Dewalt NiCad batteries

Glue bits of 400 grit wet-dry paper to something like a
popsickle stick. You can sand the hard to reach contacts
that way. You can also square the end of the stick
and cut thin strips of sandpaper and hold them in place
on the stick, moving the strip as the different sections
of the abrasive wear down.

Pencil erasers also work.

Ron depending on how bad the corrosion is, there is an electric contact cleaning spray on the market. If it is really bad I would try a plastic gun cleaning brush, I say plastic as if there was any charge left in the battery you could arc (ever so small) across the two terminals.

-- ***Pat*** Rookie woodworker looking for an education!!!