Polarization (electrochemistry)
In electrochemistry, polarization is an effect that counteracts and lowers the efficiency of electrochemical processes. The mechanism is typically depletion of reagents causing concentration gradients in boundary layers or the formation of compounds partly passivating the electrode surfaces and having the effect (depending on conditions) of decreasing the output voltage of batteries, increasing the voltage required by electrolysis cells or lowering currents. It is a type of kinetic deviation from equilibrium conditions. It is usually distinguished from overpotential.
Importance in corrosion
As an electrochemical phenomenon it is of importance for corrosion, typically lowering corrosion rates. Increasing polarization of either the cathode or anode - usually by using corrosion inhibitors - helps reducing the corrosion rate.
Types of polarization
- Activation-reaction at metal-electrolyte
- Concentration-diffusion in electrolyte