Effects of Low-Concentration Copper Sulfate on the Microstructure and Properties of Electroless Ni-P Coatings

Abstract

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 structure 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, amorphous nodular structure with the best corrosion resistance. At a concentration of 0.2 g/L, the coating had the best surface quality, high hardness 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 structure, and both the surface quality and corrosion resistance of the coating deteriorated with increasing CuSO4·5H2O concentration.

Keywords

• electroless plating; ni-p coating; copper sulfate concentration; microscopic structure; wear resistance; corrosion resistance