Ductile Iron vs Cast Iron Pipe: A Comparison of Physical Properties and Corrosion Resistance

Abstract Ductile iron and cast iron pipe are similar, however there are significant differences in physical properties between the two. Since its introduction, ductile iron pipe has been one of the most popular pipe materials for water systems. While cast iron pressure pipe has not been manufactured in the United States since 1976, it remains a sizeable component of water and wastewater systems across the country as well. Therefore, any efforts related to condition assessment or asset management of metallic pipelines in water systems are likely to encounter both cast and ductile iron pipe. This paper will discuss the material properties of both cast and ductile iron pipe and how they relate to different failure methods for each material. It will also discuss the research that the Ductile Iron Pipe Research Association (DIPRA) has done comparing the corrosion rates of cast iron pipe and ductile iron pipe in the same environments. Graphitic corrosion, unique to iron pipe, will be looked at as well to include a discussion of the strength of these corrosion byproducts in cast iron pipe