Chemtec, purchased from my local yacht chandler,is my new favourite chemical.It's formulated to return old stainless steel to near new, shiny brightness. Just dunk it in,leave for a few minutes and then brush with an old tooth brush
Rinse with fresh water and presto! Peugeot seat binder bolt all shiny and new.
note: you don't need to pour the used liquid away. Just return it to the bottle and use it again (and again).Then, when it's reached the end of it's life,take it to your local waste transfer station for safe disposal.