I have recently had a new central heating system installed and i have now taken one of the raditors off to decorate the room it is in. I made the suggestion to my girlfriend that we should use this opportunity to paint the radiator as it has not been painted before, even though it will just be painted white (the colour it is already). She laughed at me saying we didnt need to do this. I thought painting the radiator would protect it more. who is right?
Im not sure how painting a radiator will protect it but i would paint it. If you have just decorated a room you might as well finish it properly even if the rad is new.
Radiators usually only have one spray coat of paint that is usually sufficient for its life but there is no reason why you shouldn't paint it again especially if you don't like the colour. Check that the paint is sufficiently heat resistant of at least 120C. You can get brushes to get behind the fins to do a good job.
You can buy a special radiator paint which is more heat resistant than ordinary gloss paint. Not sure if there is a choice of colours though.White is the only colour I have used.
In a painted room I generally paint radiators the same colour as the walls. It minimises their attempt to say 'look at me, I'm a radiator'. I've painted rads with Dulux emulsion many times with no problems. At a trivial level, matt surfaces radiate more heat than shiny, but I don't claim that as a good reason for doing it.
Most rads, unless they have been bashed and buffeted, usually only need a good clean. Though at customer's request, I have often painted the rads in same colour emulsion as walls so they 'blend in'. However, when doing rental properties, I usually recommend rad paint to landlords. I'm not paying for it so why should I worry.