(KANSAS CITY, Mo., Oct. 22, 2006) – Tnemec Company, Inc., has introduced a new moisture-cured polyurethane, Series 446 to its Perma-Shield System of coatings formulated to withstand wastewater and fume environments, announced Vaughn O’Dea, technical sales manager, water and wastewater.
“The addition of Perma-Shield MCU offers a superior thin-film protective coating alternative for steel surfaces or miscellaneous metals that would be difficult or impractical to coat with high-build liner or mortar products,” according to O’Dea. “Rake arms, pumps, pipes, cast iron valves, headworks, bar screens and launderers are just a few examples of areas where this product could be easily applied as a uniform film.
“Perma-Shield MCU is also an ideal choice for less severe areas within a wastewater plant, or for smaller localized plants that are not yet experiencing high corrosion rates but still need concrete protection and can’t justify the cost associated with high-build liner or mortar products.”
As the thin-film option in the Perma-Shield System, Series 446 joins a proven line of high-build, 100 percent solids epoxy coatings that includes:
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Series 434 Perma-Shield H2 S, an aggregate-reinforced modified polymer mortar that can be trowel- or spray-applied to deteriorated substrates. It is an extremely durable, low permeation lining that protects concrete against the harsh chemicals and abrasion found in wastewater immersion service. It is especially useful on rehab projects where substantial substrate loss has occurred.
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Series 435 Perma-Glaze™, a spray-applied modified polymer hybrid formulated especially for wastewater immersion and fume environments. Perma-Glaze can be used for three different applications: a topcoat over Series 434 Perma-Shield H2S or Series 436 Perma-Shield FR; a thin-film coating for concrete or steel; and a high-build liner for concrete.
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Series 436 Perma-Shield FR, a spray-applied, fiber-reinforced, high-build liner that provides exceptional corrosion protection for new construction and rehabilitative concrete. Fiber reinforcement adds flexural and tensile strength to Series 436, making it ideal for use in domestic wastewater systems where high abrasion and impact resistance are required. The reinforcing fiberglass also dissipates curing and impact stresses that typically develop in high-build liners, leading to better film integrity and a longer service life.
“The Perma-Shield System is recognized as the gold standard in fluid-applied coating technology for H2S gas permeation and microbiologically induced corrosion found in severe wastewater environments,” O’Dea said. “It also represents a less-expensive, seamless alternative to PVC liners due to its lower cost of application.”
O’Dea cited a growing body of evidence showing the more severe environments found in today’s wastewater treatment plants are degrading thin-film polyamine and polyamide epoxy coatings and causing failures that lead to extensive corrosion. “The Perma-Shield System provides much better resistance to H2S gas permeation than thin film epoxies and easily outperformed coal-tar epoxies (CTEs) in the Severe Wastewater Analysis Test (S.W.A.T.) chamber,” he noted.
S.W.A.T. is an accelerated wastewater corrosion testing program developed by Tnemec and conducted by an independent laboratory that applies Electrochemical Impedance Spectroscopy (EIS) technology to evaluate the level of coating degradation after exposure to a simulated severe wastewater testing environment. “Using electrical current, we can determine the level of coating degradation when exposed to wastewater headspace conditions. Concrete specimens coated with Perma-Shield System linings tested in S.W.A.T. found no blistering, cracking or loss of adhesion after 28 days of exposure,” O’Dea said
In addition to providing superior resistance to H2S permeation, Perma-Shield MCU is hydrophobic, which means it repels water for rapid return-to-service. It features a user-friendly formulation that’s free of coal-tar pitch, is packaged in a one-component kit and is available in four colors: black, gray, blue and red.
Two coats of Perma-Shield MCU will provide the minimum dry film thickness (DFT) of 10 to 18 mils recommended for a porous substrate like concrete. For all Perma-Shield linings, a 1/16” parge coat of Series 218 MortarClad, an epoxy modified cementitious resurfacer, is recommended to fill bug holes, voids and other surface irregularities for a contiguous surface.
“With the introduction of Perma-Shield MCU to the product line, engineers and wastewater facility owners are assured of superior resistance to hydrogen sulfide permeation in moderately aggressive wastewater environments compared to thin-film epoxies and coal-tar epoxies. And contractors will benefit from its user friendliness, flexible application and quick return to service,” O’Dea added.
Series 446 has been used on numerous projects across the U.S., including the WWTP in Oneida, WI; Wyomissing WWTP in Wyomissing, PA; Karcher Creek WWTP in Palsbo, WA; Coeur d’ Alene WWTP in Coeur d’ Alene, ID; a sludge holding tank in Clifton Hill, MO; and Andrews WWTP in Andrews, TX.