Why can oxidation and reduction both occur at the same electrode potential?

At any given electrode potential, both oxidation and reduction processes can occur simultaneously because the rate of each reaction is determined by the concentration of the reacting species and the specific electrode potential.1

While these processes happen at the same time, they often occur at different rates. The net current observed at an electrode is the difference between the rate of electron ejection (oxidation) and the rate of electron injection (reduction). When the electrode potential is adjusted such that the rate of oxidation exactly equals the rate of reduction, the system reaches a state of chemical equilibrium, a condition described by the Nernst equation.12

In complex systems, such as a corrosion couple, a metal may simultaneously undergo oxidation (dissolution) and reduction (such as hydrogen evolution) at the same potential. In these instances, the potential is established by balancing the anodic and cathodic currents of the competing processes.3