Will in adhere to bare steel?
If you scuff the bare steel (not aluminum)it will usually adhere well, but we always advise to simply do it right and apply a quality primer first. Using 180 grit sandpaper or Scotchpad will do the trick. Make sure to clean the metal good with wax and grease cleaner prior to top coating. We would still recommend spraying down with an epoxy or self etch primer first however.