Paint colour for backing plates ?

I've never seen any consistency in galvanizing be it pipe, chain link fencing, whatever. I remember seeing somewhere, a worker was dropping bars of material, aluminum, zink, etc.., in the smelt bath, seemingly at random. its not like he'll taste the soup to know if it needs another pinch of this or that LOL
So I can believe one mans dust shields are a lot more rusted than another's.
Clean them, paint them, or just throw them away. They aren't req'd.