With the growing emphasis on environmental compliance nationwide, 100 percent solids epoxies and polyurethanes are replacing solvent-based coatings for long-term corrosion protection of steel and concrete potable water storage tanks. In New York, where the maximum contaminant level (MCL) for organic solvents such as xylene is set at 5 parts per billion (ppb) in drinking water, Tnemec has specified that only 100 percent solids epoxies and polyurethanes be used in place of solvent-based coatings for potable water tanks.
“More than 85 potable water tanks in New York have been lined with 100 percent solids epoxies and polyurethanes from Tnemec,” according to Doug Hansen, director of sales, Water Tank Market. “All of these projects have succeeded in meeting New York’s stringent MCL requirements.”
Series FC22 Epoxoline and the new Series 22 Epoxoline are 100 percent solids, thick-film epoxies certified by NSF International in accordance with ANSI/NSF Std. 61 for use in potable tanks and reservoirs of 5-gallons capacity or greater. They can also achieve the required dry film thickness in a single coat, which helps to keep labor costs down while enabling a quick return to immersion service.
Series 406 Elasto-Shield is a fast-setting, 100 percent solids aromatic polyurethane hybrid lining recommended for immersion service in water and wastewater treatment. Series 406 is also certified by NSF International in accordance with ANSI/NSF Std. 61 for use on the interior of potable water storage tanks and reservoirs of 50,000-gallons capacity or greater and pipes 35 inches in diameter or greater.
Although they share the same name and number, Series FC22 and Series 22 are dissimilar in their intended usage and method of application. “For varying weather and seasonal conditions, Series FC22 has the ability to cure down to ambient temperatures as low as 35 degrees F,” Hansen explained. Series FC22 is heated and applied using plural component equipment, which is an effective method of application on elevated water towers.
“The new Series 22 will be somewhat limited to ground storage tanks and water treatment facilities if conventional application equipment is utilized,” Hansen noted. “Series 22 can be applied using a conventional 56:1 airless spray pump to achieve 16 to 30 mils dry film thickness (DFT) in a single application for excellent chemical and abrasion resistance. By eliminating the need for plural component spray equipment, the application cost per square foot is reduced.”
A specialized curing mechanism in Series 22 Epoxoline allows for faster cure response so that blast cleaning can continue from one day to the next without abrasives being embedded into the previously coated section of the tank. “Series 22 Epoxoline cures almost twice as fast as the formulation it replaced,” Hansen added. “The new Series 22 also has an extended spray life compared to the older technology. And return to immersion service is five days compared to seven days for the older formulation.”