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Hot-dip galvanized steel is well suited for use in a variety of environments and fabrications, and sometimes is placed in contact with different metals including, among others, stainless steel, aluminum, copper and weathering steel.

When two different metals are in contact in a corrosive environment, one of the metals experiences accelerated galvanic corrosion while the other metal remains galvanically protected. Relative surface areas of contacting dissimilar metals is also relevant in determining which metal exhibits accelerated corrosion. It is undesirable to have a large cathode surface in contact with a relatively small anode surface.


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michael mifkovic, California Department of Transportation

If a galvanized #6 reinforcement bar is in contact with a smaller #5 carbon steel bar in a concrete footing for a bridge structure (non corrosive soils), what sort of galvanic effects will occur to the black bar. Will accelerated corrosion occur in either of the bars (due to galvanic effects) if the alkalinity of the concrete lowers over time, or chlorides are introduced from the outside environment?

Alana Hochstein (AGA)

Yes, galvanic corrosion can still be a concern when hot-dip galvanized rebar and black rebar are embedded in concrete, but there are several methods to prevent it. For more information on this topic and how to limit the effects of galvanic corrosion in concrete, we have the following article on our website: https://galvanizeit.org/education-and-resources/resources/technical-faq-dr-galv/dissimilar-metals-in-concrete

Joseph Moser

If galvanized angles and bolts are used to reinforce and replace members on a weathering steel lattice tower that has fairly severe corrosion, is there a concern of accelerated corrosion of the galvanized items at the contact points?

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