When it comes to preventing ductile iron pipe systems from exterior corrosion, polyethylene encasement (Polywrap) is an effective and economical form of protection. Standard Polywrap has been used as a proven system to prevent exterior corrosion for several decades — and recent advances have taken this already strong system and improved upon it even more.
Standard Polywrap works by creating a barrier between potentially corrosive soil and the surface of the pipe, as well as building a dielectric barrier to stop stray currents in the soil from damaging the pipe.
An advanced form of Polywrap has been developed to contain additional corrosion fighting capabilities. This new form of Polywrap is known as Enhanced Polywrap. Enhanced Polywrap is a 3-layer co-extruded linear low density film that is fused together to make a total thickness no less than 8 mils.
The inside layer of the film that meets the surface of the pipe is infused with two key ingredients. The first is a volatile corrosion inhibitor (VCI). The VCI mixes with any corrosive liquids that may seep between the wrap and the pipe and neutralizes them. The second ingredient is an antimicrobial additive, which reduces or eliminates the growth of any sulfate-reducing bacteria that may be present. Sulfate-reducing bacteria is known to cause some levels of corrosion — by creating an environment that does not allow them to grow or even be present, this form of corrosion is also prevented.
AA Thread has developed VB3 Enhanced Polywrap. When testing the Enhanced Polywrap side by side with standard Polywrap, third-party lab the results showed that not only did the VB3® Enhanced Polywrap have a reduction in bacteria by over 99 percent, but the standard film showed a level of growth of bacteria.
The VCI effectiveness was also tested by using test method BSI IEC 68-2-30. Metal cards were placed in with a very corrosive solution for seven days. The metal cards with the VB3 Enhanced Polywrap film showed no signs of corrosion at the end of testing. The meal cards with no VB3 Enhanced Polywrap film showed corrosion just 3 days into the testing.
In addition to the previously mentioned tests, the film must meet all the current standards outlined by ANSI/AWWA C105/A21.5 specifications. AA Thread’s VB3 Enhanced Polywrap not only meets all these standards but in most cases far exceeds them. The material is made in the United States with 100 percent virgin polyethylene. WW
AA Thread has been in business since 1979, supplying wholesalers and distributors in the water/wastewater and plumbing industries with quality products and service. Its products include polyethylene encasements for ductile iron pipe, pipe wrapping tapes, detectable/non-detectable tapes, PTFE thread seal tapes, sealants, and more. Learn more at www.aathread.com.
Published in WaterWorld magazine, November 2022.
