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-----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
2001
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? Please send a picture!
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.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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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 any site to be an expert opinion.
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 eyesore.
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
Hi Kristine
You asked a question, but you may actually have answered it for us by being the 2nd person to relate the same problem 🙂
Researching the topic a bit we find that the problem is not exactly rust, but it's a problem nevertheless. The tannins in mahoghany react with zinc, causing dark stains.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
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