Galvanic Corrosion – What is Galvanic Corrosion?

Galvanic Corrosion – also termed bimetallic corrosion, or dissimilar metallic corrosion is a very common painting fault.

Galvanic corrosion occurs when two dissimilar metals are in contact with each other as a result of the flow of very small electric currents. These metals must be in electrical contact and must be exposed to an electrolyte.

Metals that are susceptible to galvanic corrosion are known as anodes and metals that are resistant to it are known as cathodes.

Galvanic corrosion risk depends mainly on the chemical properties of the metals of an asset.

What is Steel?

Steel is a versatile material that is used in a wide range of applications. Steel is highly vulnerable to corrosion due to various different climatic conditions with red rust forming easily hence, the steel must be protected with Zinc coating to provide good corrosion protection.

What is Corrosion?

Corrosion is an oxidation process. Corrosion occurs due to the degradation of a metal, two mechanisms are involved, firstly an electrical circuit and secondly a chemical reaction.

What causes galvanic corrosion?

Due to various environmental factors steel is particularly vulnerable to corrosion with the formation of red rust.

When electric current flows between two dissimilar metals causes the more anodic metal to corrode as the current flows potential difference exists between the two metals it is an electrochemical process.

How to prevent galvanic corrosion

How to prevent galvanic corrosion? To prevent Galvanic corrosion here below are the most commonly used methods:

  • By using insulating material between the dissimilar metals such that they are not in direct electrical contact, by this method it effectively breaks the electrical circuit so the current cannot flow.
  • Also by select metals/alloys as close together as possible in the galvanic series.
  • By avoiding the un-favourable area effect of a small anode and large cathode.
  • One can insulate dissimilar metals wherever practical.


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