Investigation Of The Corrosion Resistance Of Ni-Co Alloy Plated By High Frequency Pulse Currents

By restraining concentration grades of discharge ions(that is,electrodeposited ions) Within the liquid layer on the surface of the cathode,pulse plating has attenuated real thickness of diffused layer.Then it also reduced the concentration polarization during the cathode process,increase the limiting diffusion current density of cathode and gain the higher value of cathode polarization within the range of working current density. Since the value of cathode polarization increase,it will need a smaller work of nucleation,then the probability of nucleation and the number of crystal nucleus increased,the electrodeposited coating produced in these conditions will have a compact surface,a low porosity and refined crystals which caused small angle boundaries and in the end resulted in augmentation of materials performance such as hardness,corrosion resistance and etc.The corrosion resistance of Ni-Co alloys deposited by high frequency pulse current has been studied in 10wt.%NaOH,15wt.%H₂SO₄ and 3.5wt.%NaCl solution.The morphology of the alloys in 10wt.%NaOH,15wt.%H₂SO₄ and 3.5wt.%NaCl solution before and after were analyzed by scanning electron microscope(SEM).The effect of pulse parameters and the ionic concentration of cobalt in the electrolyte on the corrosion resistance of Ni-Co alloys were studied.The X-ray diffraction(XRD)was used to determine metallic phases.These studies indicated that pulse alloys were carried out to obtain compact and uniform surfaces,which appear to be cystiform in growth and exhibit better corrosion resistance in 10wt.%NaOH,15wt.%H₂SO₄ and 3.5wt.%NaCl solution in comparison to DC Plating.The pulse parameters and the ionic concentration of cobalt in the electrolyte influenced the corrosion resistance of Ni-Co alloys.The increasing of cobalt content in alloy deposits reduced the corrosion resistance of Ni-Co alloys...