I think if you get rid of the rust and paint it right, you should be fine if you wanted to seal it. Granted, the only seam sealer I have used is on marine applications. I use 3M brand because it takes paint well. A word of caution, though. I have found in my applications that some seam sealers are solvent based, and do not last long. Make sure you find one that isn’t solvent based, and they last much longer. I have some 3M sealer around the wheelhouse of my boat, that I put there several years ago that has held up nicely. When I renovated the boat I wire wheeled the rust, and applied 2 coats of primer and pant before sealing it...good luck!