What is your metal prep?
What primer do you use under it?
Where do you buy it locally?
2fpower has a great process outlined above.
On most things...
First, I degrease & clean: combination of power washer, Super Clean, Purple Power, Dawn and/or Citriol from Schaeffer Oil. With brushes, putty knife, wire brush, etc. Rinse and repeat.
Second, physically remove as much rust as possible with grinder, wire wheel on drill, power rotary sander, dremel tool, hand sanding, putty knife, trusty Craftsmen screw driver.
Third, degrease and/or clean again, see first step, and/or compressed air.
Fourth, treat with rust remover of your choice, like evaporust or a gel product from the rust store, then spray with phosphoric acid product of your choice to convert as much rust as possible. Reapply as needed. Rinse with water.
Fifth, Rustoleum Rusty Metal Primer and/or Etching Primer. Couple light coats. Sometimes, and only sometimes, use POR 15 instead if it makes sense and is easy enough to get to. (Hate POR15 running down my arm and/or dripping on my head.)
Sixth, Blitz Black, one very light coat, then three light coats. Or, sometimes, POR 15 Top Coat.
Just degreased, cleaned, de-rusted, rust converted, primed and Blitzed -- with rattle cans -- my rear axle and everything attached to it with some confidence it should last another TEN years with occasional top coat touch ups and then I'll think about redoing it. Seems to have worked on other outdoor equipment.
Get Rustoleum from Amazon, buy a case at a time. Purchase Black Blitz online the same way. Closest store with Rustoleum is an hour away and Blitz is well over two hours one way.
Depending on where the parts being painted are, I DO use rattle cans, because "doing it pretty dang good," beats never, ever doing it "perfectly."
Having spent decades around agricultural environments, doing something to clean, paint and prevent rust is almost always better than doing nothing at all while waiting for the perfect solution. YMMV
