Effects of Low-Concentration Copper Sulfate on the Microstructure and Properties of Electroless Ni-P Coatings
In order to improve the surface quality and properties of nickel-phosphorus (Ni-P) coatings,a small quantity of copper sulfate (CuSO4·5H2O) was added to the electroless Ni-P plating solution to prepare Ni-P coatings. The surface morphology,composition and struc-ture of the coatings were analyzed using scanning electron microscopy,energy-dispersive spectroscopy and X-ray diffractometer. The effects of CuSO4·5H2O concentration on the microstructure,surface roughness,glossiness,hardness,wear resistance and corrosion resistance of the coatings were investigated. Results showed that when the concentration of CuSO4·5H2O was 0.1 g/L,the coating exhibited a dense,amor-phous nodular structure with the best corrosion resistance. At a concentration of 0.2 g/L,the coating had the best surface quality,high hard-ness and excellent wear resistance,but a small amount of microcrystalline Ni-Cu solid solution appeared in the coating,leading to decreased corrosion resistance. When the concentration of CuSO4·5H2O exceeded 0.2 g/L,the coating formed a mixed crystalline cauliflower-like struc-ture,and both the surface quality and corrosion resistance of the coating deteriorated with increasing CuSO4·5H2O concentration.
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