I assume you mean corrosion on the *inside*? There is a (coated) metal sleave inside the G2/G2Z lights. However, I think you are right about them being much less prone to corrosion. However, I suspect the reason is the battery chemistry, not the amount or location of metal.

FWIW, I've also had several Mag lights die due to corrosion issues. I keep 123A based lights in my car (worst case I think) and have never had a problem.

I think I've read that alkalines tend to get pretty flaky once they've discharged. I think the key is that you want put fresh batteries in a "car" type light fairly often. My guess is 1 year MAX (if you don't use it).

-john