Structure and Electrochemical Characterization of Ni+W+Si Composite Coatings in an Alkaline Solution
Ni+W+Si composite coatings were prepared by nickel deposition from a bath containing suspension of tungsten and silicon powders. These coatings were obtained under galvanostatic conditions, at the current density of jdep. = 0.100 A cm-2 and at the temperature of 338 K. A scanning electron microscope was used for surface morphology characterization of the coatings. Chemical composition of the coatings was determined by EDS method and phase composition investigations were conducted by X-ray diffraction. Thermal treatment of obtained coatings was conducted in the air and nitrogen atmosphere. Electrochemical corrosion resistance investigations were carried out in the 5 M KOH, using potentiodynamic method. It was found that Ni+W+Si coatings after thermal treatment in the air are more corrosion resistant in alkaline solution than Ni+W+Si coatings after thermal treatment in the nitrogen atmosphere and as-deposited coatings. The main reason of this is presence of new phases, in particular NiWO4 and SiO2.
António Torres Marques, António Fernando Silva, António Paulo Monteiro Baptista, Carlos Sá, Fernando Jorge Lino Alves, Luís Filipe Malheiros and Manuel Vieira
M. Popczyk et al., "Structure and Electrochemical Characterization of Ni+W+Si Composite Coatings in an Alkaline Solution", Materials Science Forum, Vols. 587-588, pp. 815-819, 2008