Effect of the Deposition Potential on Morphology, Nucleation, and Crystal Orientation of Nickel Electrodeposited

Abstract

The works reported in this paper deal with the effects of the electrodeposition potential on the morphology, the nucleation, and the crystallographic features of the nickel electrodeposited from a Watts-type bath. For this purpose, coatings electrodeposited at five different deposition potentials from –0.60 V/Ag/AgCl to –0.80 V/Ag/AgCl were investigated. The morphology of the coatings was studied using scanning electron microscopy, and the current transients were compared to the 2D and 3D theoretical models of nucleation and growth. Then, the diffractograms were plotted as a function of the deposition potential. The results showed that the coatings are uniform when deposited at –0.60 V/Ag/AgCl. The nucleation and growth of coatings all follow the instantaneous models in the potential window of study but switch from 2D to 3D at –0.65 V/Ag/AgCl. These different features of the coatings have been attributed to the hydrogen evolution reaction which represents up to 10 % of the total current at –0.80 V/Ag/AgCl. Besides, the calculation of the texture coefficient extracted from the X-ray diffraction data has indicated the plane (220) as the preferred crystal orientation. Also, the observation of the shifts of the peaks has demonstrated the presence of uniform stress in the electrocoatings deposited from –0.60 V/Ag/AgCl to –0.75V/Ag/AgCl. Above, tensile stress appears.