It's likely been stored in a container that contained PVC.
Some metals are more susceptible than others to this "rot" and perhaps that's why you're noticing a pattern.
The goo will rinse off with acetone but there will likely be pitting and corrosion underneath.
Some metals are more susceptible than others to this "rot" and perhaps that's why you're noticing a pattern.
The goo will rinse off with acetone but there will likely be pitting and corrosion underneath.





















