Study On Anti-Corrosion And Anti-Fouling Coating Systems In Environmentally Friendly Marine Environments

The increasing means and demand for expanding marine resources have made it even more urgent to address the issue of marine corrosion and fouling.The economic losses caused by marine corrosion each year reach 1%or more of China’s annual GDP（accounting for 1/3 of the total corrosion losses）.The economic losses caused by marine pollution every year cannot be underestimated,but what is more serious than the economic losses is the waste of human resources and huge security risks caused each year.Deeper research on marine corrosion and fouling can help us find more effective,environmentally friendly,and sustainable measures to avoid or reduce economic losses and safety hazards.In this study,an environmentally friendly anti-corrosion and antifouling coating system for the marine environment is proposed,which uses the modified liquid polysulfide rubber low zinc content bimetallic epoxy anti-corrosion coating as the anti-corrosion primer,and the completely environment-friendly and non-toxic 7-amino-4-methylcoumarin modified phosphorescence fluorescent antifouling gel as the antifouling layer.The specific research contents are as follows:（1）A silane coupling agent KH560 was used to undergo a ring opening reaction with liquid polysulfide rubber to obtain a silane terminated liquid polysulfide rubber（modified rubber）.A modified liquid polysulfide rubber,bimetallic（zinc and titanium）fillers,carbon nanotubes,and epoxy resin were compounded to obtain a coating with good salt spray resistance and strong adhesion to the substrate.Tests such as adhesion,SEM,salt spray test,and EIS showed that the modified liquid polysulfide rubber bimetallic salt spray resistant epoxy coating had excellent adhesion to the substrate,a dense structure,good corrosion resistance,and anti-foaming performance of the coating.After 1440 hours of neutral salt spray testing for a single coating,the coating surface was completely free of rust and blistering,and the corrosion diffusion width in the marked area has decreased from 7 mm to1.7 mm compared to pure epoxy coating.The coating has excellent resistance to salt water immersion,greatly reducing the amount of zinc used compared to epoxy zinc rich coatings.The optimal formula contains only 28.6%zinc metal added to the coating,and only 0.5%reaction products precipitated after immersion in salt water.The coating has no blistering phenomenon,it is a long-term anti-corrosion coating that is expected to be used both in the atmosphere and underwater.（2）A composite antibacterial agent was designed to store energy by the phosphorescence effect of rare earth oxides,emit light at night and excite 7-amino-4-methylcoumarin to produce fluorescence and prevent algae from adhering.The performance of its composite with PVA hydrogel was studied,and an all-weather autocatalytic phosphorescence fluorescence sewage gel material was obtained.The rare earth phosphor powder was prepared in a high-temperature tubular furnace,and then coated with Si O₂ for waterproof treatment,and then grafted with 7-amino-4-methylcoumarin to obtain a composite antibacterial agent with phosphorescence fluorescence effect.The composite antibacterial agent was added to PVA hydrogel to obtain a hydrogel complex.The bacteriostatic test results of 7-amino-4-methylcoumarin modified phosphorescence fluorescence anti sewage gel showed that its bactericidal rate against both gram-positive and gram-negative bacteria was above 99.98%,the fluorescence staining experiment showed that the coverage rate of dead bacteria reached 41.61%.The tensile strength of anti-sewage gel can reach 1.49 MPa,which can meet the strength requirements in real sea environment.The algae adhesion test shows that the algae coverage area of the composite hydrogel under natural light is only 2.67%,only one tenth of pure PVA hydrogel.It has good anti-pollution and algae suppression performance,which is due to the fact that the rare earth phosphor powder after sunlight can provide light source for 7-amino-4-methylcoumarin continuously at night,and stimulate 7-amino-4-methylcoumarin to generate fluorescence response for a long time to prevent algae adhesion.The anti-corrosion and antifouling coating system in an environmentally friendly marine environment has excellent anti-corrosion and antifouling properties,and is expected to be applied to seawater immersion parts of large components such as cross sea bridges,large underwater oil wells,and gulf ports.The same anti-corrosion primer can be used for underwater components,reducing the difficulty in process management of component coating construction in marine environments,while providing a new choice for anti-corrosion and antifouling of underwater components.