We’re currently having some paint warranty work done on the dome of our courthouse (I’m the maintenance tech there, the dome was repainted about 4-5 years ago). There were various processes used based on the prep regimen (which was based on thickness of the metal substrate and cost). Anyway, on the thicker metal, it was “vapor-blasted” back to bare metal, a clear, 2-part, epoxy primer was used, then a tinted, 2-part epoxy intermediate coat, then a 2-part urethane topcoat. Where the prep and process were good, the product is near bulletproof. However, there were some holes missed that rusted, among other things like a rush to beat impending winter or deadlines…hence the warranty work.