Copper is green. The new treatment is far worse than the old treatment, they increased the copper content and removed the arsenic. Anyway it is the copper that is used in the treatment that causes the corrosion. Pontoon boat manufacturers use the old style treatment (CCA old as opposed to ACQ new) on their boats and so does some tin boat manufacturers, If it is insulated from the aluminum it will be fine. I have a Sylvan and the factory used CCA treated plywood in the transom of my boat, they did not insulate the wood from the metal and you can look at my re-build here. https://www.tinboats.net/forum/viewtopic.php?f=3&t=23064
The wood is fine but the metal is not. I would use either marine grade ply or exterior ply and coat it with epoxy, if you use polyester resin you better use glass too because the polyester will just flake off, been there done that.
The wood is fine but the metal is not. I would use either marine grade ply or exterior ply and coat it with epoxy, if you use polyester resin you better use glass too because the polyester will just flake off, been there done that.