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The covering powers of chromium platings from both of the plating baths of low and high concentrations were studied.The following results were obtained:(1) The covering power by the Hull Cell Test was much higher in the bath of low concentration than in that of high concentration.(2) On the contrary, the covering power by the parallel or bend cathode process was lower in the bath of low concentration than in that of high concentration.(3) The above two contradictory phenomena were due to the fact that the current was likely to be concentrated along the edges of the specimen so that the current density in the center was lowered; and the lowering degree of the current density was greater in the bath of low concentration than in that of high concentration.

The throwing power of various nickel plating baths were measured by the Hull cell method, in which throwing powers were expressed in terms of thickness of deposits measured at various points across the cathode, and of primary current distributions derived from the conventional Hull cell current density formula.The effects of current density and of bath compositions on the throwing power of nickel were studied. Among the nickel plating baths, studied, the highest throwing powers were given by dull nickel, all-chloride, NaCl, and high-sulfate nickel solutions. However, Watts, sulfamate, high-sulfamate, and KCl nickel plating baths gave moderate throwing powers, and fluoborate and citrate baths gave low throwing powers.The effects of sulfates on the throwing power and electrolytic conductivity were studied in the Watts bath. It was found that the throwing power and conductivity were improved by raising the concentration of sulfate such as K2SO4, Na2SO4, (NH4)2SO4 and MgSO4.

Electrodeposition of lead is performed to deposit an acid-resistant coating for containers directly onto steel or cast iron. It is commonly done in fluoborate, fluosilicate and sulfamate baths.In this study, the alkaline lead gluconate was used as a new electrolyte in lead depositing bath.The following results were obtained.(1) The most suitable composition of electrolyte for the best results were as follows:2PbCo3·Pb(OH)2 200g/l, (C6H11O7)Na 100g/l, NaOH 100g/l, glue 0.2g/l, red-oil 1 drop/l(2) The cathode current efficiency was 99% up under current density of 5A/dm2 and at bath temperature of 70°C.(3) It was shown by Hull cell method that alkaline lead gluconate bath gave higher throwing power, as compared with fluoborate or fluosilicate bath; the power was more increased when its temperature rise to 70°C or a small amount of additives such as glue and red-oil was added.

Usually the covering power value of the chromium plating bath deviates markedly when measured by Hull cell test. Experiments were carried out in order to investigate the cause of the deviation, and to find the better pre-treating method of the cathode which gives better reproducibility in the test result. Results are as follows:(1) Cyanide bath dipping and chemical polishing of the cathode (copper), especially the latter, increase covering power value remarkably.(2) In chemical polishing the brighter the surface of cathode, the less was the deviation.(3) The least deviation was obtained by using the cathode uniformly electro-plated about 10 microns thick.

By measureing the current efficiencies and by the Hull cell test, the unfavorable effect and the permissible amount of anionic impurities such as Cl-, NO3-, and PO43- were studied on the Sargent bath (CrO3 250 and H2SO4 2.5g/l) and the bath contining sodium fluorosilicate (CrO3 250, H2SO4 1.5, and Na2SiF6 5.0g/l).Each impurity decreases the current efficiency and brightness range. The permissible amount of each impurity is as follows:Cl- is 1g/l (as NaCl) for the both baths, NO3- 1g/l (as NaNO3) for the Sargent bath and 2g/l for the sodium fluorosilicate bath, and PO43- 4g/l (as Na2HPO4⋅12H2O) for the both baths.At the range of so low current density as not to deposit Cr, the base metal of copper, nickel, or iron dissolves into the both baths containing Cl-.