50-Year Corrosion Performance of Metalized Ductile Iron Pipe

Metalizing with high-purity zinc and a topcoat on iron pipe has been utilized for corrosion protection for more than 65 years. This article summarizes a 50-year study of zinc coating on ductile iron pipe (DIP) in one of the most corrosive soils found in the United States: the Florida Everglades. The soil in this area has low resistivity, high potential for microbiologically influenced corrosion (MIC), and a fluctuating tidal salt/brackish water table. In this severely corrosive environment, unprotected DIP experienced complete wall penetration in just a few years. However, metalized zinc-coated pipe with polyethylene encasement did not experience any penetrations during the studies.