The structure and properties of electroless Ni-P and Ni-Mo-P deposits

Abstract

The structure and properties of electroless Ni-P and Ni-Mo-P alloys, including the as-plated and annealed deposits, on the aluminum alloy 5052, have been investigated to evaluate the corrosion resistance, thermal stability, electric conductivity, and mechanical characteristics of the coating assemblies. The corrosion behavior of the obtained deposits was examined in a 0.5M H 2SO4 environment. The crystal structure of the electroless Ni-based alloys was analyzed by X-ray diffraction (XRD), and the surface morphology and microstructure of Ni-P and Ni-Mo-P alloys were examined by field emission scanning electron microscopy (FE-SEM). The experimental results indicate that the corrosion rate of the Ni-Mo-P coating produced at 70° and pH 7.0 is almost equals that of the Ni-P film in a 0.5M H2SO 4 environment. It is also found that the Ni-Mo-P ternary alloy reveal excellent thermal stability after annealing at 400° for 1 hr. The electroless Ni-Mo-P deposits have a potential to apply to precision mould and surface metallization of substrates, based on the excellent performance of the ternary alloys.