Rusty radiators is a common site in the UK , there are to main reasons the first being steam in the bathroom the second however can be avoided. Due to lack of care and the use of chemicals a large proportion of households at some point experience rust radiators , the simple introduction of a rust inhibitor can stop this happening.
the average price of a can of rust inhibitor is £15 and takes seconds to introduce into the heating system .It can either be sprayed into the system with a pressurised can or poured in ,there are may ways of doing both these methods .I’m going to post a you tube video on my Greg’s heating page to explain how to introduce chemical inhibitor .