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 ...

For Plastic or Galvanized metal planters, use Stops Rust Universal Bonding Primer ... it should be sanded to give the paint some texture to adhere to. 6. Within the hour or after 48 hours, you ...