The co-deposition of nickel and zinc with or without reinforcement of nanometer diamond powder were successfully manufactured by the method of electro-plating process on the carbon steel substrate. The variables investigated within this research work include the additions of ZnCl2, anode current density (ACD) and cathode current density (CCD), PH value, plating temperature, and the concentration of nanodiamond powder in nickel sulphamate plating solution. It revealed that g (Zn21Ni5) phase could be plated on the specimen surface with the thickness of 30 ¢Ggm for 1 hour plating time. The diamond powder used in this research work had an average size of 25 nm and concentration of 2 g/l to 20 g/l in the solution. After experiments, the corrosion resistance of these co-deposited plating layers was tested by the salt spray (fog) testing procedure for 0.5 to 30 days. It was found that the pure Ni-Zn alloy without co-deposited with nanometer diamond powder exhibited three times of corrosion resistance than that of with reinforcement of nanodiamond powder. The structure, surface morphology and the cross section of plating layers were examined by the x-ray, SEM, and optical microscope. The distribution of chemical compositions of plating layers was analyzed by the energy despersive analyzer of x-ray (EDAX) as well.