Thanks for pictures - now I know what to look for.
There is a clear coat on the polished al. It looks as if the surface is "broken" and the al starts to corrode. This is common for polished rims with clear coat - but not after a couple of months.
One possibel explanation is that the boss is too big,and will damage the clear coat when installed.
Front wheels "worst" probably because of aggressive brake dust - don`t brake
