MIMF

In 1982 I made my first guitar, which was supposed to be similar to John Lennon's black Rickenbacker.
I used two DiMarzio pickups and it was full scale with a neck-thru body.
The finish was old Standard Brands spray lacquer.
The pickguard material had white plastic on one side and tortoise shell on the other.
I put the tortoiseshell against the lacquer finish of the body to have the white face showing.
After decades of the guitar in its plush Gibson gig bag, I saw that the pickguard had broken apart and that lots of the electronics had corroded, along with some of the adjoining metal pieces.
There is a ground wire from the tailpiece to the bridge because the bridge I bought had bone inserts and the strings had no ground.
Is it possible that the corrosion came from off-gassing from the tortoise shell against the lacquer finish? Was it a sign of moisture damage?
I know old cellulose film deteriorate in a similar fashion.
I'm refurbishing this guitar and am puzzled how this occurred.
I'm including a picture of what it looked like when I zipped open the gig bag.
Thank you for any help/ideas.
Mike

Nitrocellulose can offgas corrosion inducing compounds that will eat up surrounding materials, including metal. Normally this happens from nitrocellulose plastics (pickguards and binding) instead of nitrocellulose finish. The only way to deal with it is to get rid of the materials that are breaking down or corroding and replace them.