Effect of surfactant on the fabrication and characterization of Ni-P-CNT composite coatings

Abstract

In order to disperse carbon nano-tubes in electroless Ni-P coatings different surfactants (sodium dodecyl sulfate (SDS) as anionic surfactant and Hexadecyl Trimethylammonium Bromide (HTAB) as cationic surfactant) were added to the electroless bath and their respective dispersing power was monitored by using ultra violet visible (UV–vis) spectroscopy method. Then Ni-P-CNT coating deposited, using optimum surfactant-to-CNTs ratio of proper surfactant. The morphologies of composite coatings were analyzed using a scanning electron microscope (SEM). Moreover, hardness and corrosion resistance of the applied composite coatings were measured via microhardness, polarization and electrochemical impedance spectroscopy (EIS) methods. Results showed that an optimum ratio of SDS can uniformly disperse CNTs throughout the electroless Ni-P coating, which yields the highest hardness. Corrosion resistance studies showed that the incorporation of CNTs can increase the corrosion resistance of Ni-P coatings due to the filling of pores and micro-holes, while decreasing the metallic area that is prone to corrosion attack.