PT wood in Aluminum Boats

Carl

Carl

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Staff member
A lot of the boats I am finding have had the floors and/or transoms replaced.
And in a good number of them, the people have used pressure treated lumber (PT).

Over on Tinboats.net, I have heard horror stories of transoms wrecked by PT, because the salts leached out, got trapped between the wood and the aluminum, and the salts and moisture corroded the aluminum until it was swiss cheese.

I have also heard from boat owner who swore the PT floor has been in the boat for 10 years with no corrosion on the inside hull and stringers.

My approach right now is that I'm not going near a boat with a transom replaced with PT, but maybe one with a PT floor is worth looking at before being wholesale disgarded as a choice.

So, whats y'all opinions/experience on this?
 
It would depend on the type of pressure treated lumber used. CCA lumber, the older stuff that was treated with an aresenic based material that went the way of the dodo in the early 2000's, should be fine with aluminum. The newer stuff the lumber companies swiched too is called ACQ and it will pretty much eat through fasteners/metals unless they are hot dipped galvanized, stainless, or copper (ACQ has a very high copper content). So you could always ask when the wood was replaced to help find if you might have a problem or not.
 
That could be, I used a lot of CCA with aluminum with no problems.
You could consider TREX, but it's heavy, and it doesn't have the structural strength of yellow pine.
 
That is re-assuring. The boat i am looking at had the deck put in back around 2000. So I am betting it is fine.
Its the new stuff that is a terror on metal, I remember watching a home renovation show about it right after it came out & they talked about how you had to use the new fasteners, etc...
 
That is re-assuring. The boat i am looking at had the deck put in back around 2000. So I am betting it is fine.
Its the new stuff that is a terror on metal, I remember watching a home renovation show about it right after it came out & they talked about how you had to use the new fasteners, etc...
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CCA is green, ACQ is much more yellow (but could be considered to have a greenish tinge). I would walk away from any boat with pressure treated in any form and run away from ACQ.
 
Just to throw another note onto Tod's post, I've seen that ACQ can also have a very bluish-green color to it, again thanks to the high amount of copper in it.
 
,One of the active ingredients in the CCA treatment is copper, copper is almost at the opposite end of the galvanic series from aluminum. Means in the presence of an electrolite- salt water or even mildly salty fresh water like a lot of the lakes in North Dakota, you are trying to make a battery. Bad situation for aluminum boats. Not as bad on floors,but real bad for transoms where the wood is flat against the aluminum, stays wet all year just eating away at the aluminum 24 hours a day.By the way if Im not mistaken the other two letters represent cyanide and arsenic! Sure does kill the spores that cause dryrot in wood. I know dryrot is a pain in the you know what to us boat guys, but if it didnt exsist the world would be 20 feet deep in dead trees! Use good marine plywood, fir is the most rot resistant, ocume un treated will rot away before your eyes, seal it real good with epoxy it will still be around for your grandchildren.
 
wood companies have switched over to items such as "nature's wood" that is enviro friendly..check with your lumber supplier and the company to verify the reaction to alum...the second issue is "crevice corrosion" the lack of oxygen will eventually corrode by the presence of moisture. when i replaced my transom in my lund i wire brushed the transom pocket down to bare alum and epoxied seal the alum, i hope i did the correct thing but i wanted to ensure that if the wood held moisture and was in direct contact with the alum the epoxy would protect the alum. do some research and crevice corrosion is a huge topic on alum boat.
 
Carl,

I had PT wood decks on my 1648 Lowe mod-v jon boat for 2 years. In the spring I was cleaning the boat and noticed that there was some pitting in the aluminum where the decks had rubbed. So, I cleaned and painted the affected areas and tore out all of the PT wood and replaced it with regular plywood. Lesson learned! Stay away from any aluminum boat with PT wood. I was lucky...
 
CCA stands for "Chromated Copper Arsenate" I believe it is a derivetive of copper.

All of the literature I have on it says STAY AWAY FROM CONTACT WITH ALUMINUM.

My experience is, it WILL EAT thru the aluminum. Although boats are usually fabricated from a more corrosion resistant alloy, it will still succumb very quickly.

And as stated, the older, ACQ treated wood was not nearly as corrosive.

Jon
 
The best bet to do the job once is to use aluminum sheet. I purchased the sheet .090 from the local hardware store. They cut to size for a couple extra bucks. Depending on size you can get it done for under $200.
 
Jon,

YOU are correct, I did transpose the two.

I work with the stuff most everyday, one would think I would remember...

About seven years ago, I covered a set of "new treated wood" step stringers with aluminum coil stock. About a year later, it looked as if someone had shot it with a scattergun. Full of holes, crusty and brittle. Soon it just fell apart. A little research revealed the corrosiveness of the product.

Doh!

Jon
 
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My best friend from college is looking at the hull today. I specifically asked him to look for corrosion where the wood meets the hull.
If I buy it, my first task may be to take the wood out, if it is in fact PT. Better safe than sorry, especially for the low cost of 1 sheet of plywood and some fasteners.
 
Ask any electrician what happens when you combine copper wire and Al in a wire nut or other type of connection......the movement of electrons makes a mess of the Al and causes electrical fires due to loose connections with arcing... The only way to prevent that is to have a physical/chemical barrier that isolates the Al from the Cu. Rich is 100% correct with what he said.
 

http://en.wikipedia.org/wiki/Wood_preservation
lkaline copper quaternary
Alkaline copper quaternary (ACQ) is a preservative made of copper, a fungicide, and a quaternary ammonium compound (quat), an insecticide which also augments the fungicidal treatment is a wood preservative that has come into wide use in the USA, Europe, Japan and Australia following restrictions on CCA. Its use is governed by national and international standards, which determine the volume of preservative uptake required for a specific timber end use.
Since it contains high levels of copper, ACQ-treated timber is five times more corrosive to common steel. It is necessary to use double-galvanized or stainless steel fasteners in ACQ timber. Use of fasteners meeting or exceeding requirements for ASTM A 153 Class D meet the added requirements for fastener durability. The U.S. began mandating the use of non-arsenic containing wood preservatives for virtually all residential use timber in 2004.
 
http://en.wikipedia.org/wiki/Wood_preservation
lkaline copper quaternary
Alkaline copper quaternary (ACQ) is a preservative made of copper, a fungicide, and a quaternary ammonium compound (quat), an insecticide which also augments the fungicidal treatment is a wood preservative that has come into wide use in the USA, Europe, Japan and Australia following restrictions on CCA. Its use is governed by national and international standards, which determine the volume of preservative uptake required for a specific timber end use.
Since it contains high levels of copper, ACQ-treated timber is five times more corrosive to common steel. It is necessary to use double-galvanized or stainless steel fasteners in ACQ timber. Use of fasteners meeting or exceeding requirements for ASTM A 153 Class D meet the added requirements for fastener durability. The U.S. began mandating the use of non-arsenic containing wood preservatives for virtually all residential use timber in 2004.
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Damn enviro-wackos - who has ever heard of Arsenic being toxic? It isn't like anyone ever died standing on thier deck in bare feet.
 
Tod,

It sure it kills the foot fungus......best darn treatment ever...

One arsenic issue was the change in allowed amounts in drinking water a few years ago. Some towns in Utah had to drill new wells as the older wells supplied water with arsenic concentrations above the new limits...
 
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