Erosion-Corrosion Behavior of Electroless Ni-P Coating on Copper-Nickel Alloy in 3.5 wt.% Sodium Chloride Solution

摘要

The present investigation concerns electroless Ni-P coatings prepared onto the copper-nickel alloy (CuNi 90/10) to enhance the erosion-corrosion resistance. X-ray diffraction technique (XRD), scanning electron microscopy, and electrochemical methods were utilized to study the heat treatment effects on the erosion-corrosion resistance and the physical properties of the coatings. The results indicated that both the as-plated and coating with post-heat treatment (PHT) showed much higher self-passivation ability and much lower current densities than that of the copper-nickel alloy (CuNi 90/10). XRD results showed that both the as-plated and coating with PHT had amorphous structure and the effect of PHT at 190℃ on the structure of Ni-P coating was not significant. Compared with coating with PHT, the as-plated exhibited lower erosion-corrosion resistance due to some small pits and cracks. The coating with PHT demonstrated significant improvement of erosion-corrosion resistance in 3.5 wt.% NaCl solution, which was attributed to better protective film, lower porosity of coatings, and high micro-hardness compared with Ni-P coating without PHT.