I recently purchased an open trailer to haul my S2000 to and from the track. The axle tubes, leaf springs, etc. are rusted and I'd like to paint them. The problem is, specifically on the axle tubes, which were painted at one point, I'm not going to be able to get it down to bare metal even after I sand it. What can I use that will adhere to a surface that has a combination of metal/rust and old paint? I've ruled out POR15 as it will not adhere to painted sections.