Check eg. Masterbond (a supplier of epoxies and silicones) for details: as corrosion is of special interest, this is one (between many other) topic(s) taken care of.

It will depend on the specific epoxy used, and there are many, many different types with a wide range of different properties, even ones within a group like "electrically insulating". I agree with U. Dreher -- check Masterbond and other manufacturers of epoxies for their different products and the specifications.

Thanks, Dr. Dreher and Dr. Kogler. I checked the website, they provide detailed information on electrical conductivity, but not too much on ion conductivity. I did some literature research. It seems to me that epoxy is not a good ion conductor since it always serves as the non-conducting base polymer in ion-conducting composite material.