Richard H. wrote:

Another option: Aluminum tape. Used for furnace ductwork; purchased at
the hardware store in a roll like duct tape. It's thin metal foil with
strong adhesive on the back. A great fix for membrane keys that've lost
their conductivity.

Aluminum is a poor choice. When exposed to air it forms a
non-conductive layer of aluminum oxide. Tin or Gold-plated
or even Copper foil would work far better.