This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
Tarn-X works great for removing oxididation from chip pins without a lot of work or risk in harming the chips. Soak the chips in a shot glass until all black oxidation is gone; then, remove the chips and put them in another shot glass with alcohol to rinse. I use a third shot glass with alchol again to be sure and, then, take out the chips and let dry. By: George Rentovich