Zinc and Its Alloys

Zinc is not commonly used without supplemental corrosion protection for corrosion resistant applications since zinc is located near magnesium on the Galvanic Series, and is thus very susceptible to corrosion. It is therefore very anodic to most metals, and will corrode preferentially when galvanically coupled with metals that are more cathodic. Often it is used as an anodic coating to protect steel from corrosion. It is also used as sacrificial anodes for ship hulls, pipelines and other applications. Furthermore, zinc can act as a barrier coating that is resistant to mechanical and electrochemical degradation.

Impurities have a significant impact on the corrosion resistance of zinc, as  they often cause the surface to be more susceptible to corrosion. Some impurities, however, such as aluminum, may result in slight improvements in the corrosion resistance of zinc by forming a protective film on the surface.