How Current Density Affect the Cathode Deposit in Copper Electrowinning

How Current Density Affect the Cathode Deposit in Copper Electrowinning?

In the copper electrowinning process, the copper plating rate increases with increasing current density. However, excessive current density gives rough, nodular cathode deposits and decreased copper purity. Therefore, each plant chooses its current density as a balance between these opposing factors.

Maximizing current efficiency
Current efficiencies in modern electrowinning plants maybe around 90 %. The unused current is wasted by:
(a) anode/cathode short circuits
(b) stray current to the ground
(c) reduction of Fe3+ to Fe2+ at the cathode and re-oxidation of Fe2+ to Fe3+ at the anode.
High current efficiency is important because it maximizes copper plating rate and minimizes electrical energy consumption.
Some results of the effect of iron on the current efficiency at a total current density of 280 A/m2  are shown below.