Definition - What does Activation Polarization mean?
Activation polarization is the potential difference beyond the value of equilibrium needed to generate currents depending on the energy activation of a redox reaction. It is the activation energy that is required to have electrons transferred from electrodes into analyte.
Activation polarization is also known as electron transfer.
Corrosionpedia explains Activation Polarization
Activation polarization refers to the factors that are part of almost all electrochemical reactions inherent to kinetics. One typical example is hydrogen gas evolution. This type of reaction is simple and the rate of hydrogen ions' transformation to hydrogen gas functions in numerous factors like the transfer rate of electrons into ions of hydrogen.
Different metals have wildly varied electron transfer rates. Consequently, the hydrogen evolution rate of various metals vary significantly. This type of polarization is commonly caused by formation of a hydrogen reaction as well as cathode surface evolution.
Activation polarization determines the voltage or potential difference between the potential where the redox reaction is observed and the identified reduction potential. This happens in electrolytic cells that necessitate higher energy to force a reaction.
This is also observed in the polarization of galvanic cells, meaning there is less recovered energy, which is beneficial in identifying current density where the overpotential is taken.
This electrochemical reaction goes through various successive steps and is controlled by the slowest step in the process. In this case, the energy barrier must be overcome to proceed with the process. The needed activation energy for rising above the barrier makes changes to the electrode potential.
Any deviation from activation polarization equilibrium can result in deviation or corrosive effects.