| With the rapid expansion of the marine strategy,China has built a large number of port constructions,ship bridges and deep sea exploration with steels,and they are served in harsh marine corrosive environments for long-term.This phenomenon has caused nearly one trillion yuan of economic losses,which will greatly hinder people's pace to explore the ocean.At present,epoxy coating is one of the most common and effective measures for anti-corrosion of steels.However,conventional epoxy coatings have some drawbacks in performance and application that are difficult to meet the demanding service environment and higher usage requirements.Graphene is considered to be an ideal material for improving the corrosion resistance of epoxy coatings due to its high specific surface area and good chemical stability.Graphene mainly plays the role in physical shielding and inhibition of microscopic defects in coatings.However,corrosion protection and failure of coatings is a long-term,dynamic and complex process.The intrinsic structure,size and distribution state of graphene have important influences on the anti-corrosion behaviors,which requires further in-depth research.Based on the main functions of graphene in the interior of the composite coating,the corrosion resistance of graphene epoxy composite coating was studied.The main research contents and conclusions are as follows:1.Four different graphene were employed to prepare the waterborne epoxy resin composite coatings.The effects of the size of graphene on the corrosion behavior of the composite coating in3.5 wt%NaCl solution were systematically investigated.The results show that the EP-G_a composite coating occupied the optimal protection performance.EP-G_a composite coating has the largest low-frequency impedance modulus among the coatings,and the value of the first day is1.22×10~8?·cm~2.After 32 days of immersion,the value still maintains 10~6?·cm~2,reflecting good long-term corrosion resistance ability.This is mainly attributed to the graphene sheet with complete lamellar structure which can exert a better the physical shielding role,effectively inhibiting the infiltration,penetration and diffusion of the corrosive medium,and then improving the anti-corrosion performance of the composite coating.2.Low conductivity(0.01 S/cm)GO and high-conductivity(10 S/cm)rGO were prepared by Hummers method and reduction reaction,and related epoxy zinc-rich composite coating was prepared.The corrosion behaviors of the composite coatings were systematically investigated.The results show that the ZRE-rGO composite coating has the optimal anti-corrosion capability.ZRE-rGO composite coating has the largest low-frequency impedance modulus,and the value of the first day is up to 2.85×10~8?·cm~2.After 57 days immersion.This is mainly attributed to in the zinc-rich system,the highly conductive rGO not only acts as a physical shield,but also activates the zinc particles.The function fully activates the zinc particles and increases the utilization rate of the zinc powder,thereby prolonging the cathodic protection time of the coating and improving the service life of the composite coating.3.The corrosion-promoting activity of graphene was inhibited by fluorine-doped rGO.The composite coating of fluorine-doped reduced graphene oxide/waterborne epoxy resin was prepared.The corrosion protection performance of the composite coating was investigated by electrochemical techniques.The results show that the fluorine-doped reduced graphene oxide modified epoxy composite coating has the highest low-frequency impedance modulus(6.54×10~8?·cm~2),and its value is still stable at 10~7?·cm~2 after 40 days immersion,suggesting the best corrosion protection performance.This is mainly due to F can effectively suppress the corrosion-promoting activity of highly conductive rGO,and at the same time,it can fully exert the inhibition of microscopic defects and physical shielding role of graphene by ionic liquid modification. |
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