Assuming the galvanised poles are bare, clean, dry, sound and prepared as detailed in the technical data sheet you could consider Rust-Oleum 3302 CombiPrimer Adhesion Primer followed by two coats of Rust-Oleum CombiColor Original.

This can be mixed to many RAL, NCS or BS colours in a satin or gloss finish.

If you have some rusty steel, the rust be removed before any application. 

For bare prepared steel should be primed first with Rust-Oleum 3369/3380 CombiPrimer Anti-Corrosion then two coats of Rust-Oleum CombiColor Original.