Ask the Expert: How are fleets affected by galvanic corrosion?

March 31, 2015

It does not happen with all touch points of different metals, just between metals that are far away from each other on the electricrochemical potential series.

Q: How are fleets affected by galvanic corrosion?

A: It is a special type of corrosion that can occur where dissimilar metals are touching. These are galvanic corrosion hot spots. It does not happen with all touch points of different metals, just between metals that are far away from each other on the electricrochemical potential series. The worst and unfortunately the most common combination of dissimilar metals found are aluminum and stainless steel.

When in contact with each other, they act just like a battery where electrons flow from the aluminum to the stainless steel. In this scenario the aluminum will corrode extremely fast, leaving behind a white dust of aluminum oxide. Conversely, the stainless steel will be pristine and have extra life thanks to electrons the aluminum has so graciously donated. Yes, aluminum can "rust." Any metal can rust. Often, the rust or oxidation is not the red rust we are accustomed to see on steel, but a clear or white in color. These areas of galvanic corrosion are preventable by redesigning the hinges or fasteners, or placing non-conductive insulators between the dissimilar metals. Just painting over them is adding a longer fuse to a problem waiting to explode.

Information provided by: Sherwin-Williams Automotive Finishes