Study on Influence of Zwitterionic Surfactant on the Surface Finish and Surface Morphology of Electroless Ni-B Coatings on Al 7075-T6 Alloy

Abstract

The influence of Zwitterionic - propanesulfonate surfactant on the surface properties such as surface roughness, surface morphology and microhardness of Ni-B coatings using electroless alkaline bath was reported in this paper. Ni-B deposits obtained from nickel chloride as the source of nickel and borohydride as the reducing agent at a pH of 11 and 12 and temperature 85 ± 2 OC. This study reveals that the Ni – B coatings were clearly influenced by the addition of surfactant propanesulfonate on surface roughness and surface morphology. Electroless nickel (EN) - B coatings with addition of surfactant has changed the surface morphology from non-smooth nodular appearance to a smooth surface with average roughness value 1.4μm, which is less than the Ra value of without surfactant 1.98μm. The hardness of the deposit increased with lesser concentration of the surfactant when compared to without surfactant addition. Surface morphology and composition of the Ni–B coatings was analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD).