Dan ,
CB is right . all you need is to go to Home depo and get you some tile cleaner .
its only about 3-5% muric .
i used to use it all the time for cleaning up after a Tile job . just soak you plate in it and it will take the crome plating right off .
as a note , it will also take the crome off od sink drain caps
, dont ask me how i know LOL