Aluminum is in fact harder to plate than steel, but that's not an acceptable excuse for Harley to keep having chrome problems with their wheels, mirrors, and other chromed aluminum parts. When done properly, in a properly controlled process, plating on aluminum is durable. When done on the cheap, in poorly controlled processes, the plating is prone to rapid failure. Guess which approach Harley takes, top quality or cheap procurement cost?
Harley should take care of the problem under warranty. Be prepared however for the "salt air" BS excuse they have used on so many others who live near one of the oceans. I've even heard of them trying to pull that crap on a guy who lived in Atlanta. Last time I looked at a map Atlanta isn't exactly a beach community.
Jerry