Aluminum and pressure treated NO-NO???


I had planned to use some aluminum angle pieces to tie down the front of some benches I made for my deck. When I looked at the tag on the PT wood it said "Do not use preserved wood in direct contact with aluminum".
The label says the wood is treated with Alkaline copper quaternary compounds. Anyone know what happens if Al is used with this??
Keeter
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"Salmo" wrote in message

In simplistic layman's terms, rapidly increased corrosion/oxidation of the aluminum due to chemical reaction with the ACQ.
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My guess is, the Al turns to a pile of white powdery gunk. The stuff is pretty corrosive.
The recommendations I've heard/read are to use stainless or, barring that, heavily galvanized (hot-dipped?) materials.
I seem to remember a _This_Old_House_ episode where they used heavily galvanized brackets and used a rubber sheet between the wood and the bracket. They even went so far as to use a piece of rubber hose slipped onto a hot-dipped galvanized lag screw to keep the screw from contacting the wood.
-j
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Great! The government makes a product that works as advertised to be taken out production. It is replaced by something that is known to react _unfavorably_ with accepted, cost effective, materials and practices forcing the industry to go to extreme lengths or radically increase the cost of doing business. All of this because people can't or won't learn to handle materials in a safe and responsible manner. Or, more likely, some litigious jerk found a lawyer to make a corporation pay for the jerk's mishandling of the materials.
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<previous quotes snipped...>

Did you also notice that the ACQ and CA products cost more than the old CCA? Reminds me of DuPont and freon.
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Larry Wasserman Baltimore, Maryland
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On Thu, 04 Aug 2005 15:37:34 GMT, snipped-for-privacy@fellspt.charm.net (Lawrence Wasserman) wrote:

There is a non toxic alternative check out http://www.timbersil.com / I saw it in the September TOH magazine in a one page blurb. Have not used it but if the cost the same and you can get it, why not? Other than silcia will eat your saw blades.
Mark
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Markem (sixoneeight) wrote:

Where can you buy the stuff retail?
The voicemailbox on their 800 number is full.
--

FF


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On 8 Aug 2005 10:50:45 -0700, snipped-for-privacy@spamcop.net wrote:

Wish I knew, local lumber yard is looking at getting some at my query. Did you try email or are you an impatient type like myself? Seems as though they are trying to lineup "treaters" as there are only two listed on the web site might be an opportunity to get in on the ground floor.
Mark
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Markem (sixoneeight) wrote:

False dichotomy. Both are true. ;-)
However the spammers have pretty much destroyed the usefulness of email for small to medium sized businesses.

Yes, maybe we should contact the licensed treaters to see who their customers are.
--

FF


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Why, of curse it does! Wasn't that part of the plan? Later, Beej
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Stainless steel, ceramic + epoxy coated or triple dip galv.Painted aluminum may be OK but check with your PT supplier first. Dave."Salmo"

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wrote:

Dissimilar metals will produce a mild electric charge- enough to cause one metal or the other to decay very quickly.
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Doubtful this would pertain here. Dissimilar metals as electrodes and an electrolyte, maybe. Like the aluminum window frames and steel screws they used on the US embassy in Cuba. Sits right at the shore in the salt air.
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No? Seems like a solid state battery to me. It's treated with an Alkaline copper compound, and then a dissimilar metal is pounded into it as an [anode?] (I always get anode/cathode mixed up) Put it in a little metal cylander and throw a volt meter on it, and I'd bet you'd get a reading- not a Duracell, to be sure, but a simple battery none the less.
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It's doubtful that a plain steel screw would be used. More likely that a galvanized steel would be used. And since zinc and aluminum have a relatively small potential difference, it's not a big problem.
todd
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Perhaps I was unclear. I was stating fact, not speculation. The aluminum was eaten away an inch or more in some directions. The rusty screws which had the protection of the aluminum were in good shape. Where the aluminum had ceased to be in contact, there was a modest pile of rust where the screw had been.
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I belive the problem here is that the wood will also retain a bit of moisture. This moisture, along with the "Alkaline" compounds will create an alkaline environment in contact with the aluminum. Aluminum dissolves in alkaline solutions. That's why they tell you never to use oven cleaning compounds on aluminum (strong alkaline solution). Understand, this won't happen overnight, but the situation is similar to using untreated steel angles for this job. Over time, they will both corrode.
BruceT

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