Application Of Mussel-Inspired Biomimic Coating Based On Tannic Acid In Concrete Anti-Corrosion

Durability damage is one of the significant problems in reinforced concrete structures in coastal and offshore projects,and chloride induced corrosion is a major cause.Chloride induced corrosion is essentially the process of chloride ion diffusion in concrete.In practice,measures such as adjusting the mixing ratio of concrete,adding corrosion inhibitors or rust inhibitors and adopting anti-corrosion coating can be applied to delay the diffusion of chloride,thus prolonging the durability service life of the structure.Among these measures,adopting anti-corrosion coating is effective,easy to construct and maintain,and can be used in combination with other measures.Inspired by mussel adhesion,tannic acid is used as the main material to mimic mussel adhesion.Coatings are constructed through tannic acid oxidation self-polymerization,one-step assembly of tannic acid and iron(III)ion and coordination-driven multistep assembly of tannic acid and iron(III)ion on concrete surface to improve the chloride resistance of the concrete.By analyzing the results of the electric flux test and the surface microstructure,the multistep coating is determined to be most applicable.The influence of reaction conditions on the coating and its mechanism are studied by electric flux experiments,scanning electron microscopy,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy.For the multistep coating with the best effect,the long-term stability of the coating effect was studied by natural diffusion experiment of tidal circulation.Based on the test results and previous research results,a chloride ion diffusion model considering effects of coating,heterogeneity of the concrete and block effect of the embedded steel bars is established,and then the influence of different measures on the durability service life of concrete was analyzed according to the model.Compared with commercial coatings,the multistep coating manifests a comparable effect of reducing chloride penetration,and exhibits excellent chloride-blocking efficiency.The coating is stable in the tidal environment,and is very promising to become green and environmental-friendly anti-chloride coating for concrete.