In-service water tank painting is possible with the help of moisture-cured urethane (MCU) coatings. MCU tank coating products are quick-drying and easy to apply, while remaining as flexible and enduring as standard tank coating products. MCU tank coating systems have proven their effectiveness in in-service water tank coating applications, and as a result the American Water Works Association (AWWA) awarded MCU coatings with the AWWA D102-03 Industry Standard as OCS (Outside Coating System) 2.
The effectiveness of MCU coatings for damp surface applications is attributed to the foundational isocyanate groups of atoms that all urethane coatings contain. Isocyanate group atoms are reactive to hydrogen-based compounds, such as water condensation found in water tanks. Many tank coating systems also include an intermediate coat mixture containing micaceous iron oxide (MIO) combined with aluminum pigments. The MIO-aluminum mixture overlaps with each other to form a barrier that prevents moisture and corrosive elements to damage the surface. The subsequent out-gassing that occurs from large amounts of surface moisture accumulated during MCU tank coating application can be removed by a simple scraping of pinhole-sized surface damages.
MCU coatings ideally cure at above 35 degrees Fahrenheit temperature. A slower curing reaction at lowered temperatures expectedly occur, although MCU application is still possible to as low as 20 degrees Fahrenheit.