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1/15/2009 | 1 MINUTE READ

The markets: Corrosion resistance (2011)

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Composites continue to provide a superior alternative to metals in corrosive environments. Two standout applications are scrubbers and chimneys in coal-burning plants and cured-in-place-pipe for subterranean water and wastewater management systems.

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The direct cost of metallic corrosion in the U.S. alone has been estimated at nearly $300 billion (USD) per year by CC Technologies Laboratories Inc. (Dublin, Ohio). The U.S. Department of Defense has estimated the annual cost of corrosion in military applications alone at more than $10 billion per year. Corrosion-resistant composites are ideally suited to replace metal structures.

Fiber-reinforced polymer (FRP) is now regularly used to replace expensive stainless steel and high-nickel alloy scrubbers and chimneys (called stacks) that remove sulfur dioxide (SO2) from flue gas emissions in coal-burning plants. In fact, demand is exceeding supply as coal-burning power plants in the U.S. push toward compliance with the U.S. Environmental Protection Agency (EPA) Clean Air Interstate Rule (CAIR). CAIR calls for a reduction in emissions of 70 percent by 2015. One innovative new technology for stack construction involves computer-controlled, stationary vertical winding equipment that can field-wind preprogrammed sections of a stack around a rotating mold. Winding systems are available for tanks up to 124-ft/38m in diameter, according to Robert Brady, of engineering consultancy The Brady Group (Portland, Ore.). As each section is wound, it is jacked up above the mold to permit the next section to be wound using the same mold. This “jack-and-wind” process can be repeated until the stack reaches its design height — in some cases, more than 500 ft/152m.

Cured-in-place pipe (CIPP) is a burgeoning rehabilitation technology that enables repair of deteriorating underground water/wastewater pipelines without expensive excavation. Historically, CIPP processes use tubular, resin-impregnated nonwoven glass/polyester or other fibrous mat that is pushed (via water pressure) or pulled through damaged pipe, inflated, then heat-cured, typically with hot water or steam. The CIPP sleeve adheres to the inside of the host pipe, forming a tough, seamless, corrosion-resistant liner. UV-curable CIPP liner technology, developed in Europe and now gaining attention in the U.S., eliminates the need for hot water or steam cure and the equipment necessary to heat it. UV curing ends concern about the presence of styrenated water in the flow media following cure. International Pipe Lining Technologies (San Diego, Calif.) and Reline America (Saltville, Va.) offer UV-curable liners in diameters up to 48 inches/1.2m. The lining systems rely on stitch-bonded, light-transparent fiberglass fabric wet out with resin formulated with UV-cure photoinitiators.

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