How to Prevent Galvanic Corrosion

Galvanic or dissimilar metal Corrosion is a electrochemical process where one material corrodes when comes in contact with another material. You can check more about Galvanic corrosion here. Galvanic corrosion can be prevented through following methods.

Insulation of dissimilar metals

Presence of conductive media between two metals is primary requirement for galvanic corrosion. Where ever possible insulating dissimilar metals can completely stop electrochemical process or corrosion.

Selection of materials closer in galvanic series

Selection of material shall be done based on anodic index value. Lower the difference in anodic index values, higher will be galvanic corrosion resistance.  You can refer Anodic Index table here.

Sacrificial or Protective Metallic Coating

More anodic metallic coatings can provide sacrificial galvanic corrosion protection to the base material.

As a result of higher anodic index of coating, galvanic corrosion will start from metalic coating. In another words metalic coating sacrifices itself to protect the base material.

One of the advantage of sacrificial coating is : Even damaged coating protects the base material.

Extent of corrosion protection depends on coating material and thickness. For example, 12 micron zinc plating over steel will provide more corrosion resistance compared to 8 micron coating.

Size of Cathode and Anode in dissimilar Metals

Smaller the surface area of the anode with respect to cathode, more will be the concentration of flow of electrons from anode to cathode. As a result, more will be the corrosion.
In another words, to improve rate of corrosion, avoid keeping small anodes in contact with larger cathodes.

Non Sacrificial Metallic and non metallic coating

Non-Sacrificial coatings such as powder-coating or paints works as a barrier and reduce galvanic corrosion. These Coatings are not as effective as sacrificial coatings.

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