You'll just have disconnect the battery and pull each fuse and check for corrosion. While you are at it check any relays, too.
Never had corrosion problems with fuses with any car I owned. Kind of odd you are seeing corrosion. Is the car water tight? Any water leaking into the cabin?
With older cars a leak source can be the doors. The door membrane that separates the wet side of the door goes bad -- age -- and lets water over into the dry side. This can leak out the bottom of the door into the cabin.
Check for dampness at the bottom of the doors and the carpet next to the doors.
My habit as my cars get older is after every wash or after driving in the rain to check the doors/floor carpet for dampness.