Electrodeposition of As-Sb alloys

As-Sb alloys containing 30-95 at.% Sb were deposited onto nickel cathodes from citric acid aqueous solutions. The composition of the electrodeposits, determined by scanning electron microscopy--energy-dispersive X-ray analysis approached that of the solution at E ? -0.7 V with respect to a saturated calomel electrode; at less negative potentials the antimony-to-arsenic ratio was higher in the alloy than in solution. The current efficiency approached 100% under the most favourable conditions and was higher at higher temperatures. As codeposition made the antimony deposition kinetics markedly more complicated: a negative slope region was visible in the steady state I - E curves and, correspondingly, the a.c. impedance diagrams showed negative polarization resistance. These phenomena appear to arise because the arsenic-covered areas are less active than the antimony-covered areas.