RE: Painting Galvanized metal.
Id suggest starting by blasting it with a big (3500psi / 3.5~4.0 gpm) pressure washer with a 15 deg nozzle up close and personal.* That will remove anything that is loose or wanting to peel or flake soon.* I would follow that by scrubbing with TSP (trisodium phospate with some bleach added to remove or kill any algae growth.* Follow with etching*with a muriatic acid or metal prep solution, rinse, then zinc chromate primer.* Then finnish paint to suit.* It sounds like a lot of work but isn't to bad really,just a lot of steps.* I'm believer that it easier to do something well, than do it over,* JMO*