I've found wiping weapons off after handling is a must, in humid Mi. I have an old silicon-infused cloth for that purpose on top of my safe, it's quite old, but still works. I use any cloth on hand to wipe off my guns when touched by human hands. Must be acids that cause corrosion. I learned this yrs. ago, after showing my Gold Cup to a friend. Must have forgot to wipe it off,. Next time I looked @ the G.C., there was a fingerprint corroded just below the ejection port. & yes, it was just deep enough to
pit the metal. Bit the bullet & immediately ordered a new stripped slide, transferred parts off the old one when it arrived. Glad I did this. 'cause later, I priced a slide & was shocked @ how the price had increased.. Anyway, the lesson was learned.. ( & also why I prefer SS pistols)