Investigation of the Effects of Alumina Nanoparticles on the Corrosion Resistance of Ni-W Coatings Prepared by Electrochemical Deposition

Ni-W alloy coating is a novel coating that can be used as an environmentally safe substitute to hard chromium coating. To improve corrosion properties of this coating, nanocrystalline and amorphous Ni-W coatings containing Al2O3 nanoparticles were electrodeposited from three different baths by direct current method. Scanning electron microscopy, EDS and X-ray diffraction analysis were used to characterize the coatings, and electrochemical impedance spectroscopy and electrochemical polarization measurements were carried out to evaluate the corrosion behavior of nanocomposite coatings. It was found that nanoparticles can codeposit with the the Ni-W matrix; however the amount of embedded nanoparticles depends on bath chemical composition. In addition, nanoparticles can result in a more compact coating with fewer defects. Electrochemical measurements reveal that nanoparticles have the capability to improve corrosion resistance of Ni-W alloy coatings, though the levels of improvement depend on coatings structure which is affected by bath chemical composition.