Utah isn't really known for having major rust issues like states like Michigan, Ohio, New York, etc in the rust belt.
I'm in Oregon where we don't use road salt in the winter and my steel driveshaft is pretty rusty. It's nothing to worry about unless it gets pretty excessive into the parent metal (the shaft's steel itself).
If you were wanting to try to eliminate any of the surface rust you've formed, you can always take a grinder with a wire wheel attachment to eliminate the rust, then rattle-can on a automotive primer then a black enamel rattle can of some sort. That POR15 is kind of overkill IMO in a mild environment like Oregon or Utah where rust isn't much of an issue.
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