waterproofing plywood

When I was a truck driver I was told on a slow day by "the boss" to coat the 40' trailer's wood deck with 30W engine lube oil. I thought it would just help it rot but the truck bed was recoated several times over about ten years and remained in good shape. The decking may have even been Hemlock.

 

You might want to consider an oil finish which is not waterproof. Tung oil mixed with citrus solvent (nicer than turpentine) would be my choice. This sort of stuff has been preserving traditional boats left out in the sun for many decades. See for example: http://www.realmilkpaint.com/tips-techniques/how-to-finish-decks-and-porches/

 

most petroleum products, such as motor oil or paraffin wax, kill and repel wood eating organisms so it preserves the wood. the problem is neither will allow most paints to bond to the wood, so it would only work if you intend to the leave the wood in an oiled state. Which would likely be okay for a trailer deck, though it would make it somewhat slippery, and you would tend to pick up the oil on your shoes, hands, etc. on hot days.

 

Oiled surfaces don't have much UV protection, regardless of the oil employed. There are some bugs that are attracted to petroleum products, others that live in and on it. An old school trick was to use used motor oil, to keep things from rotting and it works to a degree, but has other disadvantages, such liking the color of black and very dark brown as the only finish coats possible.

 

Sprit,
Interesting about the citrus solvent. I frequently use turpentine as it's reported to be a natural fungiside. Does citrus solvent have that property as well?

Where would one buy citrus solvent?

 

Greetings,

Still think one coat of epoxy, three at edges, with coat of UV paint would perform well as ext. ply can stand some wetness as long as its able to dry out, the epoxy would keep majority moisture out. Excessive vibration or abrasion would cause some concern by wearing away to much epoxy but even then it should be able to go a decade.

This has me wondering if there is any ply that would be able to withstand constant immersion in water with just antifouling or paint system?

Peace.

 

Keeping the "majority of moisture out" will also permit some to remain, which will lead to issues. The whole point of epoxy is to actually seal the wood. If you want to coat it with something that seals the "majority out", then a good quality paint is a lot cheaper and easier to apply too.