Galvanic corrosion also known as bimetallic corrosion is a type of corrosion that occurs when two dissimilar metals are in contact with each other and exposed to an electrolyte, such as water or an acid. In this process, one metal acts as the anode and the other as the cathode.
In galvanic corrosion, the anodic metal corrodes because it is more reactive than the cathodic metal. This occurs because of the difference in their electro chemical potentials, which is
also known as their galvanic potential. When two dissimilar metals are in contact, an electrical potential is created between them, and this potential difference drives the electrochemical reactions that lead to corrosion.
Cause of Galvanic Corrosion
The cause of galvanic corrosion is the electrochemical reaction that occurs between two dissimilar metals when they are in contact with each other and exposed to an electrolyte, such as water or an acid. This reaction occurs due to the difference in the electrochemical potentials of the two metals.
Prevention of Galvanic Corrosion
Galvanic corrosion can be prevented or minimized by several methods, including:
- Use of similar metals: Using similar metals for both the anode and the cathode can prevent galvanic corrosion. For example, when connecting two metals together, use metals of the same type, or use compatible alloys that have similar electrochemical potentials.
- Isolation of metals: Isolating dissimilar metals from each other using insulating materials can prevent direct contact between them and reduce the chance of galvanic corrosion. This can be done by using gaskets, coatings, or insulating tapes.
- Cathodic protection: Cathodic protection involves connecting a sacrificial anode, such as zinc or magnesium, to the metal that needs to be protected. The sacrificial anode will corrode preferentially, protecting the metal from galvanic corrosion.
- Coatings: Applying coatings, such as paint or a plastic film, to the metal surface can prevent direct contact with the electrolyte, reducing the likelihood of galvanic corrosion.
- Corrosion inhibitors: Adding chemicals, such as inhibitors or passivators, to the electrolyte can help to prevent or reduce galvanic corrosion.
- Design considerations: Designing structures or equipment with galvanic corrosion in mind can help to prevent it. For example, avoiding the use of dissimilar metals in joints, using insulated fasteners, and avoiding stagnant electrolytes can all help to reduce the risk of galvanic corrosion.
By taking appropriate preventive measures, galvanic corrosion can be minimized or eliminated, leading to longer-lasting and more reliable structures and equipment