Preparation And Anti-corrosion Performance Of Benzoxazine Composite Coatin

Metal has been widely used in various fields of human life due to its excellent conductivity,thermal conductivity and good processability.However,the corrosion of metal leads to the waste of non-renewable materials,which brings serious impact and irreversible damage to the world economy,environment and people’s life.Therefore,metal protection has become a hot topic at present.People take anti-corrosion measures for metals by using different protection methods,among which organic coating is a kind of anti-corrosion material with the best comprehensive performance and the easiest material.Organic coating can form a certain thickness of coating on the metal surface through physical,chemical or other ways,which can have Effectively separate the metal from the corrosive medium.It avoids the direct contact between the metal and the corrosive medium,thus protecting the metal.In recent years,benzoxazine is a kind of high-performance thermosetting resin which has been successfully industrialized.Compared with traditional thermosetting resin,benzoxazine has low surface free energy,zero shrinkage,good electrical insulation and flexible molecular design.These characteristics make benzoxazine as a corrosion-resistant material has a great prospect and important significance.In this paper,aiming at some defects of traditional organic coatings,such as poor adhesion to the substrate,poor mechanical properties and high cost,benzoxazine a-bisphenol is taken as the main body,and the advantages of benzoxazine are brought into full play.Firstly,considering the defects of PBa,such as high brittleness,poor mechanical properties and poor adhesion to the coating,the epoxy resin containing siloxane was introduced into the system,and the composite coating of Benzoxazine/siloxane containing epoxy resin(SiEPB)was prepared by physical blending and heat curing.The structure of the coating was analyzed by infrared spectrum.It was proved that benzoxazine reacts with epoxy resin before the formation of the coating,and the transition from Si-O-C bond to Si-O-Si bond was realized during the formation of the coating.The hydrophobicity of the composite coating was investigated by static contact angle test.The results show that the addition of epoxy resin containing siloxane can effectively improve the hydrophobicity of the coating(109 ± 1°),much better than MS(80 ± 1°)and PBa(96 ± 1°);the adhesion of SiEPB composite coating(grade 0)is significantly higher than PBA coating(Grade 5)by cross-sectional method and SEM;finally,the corrosion resistance of the coating is analyzed by electrochemical test,the results show that the corrosion rate of SiEPB composite coating(<3.17×10-5 mm/year)is significantly lower than MS sample(4.53×10-3 mm/year),At the same time,the protective efficiency of the composite coating is higher than 99%.Secondly,in order to improve the thermal stability and corrosion resistance of SiEPB composite coating,a series of SiEPB/SiO2 nanocomposite coatings with different SiO2 contents(1wt%,3wt%,5wt%)were prepared by thermal curing,which were modified by adding organic SiO2 nanoparticles on the basis of benzoxazine blended with siloxane epoxy resin.The results show that the organic modification makes the SiO2 nanoparticles connect with the siepb through covalent bond,which makes the nanoparticles disperse on the network structure and surface of the coating effectively,and improves the dispersion of the nanoparticles.SEM was used to investigate the morphology of the coating.The results showed that the higher the content of SiO2 nanoparticles,the more obvious the aggregation of the coating surface,the rougher the coating surface.Then,the electrochemical test method was used to measure the SiEPB/SiO2.The results show that the addition of SiO2 nanoparticles can effectively improve the corrosion resistance of the coating,and with the increase of the content,the corrosion resistance is more excellent.This is due to the attachment of SiO2 nanoparticles in the coating network structure and the formation of a dense network structure,which improves the compactness and shielding ability of the coating,and in gold When the amount of SiO2 is 5wt%,the performance of the coating is the best.The corrosion rate(1.05×10-6 mm/year)of the coating is 9 times lower than that of the siopb composite coating(9.59×10-6 mm/year)without nanoparticles,at the same time,the corrosion rate of MS low carbon steel sample(4.53×10-3 mm/year)was reduced by three orders of magnitude.Finally,the thermal stability of the composite coating was investigated by TGA.The results show that the addition of SiO2 nanoparticles can effectively improve the thermal stability of the coating,and the higher the content of nanoparticles,the better the thermal stability of the coating.Compared with the 45.7%residual rate of siepb at 800℃,the residual rate of SiEPB/5%SiO2 nanocomposite coating reached 54.4%.