So, I wanted to upgrade from my SB-600 in anticipation of some upcoming shoots. I found an SB-900 on Craigslist, met the seller, powered up and fired the flash, and then paid for it. However, upon getting it home the next day, I found some corrosion in one of the four battery slots. Needless to say, I feel pretty stupid for not pulling all the batteries and checking for corrosion--I know how easy it is to store things with batteries in them, only to have the batteries leak over time and damage, if not destroy the device. The flash appears to work just fine, and it does not appear that the corrosion went beyond the powdery type of corrosion. The metal contact in the bottom of the one battery slot has a fair amount of greenish-blue corrosion on it, and I'd like to clean that off ASAP to prevent any problems using the flash as well at to stop the metal tab from continuing to corrode and possibly break off at some point. I cleaned the little bit of powder from the battery slot wall with a q-tip with a little bit of rubbing alcohol on it, but this did not seem to have any effect on the corrosion that's on the metal contact. What would be the best way to clean the metal contact tab? Many thanks!