A few years ago I questioned Laminators about mounting alumilite and luster board into slots made in the new treated lumber made with copper sulfate. They said no problem only to find out several signs had eroded severely. Since then I edge trim all my blanks that will be touching treated lumber or I tell my customers , if they are mounting it using there own lumber to insulate the edge with electrical tape. It has been a hit or miss thing. Some old signs never perhaps had a good contact, and were fine, yet some destroyed.