plating, anodizing, & finishing Q&As since 1989
Galvanized Nails are rusting in our wood storage buildings and decks
Q. Our company builds storage buildings and gazebos. We have always specified galvanized nails for their construction but lately are having problems with them. We recently had a large barn built for a customer. The subcontractor supposedly used galvanized nails, but now the customer is complaining that all the nails are rusting. We also had this problem with another subcontractor that did a deck for us. Are these contractors buying cheap nails? What is the real story on galvanized nails -- should they rust or not?Joy Kirkpatrick
- Fayetteville, North Carolina
A. Galvanizing means dipping in molten zinc. It is considered a functional finish rather than a decorative finish, so the appearance should probably not be guaranteed to be rust-free. There can be a brown color long before any meaningful corrosion is taking place, and some galvanizers even pride themselves on the claim that this brownish zinc-iron alloy is a feature.
But unfortunately, I can't really give you a good answer. Certainly it is very possible that the contractors are using cheaper, poorly inspected nails which may lack full zinc coverage so that they begin to rust immediately. You might be able to find additional info at www.galvanizeit.org.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
P.S. added in 2012: Another possible issue with wood decks, and any pressure treated wood, is that the ACQ pressure treated wood of today is far, far more corrosive to metal than the CCA pressure treated wood of just a few years ago. Please see thread 58799.
A. My guess is the nails are plated and not galvanized. They look shiny instead of ugly grey. I suspect that they had the absolute minimum amount of zinc on them and the hammer blows actually broke thru the plate. If the carpenter used a framing hammer (which typically has a very rough surface) it becomes even more probable. If you do not want any possibility of rust, specify stainless nails. They do cost quite a bit more unless bought in a large quantity.James Watts
- Navarre, Florida
A. Hi from new zealand.
o.k., I gotcha on this!
Regarding the problems of galv. nails rusting ... the answer is it's reacting with the timber treatment chemicals ... i.e., the Tanalise process. So that's my answer to you.
Another reaction process comes from hot water coming out of a copper hot water cylinder vent onto galvanised roofs ... it too rusts like mad; now you learn something every day.
- oamaru, new zealand
July 28, 2009
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