Influence of periodic current reversal (PCR) on the passivation of anodes in the process of electrochemical refining of copper

Passivation of the electrolytic copper anodes in a refining electrolyte have been investigated at 30°C. Periodic current reversal (PCR) has been applied. The anode passivation time has been determined as a function of current density. The PCR variables were either the sum of the working (t w ) and reverse (t r ) current flow periods (105-630 s), when their ratio was kept constant (equal to 20), or different t w /t r ratios (10-40) and the sum (t w +t r ) constant (210 s). The effect of these parameters on the permissible current density (i pr ), below which the passivation does not occur, is analysed. Also the current efficiency of the process as well as the amount of slime remaining on the surface of the passivated anode have been investigated. The experimental results have been confronted with a corresponding equation derived for the assumed model of the process.