Search for rust, and you will find other posts on the board in the past month or so regarding rust removers. Keep in mind that most rust removers are an acid, so use protection and read the directions carefully.
As far as the loose rail, you don't say how it's connected. If it is bolted to imbedded bolts, tighten the nuts. If the rail was cast into the concrete and now it is loose, which is where I will suspect the rust is coming from, then you have a rail that is about to come out altogether from rusting out.
Without a lot more information, can't say how to fix it.
Post back with more info, someone should be happy to help...