Like many municipalities in urban and suburban areas, San Bruno, Calif.’s source water comes both from its own groundwater supply and through a...
New product underwent laboratory tests to prove its strength in corrosion protection
Tnemec Co. Inc. introduced a specialized ceramic epoxy lining for the protection of carbon steel and ductile iron pipe used to transport domestic wastewater, said Vaughn O’Dea, director of sales for water and wastewater treatment. Series 431 Perma-Shield PL is a 100% solids, ceramic-modified polyamine epoxy specifically developed for carbon steel and ductile iron pipe and fittings.
“When properly applied at 40 to 50 mils dry film thickness, Series 431 provides an impenetrable barrier to the elevated levels of hydrogen sulfide gas (H2S) and other sewer gases, which can rapidly corrode ductile iron pipes and fittings used in wastewater environments,” O’Dea said. “This ceramic-modified epoxy lining is for use on new pipe by specialty applicators who understand the unique surface preparation and application process for this product on the pipe and fittings.”
Series 431 was extensively tested for permeability resistance to sewer gases in accelerated laboratory environments using the Standard Practice for Rapid Evaluation of Coatings and Linings by Severe Wastewater Analysis Test (S.W.A.T). “In accelerated laboratory testing for permeation resistance, Series 431 demonstrated performance superior to older coating technology currently used for the interior protection of pipe and fittings,” O’Dea said. “The older ceramic epoxy technologies no longer offer sufficient protection given today’s higher levels of sewer gases, which are the leading causes of coating failure in severe wastewater environments.”
Developed by a coalition of engineers, municipalities and testing laboratories, S.W.A.T. incorporates electrochemical impedance spectroscopy (EIS) to determine the level of coating degradation when exposed to simulated wastewater headspace conditions. Measuring a coating’s resistance as impedance to an electrical current before and after testing provides a correlation to a lining’s overall performance. Higher resistance is an indication of lower permeability to gases, liquids and chlorides, which means more protection for the substrate.
At the beginning of S.W.A.T. testing, coated specimens of Series 431 and a widely used competitive ceramic epoxy both had an initial EIS impedance of 11.2. After 28 days, Series 431 had a final EIS impedance of 10.7, which is in the “excellent” range, compared to a final EIS impedance of 5.7 for the competitor, which is in the “poor performance” range. In the same test, a coal tar epoxy had an initial EIS impedance of 10.9 and finished with a final impedance of 0.0, an indication of no substrate protection.
Other recognized test methods used to evaluate Series 431 for abrasion and chemical resistance were provided in accordance with the American Society of Testing and Materials, the British Standards Institute and NACE International guidelines.