Electrodeposition and corrosion performance of Ni-Co alloys with different cobalt contents

The deposition mechanism of Ni-Co alloys with different cobalt compositions plays an important role in the preparation and application of Ni-Co alloys by electrodeposition. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were used to study the effect of the Co content on the electrodeposition mechanism of the plating. The surface morphology and crystal structure of the plated layers were studied by scanning electron microscopy and X-ray diffraction. The corrosion performance of nickel-cobalt alloys with different Co contents was analyzed by anodic polarization curves and electrochemical impedance spectroscopy. The results showed that during the early stage of electrocrystallization, increasing the CoSO4 content in the plating solution decreased the charge transfer resistance during nucleation and decreased the activation energy of nucleation/growth. Nucleation occurred via a three-dimensional transient nucleation mechanism, which was controlled by both diffusion and electrochemical factors. Compared with pure nickel, the Ni-Co alloy had a more pronounced (1 1 1) orientation and superior corrosion resistance. Plating with 10 wt% Co provided the best corrosion resistance.