When I had my left front wheel off to install new rotors, we found a patch inside wheel well that was stripped clean to the bare metal by, presumably, a rub from tire.
Tires are 16s and stock size (205 55) and all suspension parts appear solid. Have heard no rubbing under turning. So, not sure how the metal was exposed.
We put a bit of rustoleum on as band-aid.
First, any thoughts on cause?
Second, anybody use any products to inhibit rusting of the now-bare-metal surface?

 

could have happened to the previous owner many tire sets ago I have it too despite my current tires being ok

 

I had some rust in my 75 S door, and Permatex Rust Treatment stopped it cold. You could cover with a good spray undercoating for "permanent" protection.

 

I get it from my17's on the passenger side only. Every couple of months I spray a little touch up paint on the place.

 

I just remembered from when I replaced the tie rod ends that there are stops on the threaded section that limit the travel to the lock position. If they have been moved from factory setting, you could get rubbing with stock equipment and otherwise stock setup.

 

+1. You can stop the rub by a simple adjustment.

 

You may not have a rub while stationary but what about when the tire is under load? My coupe rubbed its rear inside fender wells under hard cornering. I fixed this with some spacers.

 

You guys have the wrong approach. I use my shiny wheel well patches to check my hair everytime I swap out my road wheels for my race rims!