Avoid this mistake


This may be old stuff to those of you in wetter climates but something easily overlooked in dry AZ.
I'm furring out a bathroom wall before installing a vanity I built.
I was trimming some 2 X 6's to length on the chop saw and since they were ten footers and I don't have a support that long I pressed the Unisaw into service to support the long end. A handy cutoff of pressure treated lumber on top of the fence was just the right height.
I finished my cuts, hauled the lumber into the bathroom and called it a day. Unfortunately, the next day when I hit the shop I discovered that I had knocked the block of PT onto the saw tabletop and underneath was a (not so) nice rust spot.
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Wes Stewart wrote:

You have experienced the new ACQ treated lumber. It is extremely corrosive and this is what happens when the chemicals in it come into contact with unprotected metal. I did an experiment with it and found that after two months, there is significant deterioration of common nails, zinc coated bolts and anything else that is not stainless steel or double dipped hot galvanized.
--
Robert Allison
Rimshot, Inc.
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Would this have happened if the saw table had a fresh coat of wax on it? I'm not sure if the OP's saw was coated or not, but I'm curious just how corrosive the ACQ lumber is.
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Mike Pio wrote: ...

Yes, but probably not extensively overnight. Wax alone, however, is very hard to keep on a working table sufficiently that it doesn't show wear spots very quickly. Having a recently waxed surface would undoubtedly have helped in the short term, however.
I get splots in the summer simply from perspiration drops even in a very dry area.
The same thing OP observed can happen w/ less aggressive action w/ almost any framing lumber--it is almost universally wet enough to cause rusting of bare ferrous metal surfaces.
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Mike Pio wrote:

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Absolutely iot would with a fresh coat of wax. Wax is not a good water barrier.
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wrote:
[snip]

Not fresh---this is AZ so it doesn't need it often--- but it has been treated with Top Coat.
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Yes. Wax is for short-term turnback of liquids and corrosive chips. A green cherry or oak curl neglected overnight on even a well-waxed jointer table will leave its mark. Ask any turner.
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Robert Allison wrote: ...

Yeah, this is yet another case where imo the cure is worse than the disease... :(
Much other testing has shown the same thing, of course. I'm not convinced the double-dip galvanized will hold up for really long term, either.
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Actually any WET lumber will do this. 5 years ago I learned this with the old style WET PT lumber.
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On Mon, 22 Aug 2005 08:26:49 -0600, Robert Allison wrote

Good advice for any fasteners used on "wet" wood or wood that might become wet (i.e. sill plates)
Once the fasteners go away, so does the wall.
While renovating this old house, I came across may nails that were corroded to the point of "not doing squat". The occasional galvanized nail, though still corroded, looked very serviceable.
-Bruce
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Wes Stewart wrote:

Out of habit, I clear off the cast iron portion and pile up stuff on the laminate table board.
Dave
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Red oak loaded into the shop from the back of a pickup truck in a rainstorm has exactly the same effect. Didn't matter that the saw table was freshly waxed. Well, perhaps it wasn't quite as bad as your PT-induced mess, but it required a 20 minute cleaning.
Good luck with the bathroom project. I'm installing the vanity in our this morning. It was supposed to happen last week, but when laying things out, I neglected to properly account for the location of the cold water angle stop, and had to re-route the plumbing.
I'd rather level ipe with a scrub plane than sweat solder copper pipe. ;-}
Patriarch
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On Mon, 22 Aug 2005 12:04:06 -0500, Patriarch
[snip]

Thanks. This project started a long time ago. Something else always coming up, like rotator cuff surgery following too much hand sanding and three months of recuperation, et cetera...

I was REALLY "sweating" it when I had to change some plumbing buried in a concrete block wall. :-) That's part of the reason that I'm furring out instead of butting into the existing wall. Figured it was easier to hide it than to make it pretty. Plus I think the builder hired a crew of drunk Mexicans to lay up the walls. There isn't a plumb one in the house. Of course it's a Santa Fe style house so it's supposed to look like it's made of mud but when you start hanging cabinets, and so forth it's a PITA.
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