From Fasteners Technology International, April 2014
Anyone that has ever worked on rehabbing an older home has probably encountered a plumbing connection where an old galvanized steel pipe that has been connected with a newer copper fitting such as shown in Figure 1 is in bad shape. The discovery of this condition may be purely accidental, or more likely, if such a connection has been in-place for any length of time, the ticking time bomb represented by this condition has finally gone off and it is leaking or broken.
So what is this condition? It is a classic case of galvanic corrosion. Fastener engineers, designers and end users, especially in instances where metals are being clamped in wet environments, must be very wary of this possibility and make efforts to avoid future problems.