Ospho penetrates the rust & seals it in as well as making a primer for topcoats I've used this product for over 30 years & have had nothing but positive results

encapsulators cap & insulate the rust it's still there & not getting any better
Eastwood introduced this product to coat frames & other thick metal parts that don't rust out as fast as sheetmetal.
They introduced it to save from sandblasting thus encapsulating the rust in
this is why the surface doesn't have to be perfect because you are just covering it up