Effective Corrosion Control for the 21st Century

Last year, the Ductile Iron Pipe Research Association (DIPRA) conducted a ?usage and attitude? study to determine how iron pipe was viewed within the water infrastructure community, and how we can best address the needs that utilities and their customers face. The results were impressive, and I wrote about them in this very publication (Ductile Iron Pipe: A Review of Usage Study Findings, UIM, October 2014).

While survey respondents rated iron pipe quite favorably for its overall strength, long-term reliability and longevity, performance and lifecycle costs, we learned that we could do a better job at explaining the value of our corrosion control system.

Our nation?s water infrastructure industry faces diverse challenges that can impact our access to clean, reliable drinking water. Much of the existing system is made of cast iron pipe, which has served longer than anyone could have expected. But, we know with modern designs, including corrosion control, we can and do expect the pipe we install tomorrow to serve better than the pipe we are replacing. As a result, corrosion control is often near the top of the list of concerns for utilities. Being diligent in mitigating the effects of corrosion is one simple but important way to ensure the excellent service we have come to expect from ductile iron pipe.

Ductile iron pipe inherently provides solid resistance to corrosion, and in most soils, requires no additional protection. But some soils are aggressive ? an aspect of which our industry has long been aware. We have been conducting research into corrosion control for nearly 100 years, finding effective, economical ways to keep ductile iron pipe?s reputation for outstanding service intact. The most recent innovation is an enhanced polyethylene encasement that builds on the proven technology that has been protecting iron pipe for nearly 60 years.

V-Bio enhanced polyethylene encasement adds an active component to traditional polyethylene encasement by taking advantage of modern co-extrusion technologies in the manufacture of polyethylene films. This technology made it feasible to infuse the film with a proprietary blend of corrosion inhibitor and anti-microbial additives. Moreover, this advancement also ensures that V-Bio enhanced polyethylene encasement meets the requirements set by the American Water Works Association (AWWA) standard ANSI/AWWA C105/A21.5 for strength and durability.

For decades, America has relied on ductile iron pipe to build the finest water infrastructure the world has ever known ? and the V-Bio encasement ensures that ductile iron pipe will be the smart choice for decades to come.

V-Bio enhanced polyethylene encasement is a product that resulted from years of research and development. It is an advancement of the earlier generations of polyethylene encasement, which provided a successful defense against corrosion of iron pipe for nearly 60 years. Research into traditional polyethylene encasement began in 1951, which led to the first installation in an operating water system in 1958. The material was so effective at preventing the corrosion of cast and ductile iron pipe that it is now used to safeguard water and wastewater pipelines across the country and around the world. In North America alone, polyethylene encasement has been used to safeguard hundreds of millions of feet of iron pipe, and it has ensured the integrity and durability for thousands of operating water systems throughout the world. ?

In most soils, ductile iron pipe needs no additional protection from corrosion. This durable pipe material has served for more than 100 years in more than 600 utilities throughout North America, which speaks for itself. In situations where aggressive soils are present, modern pipeline designs incorporate corrosion control as it is important to know how to identify those aggressive soils, and what should be done when they are encountered.

Generally speaking, the types of soils that might warrant the use of polyethylene encasement are soils with low resistivity or that exhibit conditions favorable to the activity of anaerobic sulfate reducing bacteria. One way to evaluate that aggresswiveness of soils is to use the 10-point Soil Evaluation System found in Appendix A of the AWWA C105 standard for polyethylene encasement. In addition, DIPRA worked with Corrpro Companies, the world?s largest corrosion consultant, to develop the Design Decision Model, a risk-based system for corrosion control of proposed ductile iron pipelines by balancing the likelihood of corrosion against the consequences of a corrosion-related problem. This method can evaluate the corrosivity of an environment and make recommendations appropriate to the pipeline under design.

Polyethylene encasement has proven itself to be an extremely effective and economical method for safeguarding ductile iron pipe against corrosion. Traditional polyethylene encasement is a passive system of protection that does not require monitoring or maintenance; and V-Bio adds an active component to that protection.

Proper installation is crucial to ensuring the success of any engineered system and polyethylene encasement is no exception. An understanding of the way this system works and how it should be installed is very important to realizing the benefits of its use. DIPRA is always available to help utilities understand every aspect of the application of ductile iron pipe; including the use of V-Bio enhanced polyethylene encasement.

Corrosion control is an important issue faced by the water industry today. The quality of our nation?s water supply is of the utmost importance to us, and is why we continue to develop new technologies that build on the ability of ductile iron pipe to live up to its fine reputation. V-Bio enhanced polyethylene encasement is another such example of the innovations our industry ensuring that America?s water and wastewater infrastructure can always rely on the strength and durability of ductile iron pipe.

Jon Runge,
CAE, is president of the Ductile Iron Pipe Research Association (DIPRA).

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