Treated plywood deck and alum boats-Don't do it!

[peter]

I found out the hard way not to use the newer treated plywood in an aluminum boat.

In 2004 the EPA made the treated plywood companies take out the arsenic and they put more copper in the wood. Well...copper and aluminum are dissimilar metals on the galvanic scale and once you add water it creates an electrical current, like like if your carpet and deck stays wet or a period of time, the copper will interact with the aluminum and eat holes in your hull and completely trash your boat. It appears to have dripped and/or pieces have fallen down to the inside surface of the hull.

Electrolysis or galvanic corrosion whatever you want to call it, is bad news, and can cause severe depression upon discovery. It even soaked/wicked upward through the carpet and munched away at the bottom surface of my aluminum live well that sits on top of the carpet.

If you think you may have this newer treated plywood in your boat I would think it is best to keep the deck as dry as possible (water or a solution is necessary for this take place-my understanding) or better yet replace the deck. Leaving a boat with such a deck uncovered out in the rain like we have been having around here lately I would think would most definitely be a problem.

You can google something like "treated plywood aluminum corrosion" or try some different search terms. There is quite a bit online about this.

You will probably come across some instances of folks with fairly new boats (anything 2000 and above is new to me) that reported holes and bubbles in their transoms. The plywood was eating up the transomes from the inside out. Some manufacturers apparently were not aware of this and they used the copper laced treated plywood in the transoms. Some of the stories are pretty bad as some manufacturers where not acknowledging the problem and being very quiet about it.

There are even some stories of treated plywood bunks being a problem which makes sense to me having seen the bottom of my live-wells. Now I would not think the bunks would be as big of a problem as the deck because it does not seem like the bunks would have the opportunity to stay wet as long as the deck. Marine carpet has a rubber backing that should prevent the copper from wicking upward but the backing on my carpet had deteriorated allowing the copper to interact with the bottom surface of my aluminum live-well (what else could explain it). Also bunk carpet gets torn up pretty quickly and exposes the wood. I am replacing the bunks on my old trailer which is under my new (used) boat sometime soon.

Building contractors probably know about this problem but it does not seem to be as will known around here as it is up North as it relates to boats. If you go to a plywood or lumber association website there are instructions not go use treated plywood near aluminum siding on houses. They also instruct to use coated fasteners as copper will eat up traditional fasteners.

-- The one question I have, if there are any scientists on here is:

Does ice have the same effect as water on this process?

For example if a boat were sitting outside in the winter in rain and snow and the carpet/deck had ice on it would that be the same as water?

One guide up north had a good take on this. He said "I ride with nothing but glass under my bottom" Replace the word bottom with something that rhymes with "glass".

[olgreenboat]

Try using an anode to kill this reaction Pete. You usually have to have some kind of power to crate electrolysis . Are you parking your boat under a power line or something? Do you use you're boat as a ground supply . Running the ground wire to the boat and grounding everything to the boat. Just trowing out some ideas..

[bob46]

Peter Im far from a scientist but Im in the remodeling buisness, and this has been a problem in the past with aluminum and treated lumber. Generally speaking if you are going to use treated around aluminum must put down a barrier over the aluminum so the aluminum will not get eaten by the chemicals in the lumber. If i was going to do a boat over I would get a piece of aluminum for my deck expensive yes but maintence free. My dream boat will have aluminum decks no lumber, and coat the decks with that spray they use in pick up bed liners. Though I would chime in and tell you what I know.
Bob

[markmac60]

Peter, you have a PM.

[coombro]

After replacing my floor boards and deck numerous times I've had my boat 20+ years. I decided enough was enough. I coated my wood with fiberglass resin. Keeps moisture out and has lasted me for the past 7 yrs. Feel like its just as good as the day I coated it.

[peter]

I hear ya. Alum deck would be great. Wood is heavy too.

I've seen some sprays in a Crestliner compartment that looked real nice. There are probably some options on the spray now.

[peter]

Thanks. I'll look into that when I have to replace the deck in my newboat. One of the things I liked about the boat I bought is that it has the original deck and carpet and was built way before 2004 so I knew the deck did not have the bad stuff in it.

[HURRICANEBOB]

Marine ply, 1088 and 6566 grade, are not chemically treated and will not cause corrosion in an Alu. hull. They are simply a high grade hardwood ply, with no voids, more laminations per sheet and a glue that is water rated.

What is Marine-grade plywood?
Marine-grade plywood is a specially designed panel made entirely of Douglas-fir or Western Larch. The grade of all plies of veneer is B or better, which means it may have knots, but no knotholes. The panels are sanded on both faces, and are also available with Medium Density Overlay (MDO) or High Density Overlay (HDO) faces. The maximum core-gap size permitted is 1/8 inch. Its exposure durability rating is EXTERIOR and the glue used is a fully waterproof structural adhesive. It is considered a “premium” panel grade for use in situations where these characteristics are required, i.e., for boat hulls and other marine applications where bending is involved.

Costs:
Lowe's: 4ft x 8ft x 1/2in Fir CDX Treated Plywood $24.95
www.almquistlumber.com: 12MM HYDROTEK MARINE MERANTI 9 PLY $71.55 or 1/2" 4X8 AB MARINE PLYWOOD $64.45

Or, what about composite decking?
Pontoon Stuff: 4'x8'x3/4" sheets Coosa Composite Pontoon Decking US $225.00

[ryan_ekubass]

Try using an anode to kill this reaction Pete. You usually have to have some kind of power to crate electrolysis . Are you parking your boat under a power line or something? Do you use you're boat as a ground supply . Running the ground wire to the boat and grounding everything to the boat. Just trowing out some ideas..

is there a ground wire that runs from the motor to ground it out... I know on atv motors adn such there is a ground wire i dunno if this would have an affect.

[hairball]

I don't mean to hijack this thread, just wanted to make
everyone aware that there's a product available called Nautolex that is all vinyl and can be used instead of marine carpeting. It glues on just like carpet and is very easy to work with. Cost is comparable to carpet and you don't have to worry about hooks getting caught in it. It has a textured finish and is very easy to keep clean - just hose it off! I found mine online - don't remember the name of the outfit but they were in Florida and there's a dealer in the Carolinas somewhere. It's also available at The Wooden Boat Shop in Cincinnati. I installed it over 3/4" marine ply 3 years ago in my '84 Tracker and absolutely love it!

[peter]

Thanks. I have seen this stuff in some new boats and liked it a lot. Seems like it would also keep your plywood deck from getting wet if you wrap it around the edges onto the bottom. I have seen installations with the vinyl installed over the screws and some with the screws installed through the vinyl. Lund had some nice screws through the vinyl that looked good and did not stick out too much. Bass Pro has some of this stuff on a flat bottom boat out front in Clarksville, IN. or maybe that was the spray Rino linner or both, can't remember.

The advantage of screwing through the vinyl is if you have to remove your deck to tighten some rivets or something you can just unscrew and screw it back with out ripping up the vinyl or carpet. It's a good idea to look at the top side of your hull every year or so if you can, in case there is something going on down there.

[coombro]

Marine ply, 1088 and 6566 grade, are not chemically treated and will not cause corrosion in an Alu. hull. They are simply a high grade hardwood ply, with no voids, more laminations per sheet and a glue that is water rated.

What is Marine-grade plywood?
Marine-grade plywood is a specially designed panel made entirely of Douglas-fir or Western Larch. The grade of all plies of veneer is B or better, which means it may have knots, but no knotholes. The panels are sanded on both faces, and are also available with Medium Density Overlay (MDO) or High Density Overlay (HDO) faces. The maximum core-gap size permitted is 1/8 inch. Its exposure durability rating is EXTERIOR and the glue used is a fully waterproof structural adhesive. It is considered a “premium” panel grade for use in situations where these characteristics are required, i.e., for boat hulls and other marine applications where bending is involved.

Costs:
Lowe's: 4ft x 8ft x 1/2in Fir CDX Treated Plywood $24.95
www.almquistlumber.com: 12MM HYDROTEK MARINE MERANTI 9 PLY $71.55 or 1/2" 4X8 AB MARINE PLYWOOD $64.45

Or, what about composite decking?
Pontoon Stuff: 4'x8'x3/4" sheets Coosa Composite Pontoon Decking US $225.00

I started to go that route as weight was a factor for me and I was told that once you cut into it you had to treat the edges? Thats why I went with the fiberglass route.