I put a leather pad over the nipple and a mini condom over the muzzel and everything between stays dry. Keep it dry and corrosion is not an issue. The little condom thingies are available in pharmacies where the bandaids & like stuff are kept. They're called finger cots. Made to keep an injured finger clean and dry. No need to remove the condom it just disappears when you shoot. Old timers with flinters used to put a quill from a feather in the touch hole to keep the charge dry and to indicate that a charge was present in the barrel.