Man these rust threads never die...Weve discussed rust and how to remove it many ,many times...How about a few pics...Until then use the search button and use rust or Ospho for the key words.basicly stay away from the encapsulators,the only good way is to REMOVE the rust by using acid or media blasting or cutting it out and replacing with new metal... epoxy primer is best over bare metal...there are preferd brands of epoxies but you'll need to do a search on epoxy primers and do a little reading to get a fair and balanced opinion of what brand to use...
Be forewarned these two topics have enough info to keep you reading for a week...or two