Mine has done exactly the same, I am not happy either! The bike is 7 months old what will it look like when it's 2 or 3 ? This is not acceptable IMO
Have you been to your supplying dealer yet - this is something that BMW will resolve!!
http://www.ukgser.com/forums/showthread.php?372935-The-Bad-The-Good-and-The-Ugly!!!
By the way it is not IMO corrosion but simply a fault in the painting process that has affected a limited number of bikes to date