Effect of rare element cerium on the morphology and corrosion resistance of electro-less Ni-P coatings

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.

Keywords

• electro-less Ni-P coatings
• rare element cerium
• microstructure
• phosphorus content
• corrosion resistance
• porosity