your best bet is electrical contact cleaner i guess. I have used it on my cards from time to time. As well as my keyboard a number of times.
Also to prevent corrosion from forming in the future. When you use a peltier use dielectic grease on the pins to prevent any moisture from forming. You may have to wiggle the cpu around a bit to get a good connection after you apply it. But that will insure you do not form moisture underneath the cpu.