The key difference between anodic and cathodic polarization is that anodic polarization refers to the change of an electrode’s potential in the positive direction whereas cathodic polarization refers to the change of an electrode’s potential in the negative direction.
Anodic and cathodic polarization are two electrochemical techniques that are important in reducing the corrosion rate of a metal surface. Anodic polarization is the opposite of cathodic polarization.
CONTENTS
1. Overview and Key Difference
2. What is Anodic Polarization
3. What is Cathodic Polarization
4. Side by Side Comparison – Anodic vs Cathodic Polarization in Tabular Form
5. Summary
What is Anodic Polarization?
Anodic polarization is the electrochemical process of changing an electrode’s potential in the positive direction. This can be done by a current flowing across an electrode-to-electrolyte interface, similar to the electrode polarization that is associated with electrochemical oxidation or anodic reaction. That means, change in the initial anode potential results in a current flow that affects the area near the anode surface.
Generally, the term polarization is the change in potential from a stabilized state as the outcome of the passage of current. Also, we can define it as the change in potential of an electrode during electrolysis, similar to the process where the potential of an anode becomes nobler than the respective reverse potential.
The major use of anodic polarization is to measure and protect surfaces against corrosion. We can also use it to determine the potential regions where materials are susceptible to rapid corrosion. We can easily polarize anodic surfaces via forming a thin, impervious oxide layer. However, this film formation must be often helped with the addition of anodic corrosion inhibitors such as chromate and nitrite.
What is Cathodic Polarization?
Cathodic polarization is the electrochemical process of changing an electrode’s potential in the negative direction. This method of corrosion control may include changing the potential of either the anode or cathode or sometimes both. Therefore, this technique minimizes the loss of metal, and it can reduce the driving force of corrosion reaction. The protection from corrosion through this method can be obtained when the potential difference is reduced to a minimum value.
Figure 01: Cathodic Protection Markers on a Gas Pipeline
Notably, a cathodic reaction occurs when there is a certain potential at the cathode. Here, hydrogen gas bubbles from the cathode which indicates a reduction reaction.
What is the Difference Between Anodic and Cathodic Polarization?
Anodic polarization is the opposite of cathodic polarization. The key difference between anodic and cathodic polarization is that anodic polarization refers to the change of an electrode’s potential in the positive direction whereas cathodic polarization refers to the change of an electrode’s potential in the negative direction.
Moreover, anodic polarization is an oxidation reaction whereas cathodic polarization is a reduction reaction. Anodic polarization is used to measure and protect surfaces against corrosion while cathodic polarization is used for protection against surface corrosion when the potential difference is reduced to a minimum value.
The following infographic summarizes the difference between anodic and cathodic polarization in tabular form.
Summary – Anodic vs Cathodic Polarization
Anodic polarization is the opposite of cathodic polarization. The key difference between anodic and cathodic polarization is that anodic polarization refers to the change of an electrode’s potential in the positive direction whereas cathodic polarization refers to the change of an electrode’s potential in the negative direction.
Reference:
1. “Anodic Polarization.” Anodic Polarization – an Overview | ScienceDirect Topics, Available here.
2. “What Is Anodic Polarization? – Definition from Corrosionpedia.” Corrosionpedia, Available here.
Image Courtesy:
1. “Gas Mains cathodic protection markers, Wellington Street, Leeds (12th April 2014)” By Mtaylor848 – Own work, (CC BY-SA 3.0) via Commons Wikimedia