Influence of Constant Magnetic Field on the Electrodeposition of Cobalt and Cobalt Alloys

The paper presents a study of the effect of constant magnetic field (CMF) on the basic processes of Co-Mo, Co-W, Co-Mo-W alloys and Co electrodeposition. The applied research methods included scanning electron microscopy (SEM), energy dispersive X-ray (EDX) microanalysis, cyclic voltammetry (CV), coulometry (C), scanning tunneling microscope (STM) and X-ray diffraction (XRD). SEM images of Co-Mo, Co-W, Co-Mo-W alloys revealed numerous fractures on the samples surface, formed as a result of residual stress during alloy deposition without CMF. In CMF such fractures disappeared. Under CMF conditions some crystal planes were deflected at angles ranging from 15 to 20°. The exposure to CMF caused also an increase of the volume fraction (by about 10 % by volume) of the dominant phase in the alloys. The reason for these changes was the fact that the Lorentz force, generated in CMF, caused the magnetohydrodynamic (MHD) effect. This induced movement of the electrolyte. The Nernst diffusion layer was depleted, whereas a new Navier-Stokes hydrodynamic layer appeared, which determined the velocity of electroactive molecules flow to the working electrode under CMF conditions.