It was reported recently that the Nikon Repair Center in Taiwan received a damaged Nikkor 17-35mm f/2.8 worth $1800. The lens was accidentally dropped into the sea and damaged by salt water exposure. The repair technicians disassembled the lens and found that the corrosive salt water has caused a coating of rust to form.
This has prevented moving components from functioning properly. The technicians cleaned up the lens by boiling it for fifteen minutes in a chemical solution to remove the corrosion. The lens was fully functional again once they reassembled the autofocus motor and it took about three days to complete the repair process.