I'm assuming you didn't wipe the area down with spirits before painting either?

I'm not a painter, but I stayed in a Holiday Inn. Either way, chemical or mechanical the rust has to come off, the metal cleaned and preferably etched and primed (See self etching primer above) then painted in a low humidity environment with a compressor and paint gun. A quick scuff with sand paper, a dusting and a shot w/ a rattle can just won't do it.