Investigation of Corrosion Behavior Nanocrystalline Nickel-Cobalt Coating by Electrodeposition

In the present study, nanocrystalline Nickel-Cobalt coating was electrodeposited by pulse current from a Watts bath. Electrodeposition was carried out in the current densities of, 4, 6 A/dm at different frequencies and on-time periods in the baths containing of 0.5,, g/l saccharin. Morphology, analysis and crystallography of the coating were studied by means of SEM, EDS and XRD methods, respectively. The grain size of the coating was also calculated from XRD patterns using Scherrer equation. The results of polarization tests carried out in. 5% NaCl solution indicated that by increasing the cobalt content in the coating, although the corrosion potential slightly shifted to more negative values, but the corrosion rate decreased, which can be related to more activity of cobalt with respect to nickel. A decrease in grain size of the coating increased the corrosion rate and shifted the corrosion potential to more positive values.