Alu top box - staining

[oly]

After only one trip my aluminium top box has becomed stained
on the back where the road crap splashes up. It will not clean off
Has anyone any suggestions on how to clean the aluminium without scratching it?

 

[MikeP]

Search facility is your friend.........

http://www.ukgser.com/forums/showthread.php?t=88480&highlight=pannier+corrosion