Bad for an alum. jon to sit on carpeted, treated 2X4s????

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G Lap

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I recently rebuilt my old trailer for a new jon boat. I replaced all the rusted fasteners, replaced the old rusted springs, replaced the jack & winch, repainted it and also replaced the boards that the boat sits on. Not thinking that it might damage the aluminum boat, I used treated 2X4s that I covered in carpet for the boat to sit on.

Will the treated 2X4s cause corrosion to the bottom of the aluminum boat through the carpet? Will the layer of carpet protect the bottom of the boat from the treated lumber? I dont want to damage the boat, as I just bought it and it will be sitting on these boards for a long time. Should I replace these boards with common untreated 2X4 studs?

What type of wood are you guys using, for your boats to sit on? Thanks for the help.
 
I had carpeted treated on a trailer purchased last year. Below the 2x4 where it rested on the I beam was rusted away pretty bad. I think you could be okay in regards to the boat as I'd be more worried about contact points on the trailer considering drainage. Prob best to just keep an eye on it, look for the start of fine pitting in the aluminum.
 
That is actually a very good question. I am not sure what is used these days, but CC-Arsenate and other chemicals used in PT do not have ill effects on aluminum raps or SS screws in the decking world. The aluminum there is much thinner and you would expect if it was an issue, you'd see it there first. Nothing comes to mind.

I've always used PT lumber for my guide and bunk replacement then wrapped it in carpet. On my bunks, I put strips of UHMW (either kits or just cutting strips from full UHMW sheets) so the aluminum never really sits directly on the carpet or wood... but again, never heard of an issue.

My buddy had his new jet boat in the lower section of his 150 year olf bank-barn. It was out of the elements on a hard packed dirt floor where his tractors use to sit and out of the way... The main floor of the barn had stored items like bulk lime on pallets for the fields the coming season. That spring when he opened the lower doors, he noted the aluminum deck had pock-marked errosion. There was white powder on it and he surmised that broken bags of lime filtered through the floor each time the tractors came in and out of the main floor. Damage was significant enough to replace the whole deck. If it wasn't the lime, he's not sure what else could have done that?

I'm no chemist, but I've seen what lime does to breakdown carbon based items like dead livestock...
 
Darkside,

What are the aluminum wraps you mentioned, used in decking? Also, what is UHMW? Is it a type of plastic or polymer? Where can you find it? Thanks.
 
I'd change them out 2x4's don't cost much. The carpet will stay wet and help the copper used to treat the wood leach out.
 
Not sure about the wraps mentioned, but...ultra high molecular weight (UHMW) polyethylene. Think cutting boards like the butcher uses.
 
The copper in the treated lumber is bad, and the carpet actually does make it worse as it retains water.

Even without the treated lumber (ie. copper), the carpet causes problems of it's own, as it will retain water. The problem there is that the aluminum (in trying to form aluminum oxide), will start to pull oxygen molecules out of the water, causing the remaining water to become more acidic. This becomes a much greater issue in saltwater rigs, as you suddenly throw high quantities of salt into the mix, but still potentially can be an issue in freshwater, to some extent. However, with that, I can't say I haven't used carpet on bunks in the past, nor can I say that I won't in the future (we are talking freshwater rigs only), but it isn't necessarily good practice.

The best solution is some sort of plastic (HDPE, UHMW, etc.) with drainage grooves routed in it.
 
You're absolutely right about the issue of carpet holding moisture and causing corrosion. If the bottom of the boat is properly painted with anti-fouling paint, it's not as much of an issue. I have carpeted bunks, but the bottom of my boat is painted, and I haven't had any problems. However, people have brought bare aluminum boats to my shop, with leaks in them, that have sat on carpeted bunks, and the leaks and corrosion are almost ALWAYS in the area of the bunks.

But after thinking about this, I may eventually change my bunks to the UHMW skid type, instead of carpet.
 
Hmmmm . . . . maybe after 12 years I should look at my bare aluminum sitting on carpet.
 
PSG-1 said:
You're absolutely right about the issue of carpet holding moisture and causing corrosion. If the bottom of the boat is properly painted with anti-fouling paint, it's not as much of an issue. I have carpeted bunks, but the bottom of my boat is painted, and I haven't had any problems. However, people have brought bare aluminum boats to my shop, with leaks in them, that have sat on carpeted bunks, and the leaks and corrosion are almost ALWAYS in the area of the bunks.

But after thinking about this, I may eventually change my bunks to the UHMW skid type, instead of carpet.

I'll note, for the sake of discussion, that one needs to be careful with bottom paint (the true anti-fouling sort), as much of it, too, contains copper.

That being said, I can't see putting bottom paint on a trailer maiden, anyway. Not going to hurt anything, but not really a necessary cost.
 
After seeing these post I went & looked at my tin that sits on carpet for many years & no problem at all with any corrosion.My tin bottom has no paint on it.
 
:twisted: Bunk caps should solve any corrosion problem. I just put a pair on my trailer this year. I think they go for $40 at BPS/Cabelas. The self centering feature also makes it a breeze to load up.
 

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I'll note, for the sake of discussion, that one needs to be careful with bottom paint (the true anti-fouling sort), as much of it, too, contains copper.

That being said, I can't see putting bottom paint on a trailer maiden, anyway. Not going to hurt anything, but not really a necessary cost.


Right. It should be noted that there is one specific type of anti-fouling paint, formulated for aluminum.

Copper Thiocyanate is the ONLY type of anti-fouling paint you should EVER apply to an aluminum boat.

NEVER, and I do mean NEVER apply 'cuprous oxide' based anti-fouling paint Cuprous oxide is meant for use on wood or fiberglass, NOT aluminum. If you apply this type of paint, and it stays in salt water, your hull will look like the hull of my Aluma-jet when I bought it several years ago....the bottom will be pitted, if not outright fully corroded.

Also, to insure proper adhesion of any type of paint to bare aluminum, you should always etch with phosphoric acid, throughly rinse, and then apply a coat of zinc chromate primer. If you don't use the zinc chromate, chances are the coating will begin to flake.
 

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