Intake Manifold Trumpets...

[SHOZ123]

I was just digging through stuff in the shed. I know there are two intakes with the horns out there.

 

[illSHOyou]

Why are the trumpets zinc coated from the factory? Seems like the trumpets get coated with enough oil in the intake manifold, so why bother?

I assume that acetone or carb cleaner will remove the coating? I need to prepare the trumpets for pipe solder.