Last fall I rust sprayed my ’68 Fairlane with rust converter, encapsulator, and epoxy primer and after a period of storing it outside under a tarp during the summer I found that it was rusting from under the coatings. I obviously need to go back and sand everything, but I’m not sure where I went wrong in the first place… I did not use any chemical rust stripper, as I sanded down to metal by hand and power tools and I was careful to apply and wipe off pre (as I went) over the entire surface before spraying the rust converter. Everything was sprayed in a heated garage and allowed to cure the appropriate time between coats. I didn’t clean the surface between coats beyond airing them off. While I can’t imagine that over-spray in isolated areas would have ruined the seal on the entire surface, I am curious whether I could have sanded it down and cleaned the surface with something. (I’m pretty sure the instructions said not to use pre on the converter or encapsulator.) I took pictures of most of the process, but I did not get any with the rust encapsulator. Would it be better to have just sand blasted the roof and coated it in just epoxy primer so I could eliminate any potential for surface contamination or is there some simple way to clean the surface between coats of rust converter and encapsulator?