1. Take a Q tip and dip it in vinegar and put it on the corroded area.
2. After it fizzes and dissolves the corrosion take another Q tip dipped in 90 - 99% rubbing alcohol and clean it up
3. Use compressed air to dry it and remove Q tip fibers.
4. Pick out anything remaining with a toothpick and if necessary polish the contacts with either 400 grit sandpaper or a pencil eraser.
John