In this picture is a bolt that was removed from with the xyz switch. I am curious what would cause this bolt to develop its white deposits. Of the two bolts removed only this one was this way.

 

You forgot the picture.

 

Its invisible lol no pic

 

Im betting it is corrosion. Is it almost a powder?

 

Maybe this will work

xyzbolt_zps1be7b360.jpg photo by saidrover | Photobucket

 

Thats corrosion.
Do yourself a favor, go back to your Photobucket pic and copy the "img code" and then paste it in your post.

 

More than likely from parking here.

 

LOL!!!
But thats the beauty of a Rover, you can park anywhere.

 

Brass is an alloy of copper and zinc and there are numerous variations as to the mixture of the copper and zinc which produces many types of Brass...
Brass will eventually corrode depending on its mixture and what it is exposed to however the speed of the corrosion process may take decades or even centuries but as expressed above if you park your rover in this sshh it will happen quicker.