decrease in cathode polarization and somewhat improved the brightness of copper deposits.

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