Research On Amino Modified Graphene Oxide Novel Composite Coatings And Their Anticorrosion Performance

Coating protection technology has received widespread attention in the field of metal corrosion and protection due to its short R&D cycle,low cost and strong operability.However,traditional coatings are prone to various defects during the protection process,which leads to the failure of the coating by causing the directly contact of metal substrate and corrosive medium.Due to its larger specific surface area and excellent shielding effect,graphene oxide（GO）is often used as a filler in the development of new anticorrosion coatings.However,in practical applications,GO often agglomerates and accumulates due to the van der Waals forces between its layers and thus cannot exert its excellent barrier properties.Therefore,in this paper,amino-modified graphene oxide（FGO）was prepared by using three low-cost and non-toxic ammoniates,including aniline trimer,2-6diaminopyridine and semicarbazide,as modifiers to improve the dispersion of GO and obtain high corrosion resistance composite coating.The effects of modification reaction temperature and the proportion of modifier on the preparation and anticorrosion performance of FGO were analyzed.Then FGO was added to the epoxy coating（EP）to prepare amino-modified graphene oxide composite coatings（FGO/EP）.The influence of the addition amount of FGO and the type of modifier on the anticorrosion effect of FGO/EP was investigated and the anticorrosion mechanism of the graphene oxide novel composite coatings was revealed.The results are as follows:The effects of modification reaction temperature and the proportion of modifier on the anticorrosion performance of FGO composites were analyzed systematically.GO was modified at different reaction temperatures to prepare composites,including semicarbazide modified graphene oxide（NGO）,2-6 diaminopyridine modified graphene oxide（BGO）and aniline trimer modified graphene oxide（ATGO）.XRD,Raman and FT-IR were used to characterize the phase structure.It was determined that NGO,BGO and ATGO composites were successfully prepared.And it is concluded that the optimal reaction temperatures for the preparation of three composites were 95℃,80℃and 95℃,respectively.After modification,the layer spacing and internal disorder of GO were improved,and a new characteristic peak C-N bond was formed,which proved that amino modifiers were successfully grafted onto the GO.SEM,AFM and TEM were used to observe the surface morphology of three kinds of FGO before and after modification.The single-layer sheet structure of GO had no change,and the dispersity and roughness of GO were obviously improved.That made it possible for FGO to form a barrier shield in the coating.Similarly,three kinds of FGO composites were prepared by different ratios of modifier and GO at the optimum modification temperature.Their phase structures were characterized by XRD,Raman and FT-IR.The results showed that GO have the best modification degree when the ratio of the modifiers and GO are 1:5.The influence of the addition amount of FGO on the anticorrosion performance of FGO/EP composite coatings was analyzed systematically.The semicarbazide modified graphene oxide composite coatings（NGO/EP）,2-6 diaminopyridine-modified graphene oxide composite coatings（BGO/EP）and aniline trimer modified graphene oxide composite coatings（ATGO/EP）were prepared according to the different addition amounts of FGO.Electrochemical test,salt spray test and adhesion test were used to analyze the anticorrosion performance of the composite coatings.The results showed that the anticorrosion performance of the composite coatings increased firstly and then decreased with the increase of FGO content,and reached the best anticorrosion performance at 0.1wt.%,0.1 wt.%and 0.05 wt.%addition amount respectively.At these addition amount,the|Z|_0.01Hz impedance modulus of the composite coatings reached the highest value.Their coating resistance increased from 3.89×10⁴Ωof EP to 4.22×10⁷Ω,2.75×10⁹Ωand6.87×10⁶Ωrespectively.Their polarization resistance increased from 6.82×10⁶Ωof EP to1.30×10⁹Ω,1.35×10¹⁰Ωand 5.60×10⁸Ωrespectively.After 300 h of salt spray test,the corrosion morphology of Q235 steel plates coated with three kinds of composite coatings were mainly the corrosion expansion near the scratch,and the distribution of corrosion spots were less than other coatings.There was no sharp decreases in dry adhesion of coatings adding FGO,and the composite coatings showed higher wet adhesion and lower adhesion loss.The wet adhesion of the composite coatings increased from 0.50 MPa of EP to 1.90 MPa,1.89 MPa and 0.82 MPa.The adhesion loss of the composite coatings decreased from 81%of EP to 18%,7%and 67%,respectively.These performance guaranteed the advantages of coatings’anticorrosion ability.The anticorrosion performance and anticorrosion mechanism of amino-modified GO composite coatings were revealed.The anticorrosion performance of three kinds of composite coatings 0.1%NGO/EP,0.1%BGO/EP and 0.05%ATGO/EP under the optimal FGO addition were compared.The results showed that 0.1%BGO/EP composite coating has higher|Z|_0.01Hz impedance modulus,larger capacitance arc and smaller corrosion current.Compared with 0.1%NGO/EP and 0.05%ATGO/EP,its coating resistance was increased by 2 and 3 orders of magnitude,and its polarization resistance was increased by1 and 2 orders of magnitude,respectively.At the same time,the 0.1%BGO/EP composite coating shows strong salt spray corrosion resistance and adhesion performance.The analysis and calculation of the plane-strain analytical model of the composite coating also showed that 0.1%BGO/EP composite coating has the best theoretical adhesion,which is consistent with the conclusion of the adhesion test.In conclusion,the anticorrosion mechanisms of amino modifier in improving the dispersion,adhesion of GO and the formation of passivation film of metal matrix are further revealed from the perspective of synergism between modifier&GO and molecular dynamics,which provides a theoretical basis and technical support for the application of FGO/EP composite coating in the fields of corrosion and protection.