Influence of Surfactants on the properties of electroless nickel boron (thallium and lead-free) coatings

Electroless nickel boron coatings were prepared from thallium and lead-free alkaline bath. The influence of surfactants on the properties of electroless nickel boron coatings was studied. Three surfactants namely sodium dodecyl sulfate, cetyltrimethyl ammonium bromide and 3-(N, N–Dimethylmyristylammonio) propanesulfonate were used. Morphology, microhardness, surface finish, topography and corrosion resistance of the coatings were evaluated. Electroless nickel boron coatings with addition of surfactant sodium dodecyl sulfate, cetyltrimethyl ammonium bromide and 3-(N, N-Dimethylmyristylammonio) propanesulfonate results in a smooth surface, with an average roughness value (R a ) of 0.220 µm for cetyltrimethyl ammonium bromide, 0.198 µm for sodium dodecyl sulfate and 0.174 µm for 3-(N, N-Dimethylmyristylammonio) propanesulfonate which are less than the R a without surfactant addition (0.256 µm). The deposits had a microhardness value of 590 and 743 HV in the as-plated and heat-treated conditions, respectively. With addition of sodium dodecyl sulfate, cetyltrimethyl ammonium bromide and 3-(N, N-Dimethylmyristylammonio) propanesulfonate, a significant improvement in the microhardness is observed. Potentiodynamic polarization tests were carried out in 3.5 wt% NaCl to determine the real anticorrosion performance of the electroless nickel boron deposits. The entire experimental procedure, the results achieved, and their investigation are presented in this paper.