Abstract
The conditions for obtaining brass platings from non-cyanide bath of the composition mentioned below were studied with respect to polarization curve, analysis of deposited metal, measurement of current efficiency, visual test of deposits, etc. The bath was composed of 60-100g/l of NaOH, 5-20 ml/g of glycollic acid, and ZnO and CuSO4. 5H2O (concentration of total metal ions was less than 4g/l). Summary of test proceduse was as follows. When the polarization was beyond the threshold current density of each metal (about 5mA/cm2), a yellowish brass deposit of normal composition was obtained. However, when the current density was lower than that, only Cu was deposited. The current density was in the range of 80-30% in practice. The efficiency was promoted when the concentration of total metal ions was higher and the current density was lower. The zinc content of deposit was about 5% larger than that of bath composition. The addition of 0.5g/l of glatine gave better appearance of the deposit. When the deposited alloy was settled in the bath for a long period, its color was periodically changed as golden→magenta→blue→green. In conclusion, non-cyanide brass platings were obtained as above under almost the same conditions as in cyanide baths, except for that both of metal concentration and current density are not very high.
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