kirk.g
Well-known member
Ok, so what happens when you mix non galvanized metal with pressure treated?
pressure treated with non galvanized
- Thread starter kirk.g
- Start date
Jim Johnstone
Well-known member
The fasteners can corrode away very quickly. If you're talking about construction screws, when my buddy and I built his garage, we found the local Home Hardware building center had the green ACQ approved screws in bulk for less money than the boxed standard screws from Home Depot.
Falcon67
Well-known member
Same deal - if it touches treated lumber, it needs to be hot dipped galvanized.
petee_c
Well-known member
why?
rust is a perfectly acceptable colour......
I have a steel trailer that I use to bring my motorcycle places. I recently had to replace the floor (rotten, standard 3/4" ply after 10yrs). I used 1x6 planks for the floor. I did however paint the trailer with a coat of Tremclad primer and flat black paint after wirebrushing it.... I'll report back after the winter and let u know how it turns out.....
rust is a perfectly acceptable colour......
I have a steel trailer that I use to bring my motorcycle places. I recently had to replace the floor (rotten, standard 3/4" ply after 10yrs). I used 1x6 planks for the floor. I did however paint the trailer with a coat of Tremclad primer and flat black paint after wirebrushing it.... I'll report back after the winter and let u know how it turns out.....
ishiboo
Well-known member
why?
rust is a perfectly acceptable colour......
I have a steel trailer that I use to bring my motorcycle places. I recently had to replace the floor (rotten, standard 3/4" ply after 10yrs). I used 1x6 planks for the floor. I did however paint the trailer with a coat of Tremclad primer and flat black paint after wirebrushing it.... I'll report back after the winter and let u know how it turns out.....
Rust on structural steel is typically not a huge deal, it's surface rust and there is limited continual contact. It eats a small portion of the metal.
On brackets and screws, there is very little metal to work with, and they are in constant contact with the corrosive chemicals in the wood, so they do not last long. The brackets can quickly be eaten through, screws as well, and in rusting they can bleed all over.
Sundowner
Well-known member
many structural steels, such as Cor-Ten or ASTM A709 HPS Gr W are intended to rust via the alloying agents in the metal; they form a protective tight grain patina of rust, which then seals off the deeper metal from further corrosion. It's a popular choice for bridges since it doesn't require painting.
However, even Cor-Ten won't survice long term contact with ACQ lumber (Alkaline Copper Quaternary), which replaces the older arsenic treated lumber, which didn't have this problem. The alkalai base reacts with the Fe ions in the brackets and corrodes it to nothing.
Last I looked ,when building with ACQ lumber you MUST use triple dipped galvanized brackets (the part numbers in the Simpson catalog carry a "Z" suffix) for proper long-term durability. You can't miss them on the parts rack, the triple dip in the zinc makes them look almost chrome plated compared to the other stuff. They also cost buckets more than the other other stuff.
petee_c
Well-known member
I should have stated that the new 'floor' of the trailer is PT 1x6's.... been keeping an eye on it..., although i just put the floor on it in the past 2 months.
why?
rust is a perfectly acceptable colour......
I agree, but we aren't talking surface rust here, but continuing corrosion. I have to admit I found this out the hard way putting up a large section of board fence (oak boards on PT posts) using ungalvanized fasteners, which lasted only about 3 years- had to renail about 100 yards of fence, learned a bit. There was nothing left of most nails except their heads.
Most of the 'new' pressure-treatment chemicals (ever since the CCA treatment containing arsenic was banned and made unavailable for most folks, except 'exempt' stuff) are much-much-much more corrosive to metals than the CCA-treated lumber.
As in 6x-10x more corrosive.
Mostly based on the much higher copper content, which will rapidly corrode anything that is not very corrosion resistant. Stainless, triple-zinc or hot-dip galvanized, or 'approved' corrosion-resistant coatings only. That applies to the fasteners and any touching metal (brackets, flashing, whatever). No use of aluminum flashing, copper flashing only.
$$$$.
As in 6x-10x more corrosive.
Mostly based on the much higher copper content, which will rapidly corrode anything that is not very corrosion resistant. Stainless, triple-zinc or hot-dip galvanized, or 'approved' corrosion-resistant coatings only. That applies to the fasteners and any touching metal (brackets, flashing, whatever). No use of aluminum flashing, copper flashing only.
$$$$.
danski0224
Well-known member
It rusts. Quickly.
There has been plenty of discussion about ACQ lumber and proper fasteners over at Fine Homebuilding.
The consensus is that stainless steel fasteners and brackets must be used. Yes, there are many different types of stainless steel, but ACQ rated brackets and fasteners is what you need to look for.
The problem with coatings and plating is it chips or wears off during installation.
The buckets of ACQ rated colored fasteners have a warning that stainless steel should be used.
The problem with outdoor stuff built from ACQ lumber is the weather will always wet the wood, drawing out more chemicals; unless you live where it never rains or condensates.
ACQ rated, non-stainless hardware has been revised a few times in the last few years. This tells you that there are problems with the "solutions".
Double hot dipped to triple hot dipped, epoxy coatings, plasic coatings... etc.
ctgoodman
Well-known member
You will need to use galvanized for the most part. I built my son a swing set quite a few years ago and the screws where actually ceramic coated and designed for use in treated lumber.
danski0224
Well-known member
I wonder if there has been any damage or injury from not using the proper hardware with PT.Im not in a hurricane zone but If I were I might be wondering.I was in Lowes a couple of days ago and I had PT.2x4s in the cart.The Lowes guy was showing me regular wood screws and didn,t seem to notice the PT. stuff.I think they should be warning people about corrosion when they buy PT......Kirk
Most of the stores around here have multiple signs near the PT lumber section advising just that, to be sure to use the 'correct' fasteners/brackets when using PT lumber.
Also, the tag on the PT lumber says the same thing.
If you want advice, ask. Don't expect the check-out person to necessarily offer advice.