I'd pressure wash [with chemicals}...let dry and apply a galvanized primer.{if needed}
Then top coat with a Devoe DTM product: Devflex HP
It says you don't need a primer if prepped properly..I'd look into that...
General Description:
A premium quality, direct to metal acrylic semi-gloss enamel for high traffic interior-exterior areas of commercial, institutional, residential and industrial structures. Features a non-yellowing film with excellent durability.
Typical Uses:
May be applied directly to interior or exterior steel and aluminum, and to properly prepared galvanized metal, wood or masonry surfaces.
Advantages:
- Alkyd-like hardness and durability
- Excellent color retention
- High hiding
- Non-yellowing
- All purpose finish for multiple surfaces
- Excellent resistance to grease, oil and water
- Excellent flow and leveling
- Resists peeling and chipping
- Low odor and water clean-up
- Washable and scrubbable
- Good abrasion resistance
- Easy application - brush, roll or spray
- May be applied direct to steel and aluminum
Devflex HP