Definitions for "Galvanic Action"
the action of electropositive and electronegative metals due to the wasting away of the positive metal. This is most noted when iron (Fe) and brass, copper (Cu), or copper (Cu) and zinc (Zn), are in contact in the presence of acid-diluted water.
Flow of electrons which occurs when two dissimilar metals come into contract in the presence of moisture which is capable of carrying electric currents, resulting in the corrosion of the more active metal, which is lower on the galvanic scale, without damage to the more passive metal.
When iron and steel are subject to conditions of aqueous corrosion the incidence and rate at which the corrosion takes place will alter if the steel is coupled with other metals or alloys that are also exposed to the electrolyte. Copper, brass, bronze, lead and nickel are more "noble" and act as auxiliary cathodes to the steel and accelerate its anodic dissolution, that is, its corrosion. Magnesium, zinc and zinc-base alloy are nearly always less noble and tend to divert the attack from the steel to themselves. The galvanic relationship of various metals is an important factor affecting corrosion.