Hi Featherock,
According to JohnB, Sunline got a bad batch of vents. Sorry to hear you've been bitten by the same problem. The vent frames are galvanized steel. I would not mess with trying to extend their life. Vents are a pain to remove and easy to bend as they are being pried up. IMHO you're far better to ditch the defective ones and maybe even put in a new Maxxair fan.
See my post, which also references JohnB's original post about replacing his defective vents with lots of pictures and a second post by JohnB for installing a Maxxair fan overtop one of the vents. These posts will give you all the info you need--use butyl putty tape and Dicor Self leveling caulk, not Eternabond. Several members have done vent replacements so ask away with any other questions.
http://www.sunlineclub.com/forums/f6...hlight=maxxair
Don't forget to put some boards and/or 1/2" plywood on the roof to make a work area.
Henry
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