I found this article online as far as pressure treated lumber goes. Your boat looks fantastic and I would hate for all that work to be ruined as well as be more expensive than need be EXCELLENT WORK!
Your Place: Pressure-treated wood and aluminum don't mix
By Al Heavens
Inquirer Real Estate Columnist
Question: We have a house at the Shore, with a second-story deck supported by pressure-treated wood. It was built after they banned the old arsenic pressure-treated wood. We had the wood capped with aluminum.
After 18 months, the chemicals in the wood seemed to eat through the aluminum, which had to be replaced. The builder put Tyvek between the wood and the aluminum capping, but the same thing happened. Is there any way to avoid this problem?
Answer: It's pretty obvious that your builder missed something in the directions for the new pressure-treated lumber. It's this: Avoid aluminum flashings altogether. Aluminum corrodes quickly in the presence of high copper concentrations, which is how this generation of lumber can perform without the arsenic with which the old wood had been impregnated.
I have done a lot of reading about Tyvek, and nowhere does it say that it should be used to shield aluminum from corrosive high concentrations of copper. Instead, galvanized or copper flashings should be used.
You ask about PVC flashing, and I think the same rules apply. No.
Tests show that the concentrations of copper in alkaline copper quat (ACQ types B and D) and copper azole (CBA-A, CA-B) are five times more corrosive to common steel than the old CCA (chromated copper arsenate) used in the old pressure-treated lumber.
That means joist hangers and fasteners need to be stainless steel, copper, or a heavier grade of galvanized fastener.
