In treatment facilities processing large quantities of water and wastewater, concrete is exposed to a harsh environment. Coatings help protect the concrete and prolong the life of the facility. They must be able to protect the concrete from attack by chemicals such as acids, sulfates, sugars, and fermenting liquids. Coatings that have proven particularly successful after sustained use in the field include epoxies, coal tar epoxies, and vinyls. Epoxies provide an extremely hard, durable finish for concrete. Coal tar epoxies are economical and develop good adhesion to concrete. Vinyl coatings dry fast and aren't temperature dependent for curing.
The performance of any coating system is strongly influenced by concrete surface condition. Laitance should be removed with light abrasive blasting or acid etching before applying the coating. Efflorescence should be removed by scrubbing or with muriatic acid etching. To remove form oils, scrub with an emulsifying agent and rinse with tap water. Bugholes should be opened up with light abrasive blasting. The surface should have the texture of medium-grit sandpaper and should be tightly adherent, not powdery. Most coating manufacturers recommend coating concrete no earlier than 28 days after it's been placed.