I use Corrosion X and, since I am in Florida, I have it applied every two
years. We took the covering off the wings prior to recover and there was a
slight, sort of oily, film on all the metal components and it did not affect
the old wing cover (grade A cotton). It is applied by poking spray wands into
every conceivable opening and also by creating openings in areas that you can't
normally get to. A #40 size drill or so is used to create a small hole in some
areas of skin and the product is sprayed in under high air pressure. The holes
are usually on the bottom side and hardly noticable unless you know they are
there, even in the side of the vertical fins (can't really call them "rudders")
Bart