MAGNETIC-FIELD EFFECTS ON NICKEL ELECTRODEPOSITION

The effects of a superimposed magnetic field B on the structure of nic kel electrodeposits prepared from a quiescent Watts solution were stud ied by scanning electron microscope and transmission electron microsco py investigations. It was observed that B can induce a change of the s urface morphology and of the preferential growth direction of the nick el grains. In the absence of organic inhibitor, it is shown that these effects result from an inhibition of nickel-electrocrystallization in relation to the mass-transport enhancement of HC ions promoted by the magnetic field. The phenomenon is much more important in the presence of a strong inhibitor such as 2-butyne-1,4-diol, the activity of whic h is also under mass-transport limitation. The presence of the magneti cally induced convective flow is directly illustrated by the perturbat ions of the relief of the deposit in the vicinity of attached bubbles. These results demonstrate that most structural modifications of nicke l electrodeposits observed in the presence of a magnetic field are con sequences of convection phenomena induced by a magnetohydrodynamic eff ect.