Unpacking my tail kit parts from the move (boxed ~5 months) I found surface corrosion in exactly those spots, much of which were no longer covered by the blue film. Pictures below. Its nothing that a bit of scotchbrite wont dress out, but I still found it quite interesting. I think once my wing kit comes Im going to clean as much of that stuff off as possible.
Here is a picture of my rudder counter balance skin, notice the '03' in '032'. This part had been fully prepped (except priming/alodine) and the blue film was removed.

Here is a better shot of it up close and personal. The first number you see is the '3' followed by the '2', which is not nearly as bad.

Pretty wild 'eh?
-- John