One of the issues of using oil based paints in hot surfaces is that they tend to be less stable. White paint will yellow quicker and some will crack / fail. So choosing a specialised paint rather than a common gloss / eggshell is a good idea.
All loose paint needs to be removed before applying a new coat and a ‘key’ is required in order to allow the new paint to cling onto the surface. But is there a natural paint option?
Thankfully Yes. Auro have developed a thermally stable radiator paint that is water based, natural and easy to use. It can be tinted to give a more stable colour than white if needed, but the actual paint is really good quality and will last years.