Is it OK for treated lumber to touch my galvanized trailer? My plan is to bolt treated 2X4's (lying flat, with galv. hardware) to the top of my trailer frame, then mount bunk sliks on top of the treated lumber. I'm getting conflicting opinions on whether or not the treated lumber will cause the galv. trailer to rust. What if I put some sort of barrier between the trailer and treated 2X4's? My other options seem to be:

1) Cedar 2X4's. Probably not strong enough though.

2) Regular 2X4 pine. I don't know how long they would last though.

Whatever I use needs to span 42.5"(the span between the 2 trailer frame members.

Thanks.

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I've viewed the question, and cannot provide you with a definitive answer.

 

They used to use copper in the solution for pressure treating lumber which could cause a reaction with the zinc which plates the fasteners.  Zinc is used in sacrificial anodes to prevent electrolysis and galvanic action from destroying critical metal parts of a boat such as fastenings, propellers, propeller shafts etc.

 

A few years ago, if I'm not mistaken, they stopped using solutions with copper, and I have no idea if what they now use will react with zinc.

 

It may not be a problem either way, since the trailer does not remain in the water for any length of time.

 

This does not definitively answer your question, but it's the best I can do.

Thanks Tom. What I found online mostly states that fasteners need to be "hot dipped galvanized". BUT how do I know if my trailer is hot dipped galvanized? If I use standard pine, any idea how long the bunks would last? I only launch my boat about once per week anyway. And when it sits outside, the bunks won't get wet.

Xpress & Alweld both use treated lumber on their trailers with no problems.

Arch Chemicals who owns the treatment process used for making pressure treating lumber changed the chemicals used in that process making it more compatable with most metals.

Xpress & Alweld both use treated lumber on their trailers with no problems.

Arch Chemicals who owns the treatment process used for making pressure treating lumber changed the chemicals used in that process making it more compatable with most metals.

Thanks. My trailer is a Karavan. Maybe I will call them and see what they say.

I'd stay away from pine, unless it's the southern yellow/long leaf pine.  Too soft and often with sapwood (the wood near the surface of a log) which is not very durable.

 

I'd pay the extra for fir.  It should last for years.

I'd stay away from pine, unless it's the southern yellow/long leaf pine.  Too soft and often with sapwood (the wood near the surface of a log) which is not very durable.

 

I'd pay the extra for fir.  It should last for years.

Thanks again. I never thought of fir.

If you can find some long leaf, yellow, southern pine go for it.  It is very resistant to rot.  Most of the wood shrimp boats in the gulf and southern states were built of yellow pine.

Am I right in thinking cedar is not strong enough for bunks? I could use 2X4 or 2X6's. They need to span 42" lying flat.

I don't know about cedar since I have no experience working with it.  Cedar is used in boatbuilding.  There is red cedar which is usually used for closets and trunks for storing clothes.  There is white cedar which is used in rowboats, canoes, skiffs, etc.

 

I really have no idea if it is suitable for bunks.

Used treated 2x4s for years on my galvanized trailer and never had a problem.

Hot-dip galvanized hardware will work well in contact with treated lumber---the deck people are recommending it for treated wood decks.  There will not be any problem with using the treated material with anything that is galvanized.

 

Another place you can get info on this is the American Galvanizers Association website.

Thanks. I'm not going to use treated lumber anymore. I'm going to use fir, so I don't have to worry about trailer rusting.