| According to the Chinese Academy of Engineering’s research on China’s corrosion status and control strategies,the annual corrosion cost in China is about310 billion US dollars,accounting for 3.34%of China’s GDP.Statistics show that by using effective corrosion protection strategies,15%-35%of global corrosion costs can be saved.Among them,coating protection is the most widely used and effective anti-corrosion technology,and anti-corrosion coatings account for about66%of this field in our country.In order to control environmental pollution and protect the health of workers/users,China has formulated a series of measures to limit the use of high volatile organic compound（VOC）coatings.The amount of volatile compounds released by waterborne epoxy coatings is extremely low,making it the focus of the development of environmentally friendly anti-corrosion coatings.However,the structure of waterborne epoxy coatings is composed of hydrophilic groups and surfactants,causing corrosive ions to easily diffuse into these coatings,and waterborne coatings tend to form more defects and pores during the curing process,providing more diffusion paths for corrosive electrolyte.Waterborne epoxy coatings have been used commercially for 40 years,but their use in harsh environments has been limited due to their short service life.This paper innovatively designed and synthesized a series of two-dimensional novel graphene oxide-based hybrid nanomaterials.Based on the material’s maze effect and special inherent properties,point-sheet decoration,sheet-sheet stacking,sheet-sheet intercalation,and wrapped two-dimensional nanohybrid materials were constructed through covalent hybridization and functional modification.To improve the dispersion performance of 2D nanohybrid materials and prevent their agglomeration,they were functionalized with alkoxysilanes prior to being incorporated into a polymer matrix.By mixing 0.1 wt.%functionalized 2D nanohybrid material with a polymer coating using a solution mixing method,nanopolymer coatings of graphene oxide/carbon nitride（GO@CN）,graphene oxide/zinc oxide quantum dots（GO@Zn O QDs）,graphene oxide/MXene（GO@MXene）,and graphene oxide/metal-organic frameworks（GO@MOFs）were prepared,resulting in a significant improvement in the corrosion resistance of waterborne epoxy coatings.The structures and morphology of these nanomaterials,as well as the chemical interactions between silane reagents and nanofillers were investigated by various characterization means such as XRD,FT-IR,TEM,and XPS.The results of water contact angle,pull-off adhesion,fracture-area observation,EIS and salt spray test of the prepared coating system proved that the nanocomposite material have a significant improvement in corrosion resistance compared with pure epoxy coating;while,the nanocomposite coating has more comprehensive anti-corrosion performance and chemical stability when soaked in 3.5 wt.%Na Cl solution.After loading the nanohybrids in the polymer matrix,the corrosion spots and blistering around the scratches were significantly reduced.According to the SEM image of the fracture area,the nanohybrids can be uniformly distributed in the coating matrix.It can be seen that the nanohybrids play an important role in preventing the path of corrosive ions and increasing the compactness of the epoxy resin matrix.Therefore,the highest corrosion resistance can be achieved by using nanocomposite coatings on steel substrates.And the verification of antibacterial performance and real sea antifouling performance of nanocomposite coatings containing MOFs and Zn O QDs also confirmed the application potential of its coating system in antifouling.The maze effect of nanocomposites enhances the barrier performance of the coating,and at the same time improves the mechanical properties of the coating.The hybrid synthesized nanomaterials endow the coating with multifunctional properties due to their inherent properties such as high volume ratio and sterilization.The 2D nanohybrid modification technology enables different nanomaterials to play their respective advantages in the same coating system,abandon their shortcomings,and prevent them from agglomerating in the coating with excellent comprehensive performance.The anticorrosion mechanism is mainly attributed to the following aspects:（1）The effect of nanofillers and silane groups,the surface roughness and water contact angle of nanocomposite coatings are higher than that of pure epoxy coating samples,and nanofillers change the surface morphology of polymers;（2）The nanocomposite coating has a high adhesion strength to the metal substrate,which is almost more than twice that of the pure epoxy coating,and the silane leads to the formation of strong Fe-O-Si covalent bonds,and the nanomaterials in the polymer matrix form a tight bond in the middle,increase the adhension strength;（3）Silane-modified nanomaterials can significantly improve the barrier properties of polymer coatings.EIS results confirmed that nanofillers can increase the Rporeand Rctvalues of coating and reduce the Qcand Qdlvalues.These nanofillers can block pores and increase the path for the corrosive agent to penetrate into the interface between the coating and the metal substrate.Taking advantage of the synergistic effect between organic-inorganic composite nanomaterials and aminosilanes,the possibility and importance of nanohybrids combining the advantages of different nanomaterials in one coating system and abandoning the disadvantages are confirmed.The developed graphene oxide-based heavy-duty anti-corrosion coating system solves the technical problems of easy peeling and poor durability of environmentally friendly waterborne epoxy coatings in harsh marine environments,and endows the same system with multi-functional application potential. |
