Effect of alumina nanoparticles as nanocomposites on morphology and corrosion resistance of electroless Ni-P coatings

摘要

Electroless Ni-P-Al_2O_3 nanocomposite coating was obtained by adding alumina nanoparticles to the nickel electroless plating bath. Particles of ~74 nm in size were selected in order to study the influence of the particle incorporation to the coating properties. The composite coatings were heat treated at 200, 400 and 600°C for 1 h (60 min) and structural changes were evaluated by X-ray diffraction (XRD) analysis. Surface morphology of composite deposits has been investigated by scanning electron microscopy (SEM). Electrochemical impedance spectroscopy and potentio-dynamic polarisation method have been used to evaluate the coating performance before and after heat treatment. The Ni-P electroless coating contains 9-18 wt-%P while the alumina composite coating contains 8-30 wt-%P. The composite coatings, which contains alumina nanoparticles, exhibit better properties of hardness and corrosion resistance.