I had a similar problem with my RV-9A wing kit several years ago. Mine sat in a heated hangar for little over a year before I started building them. Most of the pieces had the clear stuff, the rest the blue film. I had corrosion worse than yours. Mine was mostly in the middle and NOT next to the holes or edges. It was so bad it would actually flake. Note however, that there were no signs what so ever of moisture in the crate. All the paper wrapping was dry as a bone and no stains anywhere!! Our EAA chapter happens to have a member who is a FAA DAR. He inspected and did not feel good about them. Enough said for me, so I called Van's and told them what I had and they wanted to see them. So off I go for the 2.5 hr drive loaded up with ALL the skins in the kit in the back of my Expedition. Yes, they actually all fit!
To protect the people at Van's I'll use #1, #2, etc....
#1 knew I was coming so when I arrived we went out to my vehicle to see all the skins. It was pouring rain!! He was rathered mistified over what he saw. Knew something wasn't right, but not really sure what could have caused that since it appeared that the skins would have had to been wet when the film was applied. He calls over #2 for an opinion. Without anything further said other than take a look, #2 proceeds to chew my %^$# and let me know they weren't going to do squat for me. He said I was stupid for not removing the film. I just happened to have MY builders manual handy so I showed him how mine stated to LEAVE IT ON TO AVOID scratches!! He said a few choice words and walked away. #1 was embarrassed about how #2 reacted, so we retreated inside so we could discuss this and come to a resolution. When we came in, he showed me the machine that puts the film on and than starts the discussion. While he is explaining how they would never put the film over wet aluminum, the outside door opens and in comes a forklift with a load of aluminum. Remember, it's raining big time outside and his load of alum is dripping wet. So, as #1 is explaining things, I'm watching this kids run WET aluminum through the machine. #1, who see's I'm distracted by something, turns to see what I'm watching. We are both standing there watching what NEVER suppose to happen.
He turns to me and says, "What can I do to make this right?" It reminds me of that "priceless" credit card commercial! Anyway, I didn't expect Free skins because I let them set for 1+ years, so I more than willingly accepted all new skins at Van's cost....which was really cheap...and besides...seeing his expression was $$$PRICELESS$$$