The Design Decision Model® Reveals Longevity of Ductile Iron Pipe

This also appeared on Water Online.

Earlier this year, Maury D. Gaston, manager of Marketing Services for AMERICAN Ductile Iron Pipe and chairman of the Alabama Iron and Steel Council, presented at the 2019 NACE Corrosion Conference on Metallized Arc-Sprayed Zinc Coated Ductile Iron Pipe.

This was the first time in a technical conference or public setting where the criteria and points within the Design Decision Model® were revealed and explained. The Design Decision Model®, which was developed by Corrpro and the Ductile Iron Pipe Research Association, uses points to assess likelihood and consequence of corrosion in the two-dimensional DDM matrix and recommends commensurate actions be taken to eliminate risk and assure sustainability and resilience.

Another noteworthy component of the session was data and photographs from specimens of zinc-coated ductile iron pipe that were buried within the intensely corrosive soils of the Florida Everglades. In these samples, V-Bio enhanced polyethylene encasement was intentionally damaged; and separately, the protective zinc coating was intentionally damaged. The results showed how V-Bio protects against not just externally corrosive soils and bacteria, but also against damaged zinc coating; and how zinc coating protects against damaged V-Bio enhanced polyethylene encasement. “Like hand-in-glove, zinc and V-Bio protect against the most adverse environment to buried pipe,” Gaston said.


This and other specimen from the Everglades were discussed as part of Gaston’s presentation on Metallized Arc-Sprayed Zinc Coated Ductile Iron Pipe.

How Zinc Works With Ductile Iron Pipe

– Zinc provides galvanic protection to iron.

– The topcoat provides a protective layer against exposed zinc and traps zinc oxides to form a protective shell.

– If scratched or damaged, a galvanic couple is created, resulting in continued corrosion protection.

V-Bio Polywrap and Zinc Coating

– V-Bio polyethylene encasement isolates iron from a fresh supply of oxygen thus inhibiting corrosion.

– V-Bio eliminates microbiological cells that can deplete the zinc and attack the iron.

– Not all conditions will require the use of polywrap, but V-Bio provides another layer of protection.

– V-Bio protects zinc, and zinc protects V-Bio.

These developments and test results show how AMERICAN and the ductile iron pipe industry is continuing to innovate and further strengthen an already sustainable and resilient product, adding long-term value to every water system that specifies it.

For more information, contact AMERICAN or click here,