# Controlling Current Density in Electrowinning Cell

What are the parameters which govern the current density in an electrowinning cell? What equations relate Current Density to the applied potential difference?

Is it simply just Ohm’s Law J = σE? Where does redox at the electrodes come into play, if this is the case?

• The above version of Ohm law is valid in the free solution only, and for large density range only approximately. The overall topic is complex and requires some knowledge of electrochemistry. – Poutnik Feb 12 at 4:37
• Do you have any recommended readings for Electrochemistry? – Joeseph123 Feb 12 at 5:55

The system is complicated by many nonlinear processes.

As the topic is electrode focused, the primary controlled parameter should be the electrode surface current density $$\sigma$$, especially on the depositing electrode.

the total coltage applied on the electrolytic cell is devided on several potential differences:

$$U_\mathrm{applied} = U_{td}(\sigma) + U_\mathrm{kin}(\sigma) + U_\mathrm{diff}(\sigma) + U_\mathrm{cond}(\sigma)$$

where the particular terms are

• electrode potential difference given by reaction thermodynamics

• electrode potential difference given by reaction kinetics

• electrode potential difference given by near electrode diffusion gradient.

• free solution potential difference controlling ion migration.

For practical reasons, I advice using empiric approach :

• either constant current power source, if applicable

• either manual voltage control, using visual ampermeter feedback.