Washed the S4 this past weekend and discovered that both mirror housings and the trim piece at the rear deck lid have some sort of blotchy discoloration. It's not on the chrome nor on the wheels. The only thing I can come up with is that there is some sort of reaction/corrosion associated with the magnesium chloride used on the roads to prevent freezing.

I washed the car, noticed the blotches then used an auto specific metal cleaner. The cleaner took off the road grim but the blotches are essentially smooth (especially on the mirrors) with the surface of the mirror or trim.

Thoughts?

<img src="http://pictureposter.audiworld.com/69127/mirror_1.jpg">

<img src="http://pictureposter.audiworld.com/69127/mirror_2.jpg">

<img src="http://pictureposter.audiworld.com/69127/trim_1.jpg">

BTW nice car :)

All Metal Restorer and it cleaned the mirrors/trim but would not remove the blotches. I should call Detailers Paradise...

Maybe he knows a way to nutralize it, if it's a chemical reaction.

de