Try cleaning the electrical contacts on your SB-600 with Q-Tips and a 50/50 mixture of white vinigar and water. Do this until all traces of the corrosion are gone. Then dampen Q-Tips with clean water thougholy to nutralize the vinigar. After rinsing use dry Q-tips to absorb the water. Let the Speedlight dry out for at least 24 hours before installing batteries. With a little luck hopefully it will work. Good Luck and Enjoy your Nikons!