When designing a drainage structure, one of the most important aspects that an engineer must consider is the durability of a material and the estimated service life that material will provide. A recent study conducted by the National Corrugated Steel Pipe Association (NCSPA) is an effort to provide more information to engineers and specifiers on the expected service life of polymer coated steel pipe. With support from the American Iron and Steel Institute‘s (AISI) Steel Market Development Institute‘s (SMDI) Construction Market Council (CMC), the NCSPA conducted an extensive field research study assessing the condition of polymer coated corrugated steel pipe installations that have been in-service for an extended period of time, some nearly 40 years. The results of this study conclude that polymer coated corrugated steel pipe will provide a service life that exceeds 100 years in normal as well as severe environmental conditions.
The research in this report covers inspections of over 50 individual pipe sites in 5 states. The sites are located near Albany and Lake Placid, New York; Madison, Green Bay and Long Lake, WI; northeastern Arkansas; up to the Upper Peninsula of MI; and down to the bayous of Louisiana.
Polymer coatings for corrugated steel pipe were first introduced in the 1970’s. At the time, several different types of polymer coatings were available. Of these polymer coatings, TRENCHCOAT Protective Film, developed by the Dow Chemical Company, is the focus of this study. The tough and durable polymer film is bonded inside and out to a galvanized steel sheet coil prior to the corrugation forming processes. The full product specification can be found in ASTM A742, Polymer Precoated Sheet for Sewers and Drains and AASHTO Materials Specification M245. This coating has been subjected to a battery of testing over the years through chemical resistance testing according to ASTM standards and comprehensive field studies of installations throughout the country.
This report concludes that the majority of the polymer degradation occurred due to external damage, and there was no indication of a breakdown of the coating over the length of the pipe. The coating performance observed in this study further validates a significant extension of service life for these pipe and support industry guidance of an “add-on” life of 80 years to the underlying galvanized pipe, even under severe environmental and abrasion conditions. The NCSPA will continue to study this material, but the indication from this research is that polymer coated corrugated steel pipe is an economical solution for engineers providing a material that will exceed 100 years service life, even in demanding environmental conditions.
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For more information on this and the many other benefits of Corrugated Steel Pipe, contact us by calling (972) 850-1907 or visiting NCSPA.org.