Tnemec Company Inc., has introduced a specialized ceramic epoxy lining for the protection of carbon steel and ductile iron pipe used to transport domestic wastewater, according to Vaughn O’Dea, director of sales, Water and Wastewater Treatment. Series 431 Perma-Shield® PL is a 100-percent 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 acknowledged. “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 explained. “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 leading 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. By 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 competitive ceramic epoxy, 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 (ASTM), the British Standards Institute (BSI) and NACE International guidelines.

Abrasion resistance was tested in accordance with BSI BS EN 598: 2007 + A1 2009 for ductile iron pipe, fittings, accessories and their joints for sewerage applications. For this test, a section of ductile iron pipe lined with Series 431 and containing a slurry of pea gravel and water was capped at both ends and placed in a mechanical rocking device, which causes the aggregate to slide back and forth within the pipe to simulate abrasive flow conditions. After 50,000 cycles, the average loss of film thickness along 15 points was 0.6 mils (0.01 mm) for Series 431 and 2.39 mils (0.06 mm) for the widely-used competitive ductile iron pipe ceramic epoxy. After 1 million cycles, Series 431 had an average loss of 5.5 (0.10 mm) mils, while the competitive liner had an average loss of 21.35 mils (0.50 mils).

In ASTM D 4060-07 Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser, coating erosion is determined by the milligrams of film loss when subjected to 1,000 cycles under a coarse abrasive wheel loaded with 1,000 grams of weight. After 1,000 cycles, Series 431 had an average film loss of 76 mg based on three tests performed by Tnemec.

Series 431 also tested excellent for chemical resistance using the NACE TM-0174 Laboratory Methods for the Evaluation of Protective Coatings and Lining Materials in Immersion Service. “After six months of immersion in various concentrations of hydrochloric acid, sulfuric acid and sodium hypochlorite, Series 431 showed no signs of deterioration,” O’Dea added. “There was no blistering, cracking, checking, erosion or delaminating of film. Gloss and general appearance of areas that were immersed in chemicals were the same as areas not immersed.” Series 431 also passed the British Standards Institute (BSI) BS EN 598: 2007 + A1 2009 Chemical Resistance to Effluents test.