What is galvanic corrosion, cause of galvanic corrosion and prevention corrosion of galvanic corrosion

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.

The anode is the metal that corrodes more quickly, while the cathode is the metal that corrodes more slowly or not at all. The anode experiences oxidation, which results in the release of electrons, while the cathode experiences reduction, which involves the uptake of electrons.

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.

For example, if copper and zinc are in contact with each other in the presence of an electrolyte, such as seawater, the zinc will act as the anode and corrode more quickly than the copper, which acts as the cathode. This process can lead to the formation of pits or holes in the surface of the anodic metal, which can ultimately lead to the failure of the metal.

Galvanic corrosion can be prevented by avoiding the use of dissimilar metals in contact with each other, or by using protective measures such as coatings or barriers to prevent the electrolyte from reaching the metal surfaces. The use of sacrificial anodes, which are made of a more reactive metal than the material being protected, can also be used to prevent galvanic corrosion by sacrificing themselves to protect the more valuable metal.

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.

When two dissimilar metals are in contact with each other in the presence of an electrolyte, an electrical potential difference is created between them. This potential difference causes electrons to flow from the metal with the lower electrochemical potential (the anode) to the metal with the higher electrochemical potential (the cathode). This flow of electrons leads to an electrochemical reaction at the anode, resulting in the corrosion of the metal.

The rate of galvanic corrosion depends on several factors, including the nature of the metals involved, the surface area of the metals in contact, the distance between the metals, and the nature of the electrolyte. In general, the greater the difference in electrochemical potential between the metals, the more rapid the rate of corrosion.

To prevent galvanic corrosion, it is important to avoid the use of dissimilar metals in contact with each other. If it is necessary to use dissimilar metals, protective measures such as coatings, barriers, or sacrificial anodes can be used to prevent contact between the two metals or to provide a more reactive surface that will corrode preferentially to the more valuable metal.

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