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Galvanic Reaction Between Dissimilar Metals

When using dissimilar metals in a fabrication project, precautions must be taken to prevent galvanic reaction. This occurs when two different metals are in contact in a corrosive or conductive environment and the current flow changes. When two dissimilar metals are involved, the reaction is called galvanic corrosion.

Why exactly does galvanic reaction occur? When one metal contacts with another, there is current flow between them. The current flow changes when dissimilar metals come in contact with each other: the corrosion rate of the active, or least corrosion-resistant metal, accelerates and the inactive, or more corrosion-resistant metal, decreases. The further apart the metals are on the corrosive scale, the stronger the galvanic reaction between the two. Similar metals have little effect on each other.

For example, aluminum is considered an active metal and stainless steel is considered inactive. In a corrosive environment, aluminum corrodes at a higher rate, but the stainless steel corrosion rate decreases. Corrosion can be caused by environmental disturbances such as weathering and atmospheric oxygen. Moisture is a key element affecting galvanic reaction.

The relative surface of dissimilar metals used in a metal fabrication project should also be taken into consideration. For example, using inactive metals as the main body of the project, joined by active connectors, could cause the joints or fasteners to corrode at a quicker rate. Best-case scenario would be to connect two sections of similar metals with fasteners also made of the same metal. If using similar metals isn’t possible, a compatible metal is the next best choice.

All Metals Fabrication employs the best, most experienced crews in the industry. Our metal fabrication craftsman are certified in their respective fields and dedicated trades professionals, so you can be sure you’re metal fabrication project is done right!

 

Photo from nasa.com.

 

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