Our baseboard radiators are less than a year old and accumulating rust. I know humidity is the cause (we're in the Northeast) and we have no leaks. We're not willing to trade off keeping windows shut on beautiful days and nights to run a dehumidifyer.

In that light, can we maintain/remove the rust with anything while preserving the paint?

 

Covers can be removed for restoration. Rusty baseboard heaters will need to be sanded with fine sandpaper to remove rust and to prepare surface for painting. Then, clean with degreaser cleaner to remove soil, and rinse and dry. Prime with a couple coats of rust inhibiting primer. There are spray primers, but brushing on primer assures that primer gets into pits and pores in surface. Then, paint with a couple coats of rust inhibiting enamel.

If rust is not severe and pitting of metal has not yet occurred, you may have success delaying restoration by removing rust with Scotchbrite pad, washing with degreaser cleaner, rinsing, and drying. Then, keep waxed with auto wax. While this may offer some protection on visible exterior surface of baseboard heater covers, rust will continue on the undersides where you can not see.