I found with the first wing skin that my fingers left prints on the surface that won't clean up. I think even a little salty sweat on your fingers etches (corrodes) the surface. It is probably shallow, but...
Anyway, on the second wing I decided to use white cotton gloves (flimsy ones that industry uses for the same reason). I bring home used ones from work. I don't bother with them on the frames, since they all get anti-corrosion treatment.
Then before I hung up my wings in the other (unheated) side of the garage, I wiped the skins with window cleaner and wrapped them in a clear plastic sheet. I did this mainly to keep the wing from filling up with dust inside. I won't know how well this has worked until I take them down to do a test fit of the flaps and slats when I'm done with these in about a month (I think).
Zenith says that 6061 is relatively corrosion resistant, and I believe that. On the other hand, if the aluminum is exposed to water and there are other contaminants on the surface (like salt from sweat or other kinds of "dirt"), then a chemical reaction takes place to etch or dissolve the aluminum. And the bi-products of this reaction are corrosion.
I cleaned my tail surfaces before I hung them in the heated garage. They get dusty, but otherwise look okay. We'll see how the wings do.
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