Dialectric water heater connection

I noticed a lot of corrosion around the connection between the nipples coming out of my water heater and the flex connectors.

The nipples are regular galvanized steel. Is this corrosion of dialectric nature because the other end of the flex connectors goes into copper pipe? Do I need to use special (dialectric) nipples to prevent this and could this be the cause of a spot leak I just got in one of those (cold inlet) flex connectors? There is no corrosion on the water heater side of the nipples.