Magnetic Field Effects on the Growth of the Diffusion Layer at Vertical Electrodes during Electrodeposition

Vertical electrodes were studied in a shallow vertical position (2-3 mm high) and in the deep vertical position (V ) where the electrodes were 20-30 mm high. In the shallow vertical position the convection limited the growth of the diffusion layer, generally resulting in a stable thickness at approx 60 s, the onset of convection becoming noticeable at approx 15 s. The concentration gradient which is found from the fringe bend by application of the correct constant was smooth and resembled the cathode over the anode (C/A) in form, but not extent either in thickness or concentration. At short times ( > 15 s) and casual comparison it is possible to mistake a convection-limited diffusion layer concentration contour (interference fringe) for an unlimited diffusion layer fringe. The application of a strong magnetic field produces a very different effect, even at short time, on these two electrochemical transport systems. The microcell used, which was also a Fabry--Perot type interferometer, has often been described. Briefly, the 90% reflecting glass flats were spaced at 2.0 mm by the two electrodes whose active exposed area was 62 mm exp 2 . The multiple-beam fringes formed by reflections from the flats had a finesse of approx 7. The light source was a nominal 1 mW He--Ne laser. This electrochemical system was analogous to a Cu refining or electrodeposition cell, Cu/CuSO sub 4 /Cu with 0.1M CuSO sub 4 at its natural p H. 12 ref.--AA