Rusty Radiator

buy a tin of nitromose, then paint onto radiator, leave for an hour untill the paint has gone soft, then using a thin scraper, scrape off paint. use gloves at all time and goggles nitromose is an irritant and avoid getting into eyes at all times please read instructions before using have a lovely day!

Check there are leaks around the seams or valves of the radiator.
Radiators need to be thoroughly sanded down or treated with the paint remover as left over paint will probably bubble If just overpainted with enamel paint.
Use a radiator paint primer and ensure the coating is not stepped or overloaded with too much primer.
Best finish for a radiator is to use radiator spray canisters available from most DIY Stores such as Wickes, and B&Q.Soray in a smooth regular action 6-8 inches away from the radiator.Avoid hand brushing as this creates unsightly tramlines on the radiator, and irregular thickness of paint on the radiators angled metal structure.

Blue based coat primer about 4 coats then the colour of choice and u should be good there on

Sticky Oily paint would be the best paint to use. And at least 2 to 3 coats.

Hiya
You can buy a Hammerite that are for radiators, or jenolite which you can buy on amazon.

The radiator needs replacing. Or needs completely scraping back to bone. All paint and enamel needs to come off. It then needs to be sanded, then sanded with wire wool and completely started again.
Enamel coating spray
Prime
Undercoat
Metal paint

But I would fully recommend a replacement radiator as this would out price the customer

Before painting, everything must be thoroughly cleaned and rust removed. HAMMERITE RADIATOR ENAMEL METAL PAINT I order two coats

i’ve personally used zinsser cover stain to go over rust and it’s covered perfectly so i would recommend trying that

You should use just radiator paint or you can you use also any oil based paint. If you don't want rust anymore paint with zinsser bin paint first Red can.

If you're dealing with rust on a radiator, you can use Hammerite Direct to Rust paint. Treat the rust first with a rust converter or remover, then apply a suitable primer before painting. This should help address the rust issue effectively.