Electrodeposition of Ni-RuAl composite coating on steel surface

The present work aims to prepare Ni-RuAl composite coatings from Watt's solution containing suspension of single-phase powder of the intermetallic compound RuAl. The chemical composition, phase structure and surface morphology of pure Ni and Ni-RuAl composite coatings were investigated using energy dispersive analyzer system (EDX), X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The microhardness and oxidation resistance of Ni-RuAl composite coatings in comparison with pure Ni were evaluated. The corrosion behavior for both Ni and Ni-RuAl deposits was also evaluated by polarization curves in 3.5% NaCl solution at room temperature. The results revealed that the content of RuAl in Ni matrix is a function of applied current density and concentration of RuAl powder in the plating bath. Moreover, the presence of RuAl improves the oxidation resistance of Ni coating. The corrosion resistance of the Ni-RuAl coatings is superior to that of the Ni coating. The microhardness of composite coatings increases with the increasing content of the RuAl particles in the coatings. (C) 2008 Elsevier B.V. All rights reserved.