While I am by no means in love with metal baseboard heat covers, they are after all rather ugly, changing out heating systems is very costly. Painting baseboard heat covers can spruce them up though, and help them to blend in with your design scheme. They were not in particularly bad condition in my house when we bought it, a few specks of rust here & there, some scratches and splotches, but they certainly needed a makeover. I thought I would share the refinishing process with you, in case you also have metal baseboard heating covers that need to be repainted.
Painting Baseboard Heat Covers
Prepping the Surface for Painting
Step one is to completely disassemble the covers. If there are a lot of pieces you may wish to label each piece on a non visible while assembled spot, so you will know where they go when it is time to but everything back together.
Sand the pieces lightly with 100 grit sandpaper. No need to be fussy in the sanding, you are just trying to sand off and rust, and give the finish a little tooth. If you have more rust, you may want to use a heavier grit in those areas, to get it off.
If the covers are really grungy you may want to wash them down before sanding, but this shouldn't be necessary in most cases.
Painting the Covers
I use a semi-gloss oil paint without primer. The paint is thinned down a little with paint thinner to glide on smoothly (10-20% thinner). This is the same technique we have used on other baseboard heat covers in the house, and the finish has withstood the test of time without issue. Make sure to use a good oil or all purpose paint brush.
To get a nice consistent finish, two coats of paint should be done. Allow ample time between coats, to allow for drying. After second coat make sure to let the pieces dry well before reassembly. If they are still tacky at all, you risk ruining the nice paint finish you have worked for.