Abstract
This paper reports an experimental study on the microstructure and corrosion resistance of electro-less Ni-P coatings with increasing content of the rare element cerium (Ce). Surface morphology and the composition of the electro-less Ni-P coatings were studied by scanning electron microscope (SEM), X-ray energy dispersed analysis (EDS) and X-ray diffraction analysis (XRD). Hardness and Adhesive force are researched by a HX-200 Vickers diamond indenter micro-hardness tester. Furthermore, we study the adhesive force by using the Revetest scratch tester. We get the possession of Ce amorphous Ni-P coatings which has excellent properties in anti-corrosion. The effect of the rare element cerium concentration on corrosion resistance of the coatings was evaluated in the groundwater immersion test and porosity test, respectively. The results indicated that added little the rare element cerium into the plating bath increased the phosphorus content of the coatings, decreased the corrosion rates, it also decreases the porosity of the amorphous Ni-P coatings. The lowest corrosion rates of the amorphous Ni-P coatings in groundwater immersion test is 4.1 um · h-1, at the rare element cerium concentration of 0.12g · L-1.
Highlights
Electro-less nickel-phosphorus is a chemical processing method that the use of a suitable reducing agent in the solution of nickel ions are selectively activated catalyst surface of the substrate to deposit metallic nickel reduction of the surface coating
At the diffraction angle (2θ ) is 44.9°, the diffraction peaks appears, the peaks is the nickel (111) characteristic diffraction peaks. It indicates that the surface morphology of the coating which added in rare element cerium is amorphous structure
1) The Ni-P coatings contain the element of Ni, P and Ce, and the surface morphology of the coating is amorphous structure
Summary
Electro-less nickel-phosphorus is a chemical processing method that the use of a suitable reducing agent in the solution of nickel ions are selectively activated catalyst surface of the substrate to deposit metallic nickel reduction of the surface coating. As the phosphorous content increase in the Ni-P coating, its surface morphology changes from crystal structure to amorphous structure[5,6]. Amorphous electro-less Ni-P coating are formed in deposited process when the phosphorus content is more than 8 wt percent. Amorphous electro-less Ni-P coating has excellent corrosion resistance. The experiments, by added different concentration of rare element cerium, mainly study on the Ni-P coating of the surface morphology, hardness and adhesive force, the deposition rates, the phosphorous content and the corrosion resistance in a high morphology program
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