Perfromance of Ductile‐Iron Pipe in Soils

Field investigations on underground corrosion, conducted for many years by the National Bureau of Standards, have contributed significantly to the present understanding of the behavior of metals in soil. During the 30 years preceding 1952, data were obtained on 37,000 specimens representing many varieties of metals, alloys, and protective coatings, some of which had been exposed up to 17 years at the 128 test locations throughout the United States. In 1958, new specimens were buried at six test sites to obtain additional information on metals and alloys not completely investigated in the earlier tests. Included were specimens of ductile cast‐iron pipe. Carbon steel pipe was used as a reference material to correlate the corrosiveness of the soil at the six test sites with that of the soil at the 128 locations at which corrosion investigations were previously conducted. Data presented in a progress report indicated that ductile cast iron corrodes at nearly the same rate after a 4‐yr. exposure, with respect to weight loss and pitting, as gray cast iron in the same soil environment, and that the graphite corrosion products of ductile‐iron specimens have the same general characteristics and adhesive properties as those of gray cast iron. This article provides data that presents another point on the corrosion‐time curves after exposure for 8 years in soil at five of the six test sites where specimens of ductile iron were exposed. There are additional specimens, still exposed, awaiting later removal. The article briefly reviews data on the performance of gray iron in the earlier tests.