Eco-Friendly Tannic Acid-Based Concrete Coating with Anti-Chloride Performance via One-Step Assembly

Chloride ion erosion in seawater is a major cause of durability damage to reinforced concrete structures. Most of the currently used anti-corrosion coatings are organic polymer coatings, which are prone to aging and peeling off and polluting the environment. Inspired by the underwater adhesion behavior of mussels, a green substance-tannic acid (TA) is found and used as the main material of anti-chloride coatings. Three assembly methods of green concrete chloride-resistant coatings fabricated by the oxidative self-polymerization of tannic acid, coordination-driven one-step assembly and multistep assembly of tannic acid (TA), and trivalent iron cation (Fe (III) ) on a concrete surface are proposed. Compared to the other two assembly methods and existing coatings, the one-step assembly of the TA and Fe (III) coating was recommended to be the first choice because of its good continuity; shortest time-consumption (just 10 min); lowest price (only one-third of epoxy coating); and the best chloride-resistant effectiveness per unit thickness reaching 52.17%, far better the multistep assembly method and the oxidative self-polymerization method by 12.67% and 2.42%, which is 79-times higher than that of epoxy resin A. This study offers a TA-based concrete coating fabricated by the one-step assembly method with an excellent anti-chloride performance and cheap price, which is promising for a wide range of applications for the chloride-resistant corrosion protection of steel-reinforced concrete in seawater environments.