Structural, Compositional and Corrosion Characterization of Ni-W Thin Films

Ni-W thin films are fabricated on an ITO coated glass substrate by varying the current density. Cyclic voltammetry is carried out to know the required range of deposition potential for the synthesis of thin films. The influence of electrodeposition parameters on composition, crystal structure, micro-strain and corrosion properties of the film is studied. The presence of diffraction peaks at 2 theta values of 43.9 degrees, 50.7 degrees, and 74 degrees corresponding to (111), (200), and (220) planes have confirmed the face centered cubic structure of Ni-W films. Additionally, the (110) and (101) diffraction peaks recorded at 2 theta values of 21.3 degrees and 30.4 degrees are attributed to the formation of Ni4W phase. The formation of homogeneous, compact and cauliflower like morphology is confirmed by high resolution FESEM. The corrosion behavior of the films is investigated using Tafel Polarization technique in a 3.5 wt % NaCl solution. Ni-W film deposited at a current density of -50 mA/cm(2) has shown corrosion potential of -276 mV and highest corrosion resistance of 1917 Omega-cm(2). The enhanced corrosion resistance of Ni-W alloy is caused by the preferential dissolution of Ni and the formation of a W-rich film on the surface, which prevented additional corrosion.