hmmm, really hard to say if its because of surrouding elements of being outside or if there was some contamination under the primer, even a hand or finger print could cause rust. i think i would start by stripping where the rust is and beyond a few inches to see if there's more underneath. i would think that if its been brewin for 2 years you should see little pits underneath if there's more. how many areas are there? i just worry about down the road if you end up refinishing over something that might haunt you thats y i say consitter just starting over. also when i was in school one of my teachers had said that epoxy only lasts for a year without being top coated? has anyone else heard that before?