Hi, Carl!
24.5.2019
If your silo never gets dry on those short worktrips, and continue rusting the lid and frame,
there is only one radical solution:
Make the lid and its frame, or whole the silo from Marine quality or accid proof
stainless steel.
After paying that, the accid problem is solved…
In the meantime, avoid oak and other “sour” accid-containing woods.