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  1. #1
    JeffTheGreat
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    Rust-proof Nails?

    What kind of nails should I use to repair an outdoor fence...
    also how can I paint over nails that are already rusting?

    -----------------------------------------------

  2. #2
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    RE: Rust-proof Nails?

    Were those two posts, the first, then the edit?

    Well either way, "welcome"

    I don't know what to do about painting over rusted nails...I hate to paint.

    If I was a'fixin' my fence (it's 3/4" horizontals with 4"x4" posts) I'd use 12p spiral galvanized nails or decking screws.

    What kinda fence are ya mendin'?
    Dave, from Indiana

    I am a great believer in luck. The harder I work, the more of it I seem to have.

  3. #3
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    RE: Rust-proof Nails?

    For a really super-PERMANENT fence, if it's pretty expensive, you could go with stainless-steel nails. They make 'em in all manner of different styles - distorted-shank & all.

    For anything else, galvanized (hot-dipped "silver" galvanized better than zinc-chromate "yellow" galvanized) is the ticket. They'll probably outlast most fences.

    If you're painting over nails (and, presumably fence), you can use "cold galvanizing compound", available in a spray can at your local welding shop (yellow pages).

    If youre NOT painting the fence, but want to protect the nailheads anyway... get some diesel in a little jar or coffee can & paint the head of each nail with it. The rusted nailhead will darken in color from it. The diesel will protect the nail from further rusting and collect a little dust so it, too, becomes virtually permanent. Used motor oil - especially thinned with diesel, kerosene, or mineral spirits, works pretty much as well. I did that to a little ding on my Jeep (do NOT ask!) where the paint was peeling away, and it's stayed rust-free for years in Vermont, where all the white ya see in winter ain't SNOW - it's SALTED ROADS.

    EDIT: Ahem. Sorry. Welcome. :) :) :)

    -- Tim --

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  4. #4
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    RE: Rust-proof Nails?

    What kind of wood is your fence made of, if it is treated wood, especially the most recent type you need special hot galvanized nails. Many packages of nails are now labeled as to whether they are suitable for treated wood, but it is best to check with somebody at the store.

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  5. #5
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    RE: Rust-proof Nails?

    I'm a structural engineer (which means this is the most conservative answer you're going to get) and this issue comes up a lot. The truth is that no one knows the long term affects of the latest wood treatment chemicals on steel. Tests show that the G90 galvanizing process (standard galvanizing process) can be completely broken down by treated lumbar in as little as three years. Hot Dipped Galvanizing or high end G185 galvanizing (which contains twice the zinc as a standard coating) begins breaking down before the three years is up. Stainless steel does not show any adverse reaction to the treated wood after three years (I'm referencing tests done by Simpson Strong-Tie that simulated three years of exposure, no one knows if the treatment, given enough time, would start to break down the stainless steel as well). So we always specify Stainless. On a commercial building the difference in price is usually less than a few thousand dollars. That isn't a big deal when compared to the price of an entire building. For a home project...my concern wouldn't be the failing of the nails. You'll see them deteriorating long before they fail. My concern would be the stains that the zink coating and the rusting of the nails would cause in the wood.

  6. #6
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    RE: Rust-proof Nails?

    Given that stainless steel is far higher in the galvanic series than copper (which itself is higher than zinc - explaining why zinc-coated nails would rust early in the presence of copper and water), I very much doubt that stainless steel nails will ever show any significant corrosion in pressure-treated wood.

    Heavily (hot-dip) galvanized nails, in most circumstances, should (at least theoretically) last a long time in pressure-treated woods. The principles are:

    1. PT is usually (not always) treated with one copper compound or another because of copper's natural fungicidal properties.

    2. Galvanic corrosion occurs when two dissimilar metals are brought into close contact with each other in the presence of an electrolyte (usually, in this case, water-borne salts or acids).

    3. Of those two dissimilar metals, the one lower in the galvanic series (worth looking up) than the other will corrode at an accelerated rate in such an environment.

    4. Zinc is ordinarily chosen as a rust preventative because zinc oxidizes quickly, forming a zinc-oxide layer that usually inhibits further oxidation. In addition, zinc is very very low in the galvanic series, so in the presence of nearly any other dissimilar metal it will corrode first, sacrificially, to prevent corrosion to the steel under the plating.

    5. Copper, while itself low in the galvanic series, is higher than iron, ordinary steel, or zinc. As such, its presence triggers galvanic corrosion of those metals.

    Ironically, steel is higher in the galvanic series than zinc. As a result, when the zinc coating on galvanized nails or other objects has been broken (through abrasion, cutting, or sometimes simply by a pinhole never closed in the plating process), the steel and zinc - together with an electrolyte such as water - will begin the process of galvanic corrosion of the zinc.

    In very short, the more perfect the plating's surface, the better protected the underlying steel. The heavier the plating's surface (hot-dipped is a far heavier coating than electrogalvanized), the better protected the steel.

    Stainless steels are very high in the galvanic series. 316 "Passive" stainless steel is only one lower than titanium, two lower than silver, three lower than gold. 304 "active" stainless steel is much lower (more subject to galvanic corrosion) in the series, lower than brass but higher than copper (the copper would corrode first), even higher than nickel and chromium (which are generally regarded as nearly "corrosionless" metals). So... speaking strictly in terms of galvanic action stainless steel should be quite safe from the copper in PT lumber.

    In terms of chemical protection, the chromium-oxide barrier layer that forms on stainless steel should be quite safe from any of the copper-bearing compounds used in pressure-treating lumber. Chemically, the zinc-oxide barrier layer on galvanized nails is also safe.

    A fence, of course, or anything else built in the outdoors and warranting the use of pressure-treated wood in the first place, is very likely to see a fair amount of moisture - from rain, from dew, splashing puddles in the road, sprinkler irrigation of lawns, washing, etc etc etc. They basically get WET... and it's in the wet that we see galvanic corrosion.

    I'd think that the "perfect" fasteners for pressure-treated wood would be... solid copper. There would be zero galvanic corrosion, and copper is chemically very safe from itself, and copper is highly environmentally stable because of its own copper-oxide barrier layer. Unfortunately, copper is also very SOFT - a problem plaguing most stainless-steel fasteners, too; nails made of the stuff are VERY prone to bending if they're struck less than perfectly, and screws made of it are as likely as not to strip while being driven. Strictly MECHANICALLY, the galvanized fasteners are far superior.

    All this changes if the fence is painted wood instead of PT, though. :)

    EDIT: DANG. I forgot to address Principle #6, that of saturation.

    6. As heavily zinc-plated fasteners corrode, the zinc that corrodes away doesn't simply vaporize; it dissipates into the surrounding wood. In doing so, it saturates that wood, displacing copper. As this happens, the remaining zinc plating is better and better protected from further galvanic corrosion.

    -- Tim --

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  7. #7
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    RE: Rust-proof Nails?

    Wow, it looks like you've covered everything. I can't make the concept of protecting steel any more clear than that last post and so I won't even try. All I would like to add (other than complementing Tim) is to talk a little more about the harmful affects of damaging the zinc galvanizing coating. If you scratch off that coating, typically we see that happening in areas where there is welding but the same result can come from a screw driver slipping on the head of a screw, you expose the steel and you lose most of the benefits derived from the zinc coating. In fact, I had teachers in school argue that you can do more damage by scratching the coating than you could by not having the coating in the first place. The solution is to have zinc rich paint on hand when you're using galvanized nails or screws. Simply touching up the galvanizing coating, cover any of the scratches a hammer or screwdriver could make will really extend the life of the fastener.

    Like I said in my first post, this really takes the steel coating discussion way beyond the backyard fence and into the realm of proper wood building construction. It's probably way more than you need to know, but everything Tim said is accurate and, if you've followed the last couple of posts, you're up to date on the issue at a professional level.

    On a personal note, I'm obviously a new comer here (this being my third post and all) as well as being a newcomer to the woodworking hobby. I've enjoyed reading your discussions and I've really enjoyed the fact that I could make a couple of posts on a topic that I actually know something about. Thank you all for all the information available on this site, it really has helped a newbie.

  8. #8
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    RE: Rust-proof Nails?

    Well, we're surely glad ta' have you here - both in the forum & in the circle of fellow woodworkers. :)

    Excellent point about the damage - that even applies to clumsy hammer use, and is an excellent reason not to salvage used galvanized nails or screws except for indoor purposes.

    Yeah, I know. How cheap can ya get, right? Been there, done that, though. :)

    -- Tim --

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  9. #9
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    RE: Rust-proof Nails?

    shish, a bunch of rocket scientists trying to nail a fence board up. :P

  10. #10
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    RE: Rust-proof Nails?

    Question for you, Jeff.

    Last Thursday, we welcome you to the forum. One week later, you're a "Charter Member". How much did that cost ya?
    Dave, from Indiana

    I am a great believer in luck. The harder I work, the more of it I seem to have.

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