I agree that powder coat is tough and not affected by rust, my point being that the tough powder coat film does not break down, it stays intact and if water gets in behind it, the metal fails. Paint can do similar but typically the paint film will fail in smaller pieces and start to lose their bond, exposing the oxidation sooner than the powder coat item. I'm only relating my experience with aftermarket coated items such as trailer hitches, running boards, etc.
