Por15, Eastwood rust encapsulator something else?

We had the frame on a friend's Chevelle powder coated years ago. No way in HECK would I do it again. There' ZERO way to get inside at every nook and crannie. No way. Now, it's got rust coming from inside the frame and getting under the powder coat on the outside and flaking it off. I tried to tell him.
The good thing about these power wagon frames is they're not boxed in, so you can get every nook and crannie...