If you are talking about the exterior frame, suggest you to Wrap them up with metal sheet, once and for ever (may be I shouldn't say for ever, should say for a long time) Painting lasts only a few years.
I have a lot of experience with painting. Please call me at 780-604-6133. My name is Man. I speak Cantonese/Mandarin. & t+ E M i! d+ M. K/ ~& V" F) _( Q
Look forward to hearing from you soon. Thank you