Getting rid of rust completely?

Crabman

There's a product called "WaxOyl" which supposedly kills old rust and protects against new, but I've not found any experiences of whether it works properly.

I have a corroded outer sill (about 10cm long) which will be welded up soon.

Pssst

Just bear in mind that rust or oxidisation is simply a chemical reaction which requires air and moisture. If you have existing rust,you must get rid of it completely and then insulate the metal from the iar/moisture by applying a surface coating. If you dont get rid of the rust completely,the process just continues under the new coating and eventually shows through.