DUCTILE IRON UTILITY POLE
In the past 300 years cast iron has been used in every conceivable situation where strength and corrosion resistance was needed. From manhole covers to fire hydrants, water pipe, sewer pipe, bridges and buildings, cast iron has weathered the elements and has survived. With records of hundreds of years of underground and aboveground service, cast iron is noted for its durability.
Ductile iron, which was first used in the 1960's, continues this excellent record of underground and aboveground service. Ductile iron is only different from cast iron in its ability to bend without breaking (i.e., it possesses ductile properties as opposed to the brittle properties of traditional grey cast iron).
Ductile iron contains the same ingredients as cast iron. The difference is not the quantity of carbon (which is what makes steel different from iron) but the configuration of that carbon. In cast iron, carbon is in flake form, while in ductile iron, the same amount of carbon is in nodular form.
Ductile iron, like cast iron, is much more corrosive resistant than steel. In fact, according to our accelerated salt fog corrosion tests, ductile iron has twice the corrosion resistance of Corten Steel (i.e. The corrosion rate of Ductile Iron is half that of Corten Steel once steady state conditions have been reached).
There are many great examples of how long iron lasts above ground. Obvious examples include such everyday items in the utility industry as uncoated manhole covers. These may be used to contain sewage on one side with exposure to water, sun, and even deicing salts on the other side.
Evidence of below grade corrosion resistance is best determined though the local water utility which will have historical records of iron pipe performance for its locality. While ductile iron may last well more than a hundred years, the best source of information about its longevity at your location is at your location! This is due to the wide variation in soil conditions that can have a pronounced impact on the below grade performance of any material. It is safe to say that in all but the most corrosive soil environments (i.e. 95% of all installations), history has shown that unprotected (un coated) iron pipe can easily provide one hundred years or more of service.
Of course McWane Ductile Iron Poles are protected with the best below grade coating for ductile iron structures known at this time. It is a coating called Permasafe that was specifically developed for use on ductile iron and is a derivative of a ceramic epoxy coating used to protect ductile iron in sewer pipe (a highly corrosive sulfuric acid environment) applications.
Ductile iron has excellent mechanical and corrosion resistant properties. It can be formed, machined and heat treated for use in a wide variety of structural applications. Its history of service is unmatched by any other material. It is for these reasons that ductile iron is the material of choice for utility poles in the future.