Pulse electrodeposition and characterization of nano Ni-W alloy deposits

Pulse plating was employed to obtain Ni-W alloy nanodeposits from ammonical citrate bath. Effects of peak current density, pH, tungstate ion concentration and temperature on the cathodic current efficiency were studied. Ni-32.8 weight (wt)% of W alloy coating was obtained using optimized bath composition. Ni-W solid solution was found in the alloy deposit. Surface morphology studies revealed that the alloy surface was covered by long needle like crystals. XRD patterns of the electrodeposits showed only fcc (nickel) peaks. The hardness of the deposits obeyed Hall-Petch relation. Electrochemical polarization studies revealed that the corrosion potentials of nickel became nobler with W addition and corrosion current density values decreased. Electrochemical impedance studies found that, the increased charge transfer resistances suggesting decreased corrosion current density values. The capacitance values of the double layer decreased with W additions. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.