I'm repairing a rusted out area of the wheel arch with bondo hair and backer. The area is not huge, but the edges had seam sealer where the panel edges meet, which I had to remove so I can deal with rust. Removing the seam sealer revealed rust and also shiny metal. It is clear that where there is rust, the seam sealer no longer had good adhesion. The seam sealer was applied in a thick bead along the panel edges, but spread thin about 2 inches from the edge inside of the panel. I'm doing my best to remove rust from all visible areas to be repaired, but I'm concerned that there may be other areas within the panel that cannot be seen nor reached--meaning I will not be able to sanding or observe for issues.

I'm wondering what to spray between the panels that can deal with any potential rust within and prevent the formation of rust in the future.

I've sent an email to Eastwood waiting to hear back.

Also wondering if Rustoleum Rusty Metal Primer or what other products might work if sprayed within.

Thank you!