In this study, the corrosion properties of Zn-Co alloys prepared by the electrodeposition method from a sulfate bath under potentiostatic conditions on steel and aluminum substrates have been investigated. The deposit morphology and elemental composition were examined by scanning electron microscopy (SEM)/EDX. The preferred crystallographic orientations of the deposits have been determined by the x-ray diffraction (XRD) technique. The effects of bath composition on the phase structure, morphology and corrosion behaviors have been studied. It has been observed that the cobalt content strongly affects the structure and corrosion stability of Zn-Co alloys. It was found that amorphous alloys were obtained with high Co contents, while crystalline alloys were formed with high Zn contents.