Engineers specified the four-coat polyurethane system 13 years ago because it would withstand the rigors of hot and cold temperature extremes, air pollution, acid rain, and virtually anything Mother Nature would send its way. The coatings, manufactured by Tnemec Company of Kansas City, MO., were formulated with Desmodur polyisocyanates from Bayer MaterialScience. According to Tnemec’s Sean Carlin, the coatings were expected to perform well for at least 20-25 years. This was an important consideration, since the Municipal Authority wanted to be sure the water tower would not only look good, but also require little maintenance.
The coating process began at the Clive, IA, fabricating plant of Pitt-Des Moines Inc. Crews blasted the tank’s exterior plates to SSPC-SP6 standards, then sprayed on Tneme-Zinc 90-97, a zinc-rich polyurethane primer. This primer not only provides excellent exterior corrosion resistance, it protects the inside dry areas of the water tank as well.
Once the tank was erected in its permanent location, painting contractor Neumann Company Contractors, Inc. of Romeoville, IL, took over. The weld seams were blasted to surface prep specifications, and the primer was touched up wherever necessary. The exterior plates then received two coats of Tnemec Series 73 Endura-Shield aliphatic acrylic polyurethane, which provided a semi-gloss finish and long-lasting color retention for the white and pale blue pigments. A topcoat of Tnemec Series 76 Endura Clear high-gloss polyurethane was applied last, bringing the total polyurethane coating DFT on the tank’s exterior to 7.5-11.5 mils. In all, the Neumann crew painted 104,300 square feet of steel with approximately 900 gallons of polyurethane coatings.
Nearly 13 years later, the coating system on the Robinson Township water tower is still corrosion-free and in excellent condition. MATR is just as satisfied with the coatings today as it was back in 1994. Carl Angeloff, P.E., head – NAFTA Business Development and Manager – BD Corrosion, Bayer MaterialScience, notes, “Since this water tank is located close to the Bayer MaterialScience headquarters, we’ve been able to observe the performance of the coatings first-hand on a regular basis. I must say, the finish still looks picture perfect – and should stay that way for at least another decade.”
For more information, visitwww.tnemec.comorwww.bayermaterialscience.com.