I'm not sure, as the more I read about it, the more it seems like others have had good results applying to bare metal as well. It probably has something to do with my surface prep. It was an older can of paint that had lived in the garage for awhile, but it adhered to the rusted/pitted material just fine. (For now at least. Haha).

I saw a similar issue when I replaced my floor boards, but I just assumed that was because I didn't get all of the oil off the new sheet metal.

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