Wha t did you use to clean it? I used to wax my chrome along with the painted surfaces until someone told me that waxing chrome causes it to rust.
pitting on chrome is more than likely to be caused by something breaking the super thin chrome surface and working down to the reflective nickel layer. Really bad pitting can come from things such as road salt, sand, abrasive brake dust improperly removed.
I believe the parts you are referring to are aluminum though.
Other parts like Chrome steel wheels usually are plated using nickel then chrome.
Chrome alloy wheels are triple plated: copper to fill pores and provide a better surface for nickel. Then nickel and chrome.
Once something like salt gets through the chrome top layer, it will chemically react with nickel, then the copper (if it's an alloy wheel).
Wax does not cause pitting.