Why can element gallium be obtained through the electrolysis of sodium metagallate

In the textbook element gallium is produced by the electrolysis of sodium metagallate , which is obtained as the leftover solution of the alkali treatment of bauxite .


But why is the metagallate **anion** , negatively charged , going to be reduced on the **cathode** , which is also negatively charged ? Won't the Coulomb repulsion prevent the reaction ?


Or generally can an anion be reduced on the cathode ?
We shall use the iron anode in the electrolysis treatment of Cr(VI) waste water to have chromium reduced in the solution by **ferrous ion** rather than the electrons on the **cathode** ,which is unnecessary if bichromate can be reduced directly in the electrolysis .




Anions travel away from a cathode just partially, until there is built the counter potential gradient due charge displacement. When both gradients cancel each other, the migration stops. That happens when there is no ongoing electrolysis, e.g. if too small external voltage is applied.


When there is ongoing electrolysis, the balance is continuously disturbed, forming an additional charge displacement electrostatic gradient leading to continuous ion migrations.


So there are anions at the cathode and cations at the anode and can be reduced or oxidized.


Note that chromium electroplating is done with $\ce{Cr^{VI}}$ , not $\ce{Cr^{III}}$, reportedly because the latter is often kinetically inert.


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