THE RELATIONSHIP BETWEEN THE GROWTH-RATE OF HYDROGEN BUBBLES AND THE DURATION OF THE INDUCTION PERIOD IN THE ELECTROWINNING OF ZINC FROM SULFATE ELECTROLYTES

As a result of detailed polarization, volumetric and optical, in situ investigations of the growth rate of hydrogen bubbles during the electrowinning of zinc from Ni2+-containing sulphate electrolytes and in the presence of an inhibitor, a relationship has been established between the shape of the hydrogen bubbles and the duration of the 'induction period'. It has been found that during the 'induction period' hydrogen bubbles alter their shape from spherical at the beginning to cupola-shaped at the end, thus increasing by 10-12 times the extent of the screening of the cathode surface beneath. Experimental confirmation is presented for the validity of the previously proposed [1] physical model for the nature of the 'induction period'. © 1990 Chapman and Hall Ltd.