Study On Preparation And Corrosion Resistance Of Functionalized Graphene Oxide Waterborne Composite Coatings

The marine environment is an extremely harsh corrosive environment.In order to adapt to the rapid development of my country’s economy,corrosion and protection in the marine environment are imminent.Among the existing corrosion protection methods,coating protection on the material surface is one of the effective and costeffective ways.Compared with oil-based organic coatings,waterborne polyurethane(WPU)coatings,using water as the dispersion medium,have excellent flexibility,wear resistance,weather resistance,environmental protection,non-toxicity and sustainability,and has been widely used.However,its water resistance and corrosion resistance still have some shortcomings,which limit its practical application.In this paper,phytic acid-doped melamine(PA-AT)and melamine phosphate(MP)functionalized graphene oxide were prepared respectively,and the functionalized modified graphene oxide was used as a filler to add to the waterborne polyurethane coating.The electrochemical properties and mechanical properties of the coating were studied,and its anticorrosion mechanism was also discussed.The main contents and conclusions of this paper was as follows:1.GO/PA-AT was prepared by non-covalent functional modification of graphene oxide(GO)with phytic acid-doped trianiline(PA-AT),and GO/PA-AT was added to waterborne polyurethane as filler to prepare functionalized graphene oxide waterborne composite coating(GO/PA-AT/WPU).The structure of the complex was characterized by spectroscopy,scanning electron microscopy,and thermogravimetry.The corrosion resistance of GO/PA-AT waterborne composite coatings was investigated by neutral salt spray experiments and electrochemical impedance spectroscopy(EIS).And adhesion,hardness and impact resistance tests were used to explore the mechanical properties of GO/PA-AT waterborne composite coatings.At the same time,the contact angle test of the composite coatings was carried out.The results showed that when the mass ratio of GO to PA-AT in the GO/PA-AT composite was 1:3 and the addition amount of GO/PA-AT was 0.8 g,the corrosion resistance efficiency of the composite coatings was 99.90%.The adhesion of the coating was3.57 MPa,and the sample after 168 h of salt spray test was tested for adhesion,and the loss was 38%.The GO/PA-AT/WPU coating had a film hardness of 4H and an impact strength of 50 cm and above.The results of the contact angle test showed that the addition of GO/PA-AT made the pure WPU coating increase from 77.3°±1° to105.4°±0.8°.The anticorrosion mechanism is that synergistic effect of the barrier mechanism of GO,the passivation mechanism of AT and the chelation mechanism of PA,the water-borne composite coatings provide limited protection.2.GO/MP was prepared by covalently functionalizing GO with melamine phosphate(MP).GO/MP was added to waterborne polyurethane to prepare a functionalized graphene oxide water-borne composite coating(GO/MP/WPU).The structure of the complex was characterized by spectroscopy,scanning electron microscopy,and thermogravimetry.The corrosion resistance of GO/MP waterborne composite coatings was investigated by neutral salt spray experiments and electrochemical impedance spectroscopy(EIS).And adhesion,hardness and impact resistance tests of composite coatings were used to explore the mechanical properties of GO/MP waterborne composite coatings.At the same time,the contact angle test of the composite coatings was carried out.The results showed that when the mass ratio of GO to MP in the GO/MP composite was 1:3 and the addition amount of GO/MP was 0.8 g,the corrosion resistance efficiency of the GO/MP composite coating was99.78%.The adhesion of the coating was 4.09 MPa,and the sample after 168 h of salt spray test was tested for adhesion,the loss was 49%.The GO/MP/WPU coating had a film hardness of 5H and an impact strength of 50 cm and above.The results of the contact angle test showed that the addition of GO/MP made the coating of pure WPU rise from 77.3°±1° to 99.8°±0.6°.The anticorrosion mechanism is that synergistic effect of GO barrier mechanism,good dispersion of GO/MP and enhanced mechanical strength provides effective protection for the waterborne composite coatings.