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 hav e been investigated at 30 degrees C. Periodic current reversal (PCR) has be en 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 constan t (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 e fficiency of the process as well as the amount of slime remaining on the su rface 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.