Preparation Of Environmental-friendly Marine Antifouling Coatings With Non-leaching Antifouling Agent

Marine biological fouling poses a huge threat to the safe use of ships and marine facilities,and at the same time causes incalculable economic losses.Antifouling paint on the surface of the substrate is widely used as the most practical antifouling method.The use of traditional antifouling coatings is gradually restricted due to the release of toxic antifouling agents to the ocean.In the future,the development of antifouling coatings will pay more and more attention to environmental protection and high efficiency.Tannic acid is a natural compound with good antifouling properties,but its water-soluble properties limit its application in marine coatings.This article introduces a method for preparing an environmental-friendly antifouling agent using tannic acid as a raw material:the complexation of iron ions and tannic acid is used to prepare the insoluble complex ferric tannate,so that it can be used under soaking conditions.It can exist stably in the coating for a long time instead of entering the water body.It avoids the release of antifouling agent.The film-forming material is made of fluorocarbon resin with excellent weathering resistance,isocyanate is used as curing agent,supplemented with other pigments,solvents,and additives,to develop an antifouling paint for marine facilities and ships below the waterline,with good corrosion resistance and weather resistance.First select the film-forming substances and curing agents.An antifouling varnish with excellent mechanical and anticorrosion properties is made with HLR-2 resin and two kinds of isocyanate curing agents IPDI and HMDI.It also needs tetrafluoro propanol to increase the fluorine content of coating surface and reduce the surface energy.The test results show that after the coating is soaked in 3.5wt%NaCl solution for 30 days,the fitting resistance of the coating/metal system reach 1011?·cm~2 order of magnitude,which shows good anticorrosion performance;Calculated by Owens two-liquid method,the surface energy of the coating is about 31.51mJ/m~2.Bacteria and algae adhering to the coating surface have dropped significantly.In this paper,ferric chloride is used to fix tannic acid,a natural antifouling agent that is easily soluble in water,and prepare ferric tannate powder by precipitation method.The obtained ferric tannate powder retains active pyrogallol groups and can exist stably in water.In order to solve the problem of dispersion in the resin substrate,Z6173 silane coupling agent was used to modify the ferric tannate powder.After modification,the surface of the powder is grafted with organic groups,and the water contact angle(WCA)reaches more than 90° and can be uniformly dispersed in the resin.The coating added with modified ferric tannate powder still maintains excellent mechanical properties and impermeability.In the anti-fouling performance test,the antibacterial rate reached more than 80%,and there was almost no algae growth on the surface.In order to improve the dispersibility of alumina and silicon carbide,Z6173 silane coupling agent is used to hydrophobically modify the powder.FTIR experiments and contact angle experiments show that the powder surface is grafted with siloxane groups,and the contact angle reaches more than 90°.Based on the above research,this article adds ferric tannate powder antifouling agent and mica powder,silicon carbide,alumina,polytetrafluoroethylene,melamine cyanurate,fumed silica,titanium dioxide and other pigments to the varnish to prepare a marine antifouling topcoat with excellent mechanical,chemical corrosion resistance,anti-corrosion properties and weathering resistance.Calculated by Owens two-liquid method,the surface energy of the topcoat is about 28.94mJ/m~2,which greatly reduces the adhesion of marine organisms.The iron tannin antifouling agent effectively inhibits the growth of bacteria and algae.In the performance test,the EIS method was used to evaluate the physical shielding performance of the coating.After soaking in 3.5wt%NaCl solution for 90d,the fitting resistance reached 1.49×1011?·cm~2;in the immersion experiment,the coating was immersed in 10wt%sulfuric acid,hydrochloric acid and sodium hydroxide solution for 7d,the surface did not blistering or peeling off,showing good chemical resistance;in the 1000h neutral salt spray test,the coating surface intact no damage,only slightly discolored,showing good weathering resistance;After 720h ultraviolet aging test,the coating did not appear blistering,peeling,powdering,etc.,showing good aging resistance.