There was an earlier post about 'unusual' loud noise when rock is kicked up hitting the wheel-well area...

I am an Infiniti newbie. This weekend when I was washing my car I noticed that the exterior wheel-well area is not undercoated or lined. That would explain the 'loud and distinct' sound when rock hits it.

These area in my MB's have a plastic lining so it'll dull the sound from rock hitting it.

More materially though, is there any rust concern at the wheel wells since it's painted (but bare) sheet metal?