Cast Iron Pipes
This information reflects our best understanding of product composition in 2015.
“Cast iron” is a generic term for product made by pouring molten iron into molds where the metal is cast in the shape of the mold. Ductile iron pipes are one such cast iron product. Standard industry practice is to use 100% waste scrap...
“Cast iron” is a generic term for product made by pouring molten iron into molds where the metal is cast in the shape of the mold. Ductile iron pipes are one such cast iron product. Standard industry practice is to use 100% waste scrap iron and steel for these castings, and add a small amount of magnesium, which gives the finished pipe its ductile qualities. The liquid alloy is poured into a centrifugal mold and spun at a high speed to form a pipe of the desired dimension. The metal cools quickly, becoming solid, and is removed from the mold and tempered to increase it strength. Because the bare iron casting is vulnerable to rust, standard practice is to coat all surfaces of the pipe while at the factory. The exterior of the pipe receives a pre-finish of zinc, and an asphaltic coating to seal out moisture and other corrosive elements. Pipes intended to carry sewage or wastewater are coated on the inside with a high alumina cement, a specialty cement resistant to the corrosive properties of these effluents. (Pipes carrying potable water would be lined with a standard Portland cement). The asphaltic coating used on the pipe exterior can also be applied to the interior of the pipe walls if water chemistries necessitate an additional protective layer. Depending on soil characteristics (pH, permeability, etc), the pipes can be installed below grade with a protective polyethylene sleeve surrounding the pipe.