Is There A Rust Preventative Coating?

I'm starting to work on the body of my 71 Duster, cloned from a 74 Dart Sport. I have a pair of 72 Duster doors. They have surface rust on the insides, at the bottom. What can be applied in there to put the rust to "sleep"?
I'm thinking it could be used in several places.

The Eastwood rust encapsulator I have been using seems to stop it from progressing.
Now when the rest of the car returns to dust there will be some nice seams laying in it.:D