Hi,
Last fall we completed some renovations on our house which included some new porches and decks in the back of our house. The builder used one of the commercially available 1×4 mahogany decking species (probably not actually mahogany but meranti or similar I think) and stainless decking nails.
The distressing problem is that in the areas exposed to the weather the areas around the nail heads have stained black. Builder is vexed, we’re frustrated.
Ideas? Thanks!
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Replies
test the nails with a magnet..
also.. it could simply be the depression of the nail head is collecting water and the water alone is discoloring.. it might have nothing to do with corrosion
Testing with a magnet does not tell you if the nails are stainless, because there are grades of stainless that are magnetic.
the ones that will attract a magnet have enough iron in them to corrode..
and yes , i know there are different grades of SS
check out ( Google on )
Jamestown Distributors
for a good explanation of thte various grades..
McFeeley's also breaks it down for you
Mike Smith Rhode Island : Design / Build / Repair / Restore
Don't forget that it is "stainless steel" The key is that depending on the grade 316 -304 etc. some discoloration or even rusting may occur. Each grade is formulated for different strength, cost, and corrosion resistance.
it could simply be the depression of the nail head is collecting water and the water alone is discoloring.. it might have nothing to do with corrosion
What Mike said.
Also, if you are near the ocean, 304 stainless isn't sufficient.
Speak the truth, or make your peace some other way.
We are near the ocean and stainless, over time, will discolor slightly and even show signs of rust.
Grunge on.
Near the oecan, you should use type 316 stainless. 304 is OK elsewhere. Neither is a magnetic alloy.
Legit stainless nails will be 304 or 316, so anything a magnet sticks to is bogus. Given the bad metalurgy QC we see from the PRC and elsewhere, bogus stainless nails are a real possibility.
Try http://www.swansecure.com for good ones.
-- J.S.
all stainless steel will corrode under the right conditions, the "stainless" properties are dependant on a protective oxide layer on its surface, and under the correct conditions this layer can break down resulting in anything from a discoloration to a complete failure of the metal.If the wood is slightly acidic and there has been an ingress of water under the nail head it is possible that some corrosion has occurred.P.s I regularly use 304 stainless screws to fasten hardware to yacht decks with no adverse effects the trick is to have some sort of seal between the wood and the screw, varnish, anhydrous lanolin, PU sealant all work. The only time we'd use 316 is on the underside of the boat.Pp.s if you are by the ocean rinsing your deck off with some fresh water once a week to get rid of the salt will help stop any discoloration of the metalDuncan Miller
Boatbuilder/joiner
316ss is lousy for seawater. Oddly enough, when dealing with pumps, one of the toughest applications is seawater. Non metallics is about the only way to go.
I try not to use it. I much prefer silicone or aluminum bronze, but in certain instances it is best to use it to prevent electrolytic corrosion
I appreciate all the feedback. I'm in the Boston area and not near the ocean. I did save a box of nails so I have samples - should I get them tested? Which raises the next question: if testing shows they are not real stainless, who's liable? The builder, the local building supply co. that sold them?
if they're not..... then that's a shame.. but i don't think i'd waste a LOT of time pursuing liability
it might cost you more than the cureMike Smith Rhode Island : Design / Build / Repair / Restore
I agree that the depression is holding water. If the wood is black and the nail is shiny, it's probably not corrosion on the nail.
Another possibility is dirty nails, or for gun driven nails, tiny bits of the driver embedded in the nails. Take a glance at the following link under "installation."
Do the nail heads look shiny or are they also pitted/discolored?
http://www.swansecure.com/fasteners106/otherpages/page4.html
"Let's get crack-a-lackin" --- Adam Carolla
I have seen occasional staining when using SS staples and red cedar shingles. Never understood why, but it happens.
In addition to the aesthetic issue, you should be aware of the mechanical one, which is that the new pressure treated lumber will rust galvanized fasteners. So, I'd be concerned about the stains but I'd be really concerned about whether or not the nails are rusting out in the joists. If you have sample nails leftover it would be prudent to try a test... drive a few nails into joists under the deck, and watch what happens to them over time.
One other thing... sometimes a guy using a nail gun will either (1) forget to remove the clip leftover in the gun from the last job before starting the next job, or (2) accidentally mix two types of nails together in his truck or toolbox. I've done both. Either way you get the wrong nails somewhere, even if it's just a few.