Help me touch up this radiator!

[Circumferences]

I've never painted a radiator before. The internet tells me to sand off the existing paint, spray a layer of primer on the metal, then spray a layer of white enamel radiator paint over that.

Before I mess it up, what am I missing, what could go wrong?

If anyone could help!

I had a radiator with rust spots on the bottom edge. Hard to see except from certain angles.

I just sanded down the area and then painted straight on with radiator paint.

The area is not really that visible, so didn't matter that the two whites don't match - you can only see if you get down on your knees and squint closely.

i think your biggest problem is if you only paint a part of the radiator the colours won't match, so if it is a large patch in a highly visible area you are probably going to end up painting the entire radiator again.

You don't need to sand all existing paint off if it is mostly sound - if you're going to go to that length of faff you might as well just buy a new radiator.

On mine I just removed loose/flaking paint, sanded all rusty spots back to bare metal, primed only the bare metal areas, and sanded lightly all over to key the new paint. Washed with sugar soap, rinsed and dried, then brushed with 2 coats of Dulux Quick Dry satinwood paint (water based paint, which the can says is fine for metal).

The radiator needs to be cold while painting and for several hours afterward when drying. Still looks good after almost 5 years though, and none of it has flaked off.

If you don't want to paint the whole radiator, you might be able to get away with doing a "rung" or two (assuming that's a ladder style towel radiator in your picture). If you normally have towels draped over it you're probably not going to notice the difference in paint colour.