EVALUATION OF ELECTROLESS NI-P AND NI-P NANO-COMPOSITE COATINGS' PROPERTIES

Abstract

SiC and SiO 2 nano-particles were co-deposited with electroless NiP coating onto API-5L-X65 steel substrates with 7g/L load of nano-particles in the bath at pH 4.6 ± 0.2 and temperature of 90 ± 2°C. The hardness and corrosion resistance of the composite coatings were measured using micro-hardness, polarization and electrochemical impedance spectroscopy techniques, respectively. Moreover, the structure of the composite coatings was investigated by means of X-ray diffraction (XRD) technique, while their morphologies and elemental compositions were analyzed using a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). Results showed that co-deposited nano-particles caused an increase in the hardness of the composite coatings. Corrosion tests showed that addition of nano- SiO 2 particles improved corrosion resistance of electroless Ni - P coatings in salty atmosphere but addition of nano- SiC particles decreased, due to the agglomeration of SiC nano-particles together with an increase in the porosity of the composite coatings.