What is the Difference Between Anodic and Cathodic Polarization?

The main difference between anodic and cathodic polarization lies in the direction of the potential shift and their effects on corrosion. Here are the key distinctions:

• Anodic Polarization: This refers to the change of an electrode's potential in the positive direction (above Ecorr). It is caused by current flowing across an electrode and results in an increase in the corrosion rate for non-passive systems (e.g., steel in seawater). For systems showing an active-to-passive transition, anodic polarization initially increases the corrosion rate and then causes a drastic reduction. Anodic polarization is used to measure and protect surfaces against corrosion.
• Cathodic Polarization: This refers to the change of an electrode's potential in the negative direction (below Ecorr). It is a reduction reaction, and in the context of corrosion, cathodic polarization always reduces the corrosion rate. Cathodic protection is the application of cathodic polarization to a corroding system.

In summary, anodic polarization is associated with oxidation and increased corrosion rates, while cathodic polarization is associated with reduction and decreased corrosion rates.

Comparative Table: Anodic vs Cathodic Polarization

The main difference between anodic and cathodic polarization lies in the reactions they involve and their purposes. Here is a table comparing the two:

Anodic polarization is used to measure and protect surfaces against corrosion, while cathodic polarization is used for protection against surface corrosion. Anodic polarization involves an oxidation reaction, whereas cathodic polarization involves a reduction reaction.