While you're at it, sand all the other areas you treated for rust to smooth them out and prepare them for painting. Any spots you've sanded down to the bare metal must be primed before you paint ...

while rusty or painted metal may need a more intensive mechanical or chemical cleaning. The second step in preparing and cleaning metal surfaces is to choose the appropriate surface preparation ...

We are a chemical dipping company that removes paint and rust from ... the acid does attack the metal slightly. Then it'll be pressure washed until all of the rust is removed.