Cor-Cote HB Urethane permits rapid return to service for municipal and industrial wastewater treatment facilities, including clarifiers, settling tanks, wet wells, and grit chambers. Immersion can resume within four hours of applying the product on a concrete surface. The low-VOC product is formulated to resist hydrogen sulfide gas permeation and microbiologically influenced corrosion. Sherwin Williams. 800-524-5979.