I've been using a product called FLUID FILM for the frame and other rust prone spots. It doesn't affect paint. It displaces water and can be sprayed or brushed on. Label on the can says non toxic, silicone and teflon free, non evaporating, non drying contains wool wax and other rust inhibiting ingredients. Apply over damp or dry surfaces.
I don't know whether you can find it in the U.S. but here's their website www.nlsproducts.ca
pete
I don't know whether you can find it in the U.S. but here's their website www.nlsproducts.ca
pete