The best way to remove rust from painted metal objects is to mix 1/2 cup of baking soda, 1/4 cup of vinegar, and some water, to create a paste. You're then going to cover your rusted object in that paste, let it sit for about 15 minutes, scrub it with a toothbrush, reapply the solution, let it sit for another few hours, and then scrub it away.Web