Graphite and carbon bottom out the list, being the most highly charged metals. This is the most common form of corrosion found on fiberglass boats, and is the least understood. Electrical currents are generated anytime there is a change in chemical composition. That's why powerful explosives can be made of such ordinary things like plastic. As its name implies, crevice corrosion involves water, metals and crevices.
Crevice corrosion is the same thing as galvanism, only it occurs under different circumstances.
Crevice corrosion on screws. The one on the right shows the typical wasting of the shank right under the screw head. The one on left was exposed to water both under the head, and on the inside of the hull where it has thinned at both locations. This is probably what the bolt in the photo below would look like when removed. If no oxygen source is introduced, the corrosion process continues until the metal is completely gone.