Abstract
The stability of electrolyte containing cadmium-ethylenediamine (en) chelate in various pH ranges has been investigated to determine the optimum condition for electrodeposition of cadmium. Cathodic polarization measurement was made in the above bath, and the cadmium deposits obtained under various conditions were examined by X-ray diffraction. The results obtained were as follows: 1) Cadmium (II) ions seemed to react with en to form a stable complex, and bright and smooth cadmium deposits on copper plates were obtained over the range of pH 9-12. 2) Complex ions were greatly affected by anion. Cadmium was not deposited from acidic baths containing a small amount of chloride ions and various precipitates such as Cd(en)mCl2(m=1-3), but was deposited from neutral and weak acidic baths. Cadmium-en complex was not formed, when pH-value was in acidic or strong alkaline ranges. In this case, en seemed to act merely as an addition agent upon electrolysis. 3) By the addition of gelatine in to the cadmium-en bath, adherent cadmium deposits having a fine grain (270-290Å) structure were obtained. It was shown by X-ray diffraction analysis that the orientation of the cadmium deposits was strong in (101), but weak in (102) and (103). 4) The optimum composition and operation condition of the bath were found to be Cd (CH3COO)2⋅2H2O: 0.3-0.5mol/l, en: 1.2-2.0mol/l, gelatine: 0.5-1.0g/l, pH: 9-11, temperature: 20-50°C, current density: 1.0-2.5A/dm2; current efficiency was above 90%.
