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Galvanic action between HDG & SS

We are involved in a job that requires us to attach 40" hot dipped galvanized (HDG) Unistrut to the concrete soffet of a tunnel we fitting up to run light rail trolley cars. The original spec had us attaching HDG strut with HDG anchors. Well the anchor size changed when we added the galvanizing so much that we could not get the anchor in the hole. We tried upsizing the bit but it became too sloppy. I asked the question if we could use Stainless Steel (SS) and was told OK, now after all the strut is hung another group is asking the question. Any help would be greatly appreciated.

Peter Dyer
- Boston, Massachusetts
2003

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I would expect you to get preferential corrosion of the galvanised Unistrut in the area where the two come into contact. The extent and rate of corrosion will be dependent on the environment. A solution may be to have an electrical insulator between the stainless steel and the galvanised Unistrut.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2003

It is OK, as long as the HDG was not damaged during the installation.

Len Wang
- Greenbelt, Maryland, USA
2003