MLRem

Has anyone experienced significant corrosion of aluminum against ACQ (2005) pressure treated 2 by's. I have an overhead awning/pergola with an L-shaped aluminum gutter that was fixed directly to a 2x8. The gutter is heavy-gauged (1/8" thick) aluminum and painted/powder coated - but it is directly against the 2x8. I just did not think of the potential damage at the time and it would be significant work to get it down and put a roofing membrane behind it. The application is well above ground and in direct sunlight all day. Is the talk of copper leaching from PT lumber overblown and more related to in ground or wet locations - or should i be concerned and consider adjusting situation before it is too late?

greg24k

We have to know what area you from, so we can help you to figure the corrosion ratio for your area.

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parkers5150

i dont know how powder coated aluminum stands up against those chemicals but, they had no problem eating through hilti shot pins in 8 mos. it was this very situation that brought the whole industry dilemma to my attention. as far as you project being off of the ground, it is still subject to dew and rain no??? most people dont mind you fixing mistakes before they become a problem

mhillc

I done a job about 2 years ago for a guy who had a pergula over the front door. it was not built by me but the other contractor built it out of all pt and wrapped the 6x6 columns with aluminium. No lie i sware 6 months later i got the call to look at it and the aluminium was bubbling like someone put acid on it. And they say the acq is supposed to be less hamfull........HMMMMMM

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MLRem

I am in the northwest suburbs of Philadelphia - and yes it is subject to dew / rain, etc - but very well ventilated and as mentioned sunny location. No visibile signs of corrosion, but definitely this is a high contact situation.

Big Shoe

My Z-Max post bases are corroding all to hell. That first wave of that new ACQ lumber a few years ago was some nasty a$$ stuff. My ''exterior'' screws also coroded away and snapped in half.

VAviaCo

And this is what we use for bottom plates on wall framing.
Does everyone nail those with galvies now?

JamesKB2

I do! I use ACQ compatible fasteners wherever treated is used.

I know many, many don't, and wonder how many garages will have sill plates that are no longer fastened to studs or sheathing after a few years....

"Sorry your garage walls fell off foundation, I guess I should've used specialty fasteners...."

buildenterprise

Most of the ACQ around here is being replaced with much less corrosive MCa treated wood. Nowhere near as corrosive to aluminum. Still have to use ACQ for ground contact though, unless you special order higher concentration MCa product.

Big Shoe

For interior work we use borate treated lumber for all bottom plates and concrete walls, no special fasteners needed. The big box stores don't carry it around here that I know of.

neolitic

It takes 4-6 weeks to get it here,
and it isn't a great choice for decks.....
"Lumber treated with disodium octaborate tetrahydrate (DOT) historically has been used in protected, not exposed, locations because borate leaches from wood when the wood gets wet."

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(Sorry....it seems there really are dumb questions)

Glid

It has everything to do with Galvanic Attack. Aluminum is less noble (anodic) than the copper in the acq (cathodic). It's too bad we can't use a sacrificial metal like they do with boats! I am curious how long it takes a stainless(cathodic) screw to cause problems with the copper(anodic) in the wood for the same reasoning.

Ranzan

supposedly stainless will last longer than 30 years...... we will see ACQ is nasty stuff