Surface oxidation, a type of very mild corrosion. It will clean right up and might even wipe off with a solvent and mild abrasive. It takes quite a bit of grunt to sand through the Alclad.
Nothing to worry about, but this is why the factory on QBís, and many builders use a wash primer. Just enough protection to keep this from happening.
It doesnít matter what your environment is, Alclad will eventually show signs of oxidation, it may take many, many years or it could happen in a few short weeks in a bad environment.
Smart People do Stupid things all the time. I know, I've seen me do'em.
RV6 - Builder/Flying
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.