how should I attack the rust in this area

harrisonm said

I agree with George. All of these treatments are great except in tight areas like these where a skin wraps around a frame (as with hoods, decklids and doors). Any rust that is left in those tight bends (and it is unlikely that you will be able to get it all out) will come back. You are going to have to cut, fabricate and weld. I cut off the entire bottom 2" of my decklid years ago and fabricated all new parts and welded them in. Years later - no rust. Sorry to be a buzz kill, but that's how rust is. If you lived near me, I'd help you.

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Yep!
Soda blast media, depending on what's used, can itself and the residue be corrosive. If any residue creeps out of seems it can take paint with it. Rust-mort and Ospho which I have used both, and like, seem to work 100 times better when you can get the loose stuff off and actually get to the pitting. Not saying it won't help some, but there's just no way to get in between the panels to clean it up or insure that the Ospho gets down into the nooks and crannys. All you can do is clean it up the best that you can and hope for the best. Without getting the rust 100% gone the repair might last 6 months or 6 years you never can tell.