Yeah, but that's aluminum, which doesn't corrode anywhere near as fast as steel.

I have heard it said that clear paint or clear powdercoating can't seal up raw steel anywhere near as effectively as an actual primer that's designed for the job. And for that reason, moisture (and eventual rust) will always creep in at some point, with normal outdoor use where there's rain, snow, puddles, etc.. But is that written in stone? I dunno.