Advanced materials and coatings for corrosion intensive components at water treatment plants: Fid-Bau Portal

Advanced materials and coatings for corrosion intensive components at water treatment plants

Stephenson, L.D. / Kumar, Askok

Components of potable WTP (water treatment plants) are susceptible to corrosion due to constant immersion in water and proximity to chlorine environments. An Army WTP was constructed during 1940-1950, and many components are nearing the end of their design lives. Water treatment plants at other Army Installations also face these corrosion problems. In addition, similar corrosion problems are present at water treatment plants at other installations in the DoD (Department of Defense). The repair project had the following objectives: Restore the water treatment plant to optimum operating conditions using advanced materials selections. Select and implement corrosion-resistant coatings for metallic components and restoration coatings for concrete filter tanks. Develop Industry or Government Specifications and Standards and Implementation Guidance for other DoD Installations. Emerging coating systems employed in this project were: ML-72 microsilica sprayable restoration mortar (System A), DS-4 coal-tar epoxy (System B), 1103 coal-tar epoxy (System C), 1312P epoxy putty (System D), 1312S epoxy (System E) and 1450 urethane (System F). Metrics for the project are based on verification of the atmospheric corrosivity of the WTP. A set of eight coupon racks were installed, each having eight uncoated carbon steel coupons. The coupons were precisely weighted and inscribed prior to placement. The intent of the coupons is to be able to accurately monitor the corrosion rates in the various environments. The results of the project demonstrated that: 1. Microsilica cement mortar and epoxy based coatings approved for potable water according to NSF Standard 61 applied to the filter tanks forms a high strength moisture barrier with extremely low permeability and a strong chemical/mechanical bond to brick and cementitious substrates. 2. Coal-tar epoxy coatings approved by the AWWA (American Water Works Association) are efficacious in the presence of moderate concentrations of airborne chlorine gas that is used in water treatment facilities. It is noted that these corrosion prevention and control technologies have only been in place at the Army Installation water treatment plant for 1 year, and their long term efficacy remains to be validated.