Just a few pieces of information...
All of the "Chrome Clad" (Ford and Chrysler term) or "Chrome Tech" (GM term) wheels that I have seen are cast aluminum wheels with a chromed plastic face glued to the wheel. The face is not removable (or at least, is not meant to ever be removed). There is no steel anywhere in these wheels. I haven't seen the MKX wheel up close, so maybe something is different with that one, but I'm speaking in general.
The reason these chrome clad wheels exist is twofold. (1) Directly chroming a cast aluminum wheel is a very expensive process. Typically, on cars that had optional chromed aluminum wheels, the option cost was $500-800 just for the upgrade from regular aluminum to chromed. (2) Chromed alloys had a lot of problems with peeling in the bead seat area causing persistent air leaks. With the chrome clad wheels, there is no plating in that area (because just the plastic face is plated) and this problem does not occur.
What I think they should do is just change the design so the chromed faces are easily removable. That way, when a problem like this occurs, just the face can be replaced and not the whole wheel. GM's "Fascia Spoke" wheels (which ARE steel wheels under the plastic covers) are like this. The face is just like a normal wheel cover that is easily replaced.
-Andrew L