Paint looks oxidized

[SonnyZ4]

My dad sells real estate and has magnetic signs on the sides of his car. He would leave them on for long periods of time (6+ months) and now the paint underneath has an "oxidized" look to it (pics at end of post). The line of dirt in the picture just wipes away, it hasn't been washed in maybe a month when I took it this morning. Washing the car didn't take away any of the oxidized look.

Has anyone ever ran into this and what would be the best route to correct it?

thanks!

http://farm3.staticflickr.com/2859/9542488182_ab94592640.jpg (http://www.flickr.com/photos/93148820@N02/9542488182/)
image (1) (http://www.flickr.com/photos/93148820@N02/9542488182/) by SonnyZ4 (http://www.flickr.com/people/93148820@N02/), on Flickr

[ken tuep]

I would think claybar and polishing should take care of it.

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[lyodbraun]

The paint gets scuffed from that magnet, from dirt and debri that gets in behind it, better clay bar it and then polish it up should take care of it... And tell him to leave the off from now on lol...

[SonnyZ4]

Thanks guys!

Lyod: the only reason I'm even looking to fix the paint is becasue he's finally taking them off for good haha!