galvanized metal requires pre-treatment before anything will stick, including epoxy, but if it's new, unoxidized or rusted, material, it doesn't need a primer, acrylic paints will adhere well after surface cleaning - pre-treat by washing with soapy water, rinse well, dry, then treat with a weak ammonia solution or strong vinegar solution, rinse again and dry, then sand, wipe well with a tack cloth, and paint
Bill
