Electrochemical Deposition of Ni-W Crack-Free Coatings

The main features of electrochemical deposition of coatings based on Ni-W binary alloy in the pulse current mode using pyrophosphate electrolytes were studied. Two electrolytes with a pH of 8.7 and 9.5 were used. The deposition was carried out with the current density varying in the range of 0.01-0.1 A center dot cm(-2), and the duty cycle (the relative pulse duration) was changed within the range 20-100%. The surface morphology and elemental and phase composition of the coatings were studied by scanning electron microscopy, energy-dispersive X-ray microanalysis and X-ray diffractometry. The experimental conditions allowing us to achieve the maximum Faradaic efficiency and W content in the coatings were determined. It was found that the pulse current mode enabled the fabrication of crack-free coatings with a thickness greater than 6 mu m.