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topic 9870

Galvanized nails rusting in Mahogany porch floor


Q. I used a galvanized hot dipped nail from Georgia Pacific in an application of a covered porch floor of mahogany. They began rusting immediately after painting with "deck Paint oil" and continued to get worse until 95% of the nails were rusted. Georgia Pacific has told me that galvanized nails are not rust resistant! And handed the matter to their attorney.

What do you know about galvanized nails?

Michael Cortese
- Bay Head, New Jersey, USA


A. I'm having a hard time picturing this porch, Michael. It's built of mahogany, but with exposed nail heads? Will people's shoes eventually wear the galvanizing off, or are the nail heads recessed? They are recessed, but no wood filler in the holes? Send a picture! (I'm not sure how well the "deck paint oil" will adhere to a galvanized surface as opposed to a wood surface).

What do you mean by 'rust'. If you mean the orangish-brown corrosion products of iron & steel ('red rust'), I would agree that I would not have expected a galvanized nail to rust under these conditions--that's why it's galvanized. But if you are objecting to white spots from the white corrosion products of zinc ('white rust'), well, the way galvanization works is through cathodic protection, i.e., the zinc corroding preferentially to the steel. Good luck and please clarify if you can.

P.S. You only get an expert opinion by going to your own attorney and having him/her retain an expert, so please don't consider anything you may read on this site to be an expert opinion.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

(2002) -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. This past spring, we had a Mahogany deck built. The contractor chose to use Hot-Dip Galvanized nails to fasten the floor boards. Only a few weeks had passed, and we started to see black stains around each nail site. The staining has continued to worsen, and has turned the beautiful finish into an eye-soar.

I asked other people who had experience in working with Mahogany - another contractor and a furniture maker. They both indicated that one should never use galvanized products on Mahogany, as there is a chemical reaction between the wood and the fastener which will create these stains throughout the wood.

I am looking to confirm this - can you comment, or provide any additional information?

Kristine Hentschel
- Grafton, Massachusetts

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