Is it normal or usual for the non drive side spacer on a Zipp wheel to corrode after a few years?
Not necessarily normal, but it can happen under excessively moist/salty conditions (i.e. if you sweat lots or if you live near an ocean). Regular cleaning/maintenance of your bike should help prevent this - even just wiping down the bike. If you need a replacement end cap, just give us a call @ 800-447-8372.