CHARACTERIZATION OF ZINC-COBALT ELECTRODEPOSITS

The structure and morphology of electrodeposits depend on many factors including temperature, current density, time of deposition and compos ition of the bath. The properties of an electrodeposit depend on its m icro structure. For example corrosion and wear resistance, hardness, i nternal stress, strength, brightness, electrical conductivity, magneti c properties and leveling are all affected by structure. The relations hips between electroplating parameters such as current density, temper ature, bath agitation and electrolyte composition have been investigat ed for the zinc-cobalt system. It was found that electrolyte compositi on and temperature affect both deposit composition and morphology. The cathodic current efficiency decreased with current density and hardne ss was raised with increasing cobalt content in the deposit. Three pow erful techniques were used to access the microstructure of zinc-cobalt deposits: scanning electron microscopy, transmission electron microsc opy and X-ray diffraction. The results show that the alloy is constitu ted of a single phase of a solid solution of cobalt dissolved in zinc within an hexagonal crystal system. The deposit is porous and changes from dendritic to nodular with increasing cobalt content.