Anti-corrosion Performance Of Novel Epoxy Composite Coatings Filled With N-doped Carbon Nanodots

Metal corrosion is one of the important factors causing damage to equipment structure,which often leads to shutdown loss and even production accidents.In order to prevent or delay metal corrosion,coating protection is the most widely used.Epoxy resin is widely used in the field of coatings because of its excellent adhesion and chemical resistance.As a thermosetting resin,its high crosslinking degree makes the cured epoxy resin have high strength and rigidity.However,the high crosslinking degree of epoxy resin also makes the epoxy resin fragile and easy to crack,which restricts the anti-corrosion performance of epoxy resin.Improving the anti-corrosion performance of epoxy resin is the focus of current industrial production research.Nano materials play an important role in coating anti-corrosion modification because of their small size,high specific surface area and excellent functionality.Carbon nano dots are a new member newly introduced into the anti-corrosion field in recent years,and show excellent corrosion inhibition ability as corrosion inhibitor.Therefore,this paper will take the epoxy resin coating widely used in the market as the research object,explore the impact of adding carbon nano dots on the anti-corrosion performance of the coating,and analyze the anti-corrosion mechanism of the coating,so as to provide theoretical and technical support for improving the anti-corrosion performance of epoxy resin.In this paper,nitrogen-doped carbon nanodots(CNDs)were synthesized by a"bottom-up"technical route using a hydrothermal method using citric acid monohydrate as the carbon source and ethylenediamine as the nitrogen source.The microstructure and chemical structure of nitrogen doped carbon nanodots(CNDS)were studied and characterized by scanning electron microscope(SEM),transmission electron microscope(TEM),Fourier infrared spectrometer(FT-IR),ultraviolet visible spectrophotometer(UV VIS)and X-ray photoelectron spectroscopy(XPS).Using it as epoxy resin coating filler,a novel nitrogen-doped carbon nanodot solvent-based(CNDs/epoxy)epoxy composite coating and a new nitrogen-doped carbon nanodot waterborne epoxy(CNDs/EP)composite coating were prepared respectively.In terms of anti-corrosion performance,the water absorption of the a novel solven based epoxy composite coatings filled with N-doped carbon nanodots(CNDs/epoxy)and a novle waterborne epoxy composite coatings filled with N-doped carbon nanodots(CNDs/EP)were investigated by gravimetric method,respectively.The electrochemical workstation was used to study their corrosion resistance.The results show that the addition of CNDs can effectively change the water absorption and corrosion resistance of the coating.For the solvent-based epoxy composite coating,when the mass fraction of CNDs in the coating was 0.15wt.%,the water absorption of the coating was inhibitated,and the corrosion resistance was the best.After soaking at 3.5wt.%for 480hours,The low-frequency impedance of the coating remains at 1.85×10¹⁰ohm·cm~2,and the porosity of the coating is 6.23×10^-9cm^-2,It shows excellent corrosion resistance in sodium chloride solution.For waterborne epoxy composite coating,when the mass fraction of CNDs in the coating is 2wt.%,the water absorption of the coating is the lowest and the corrosion resistance is the best.After soaking in 3.5wt.%Na Cl solution for 240 hours,the low frequency impedance of the coating remains at 2.16×10~9ohm·cm~2,and the porosity of the coating is 2.31×10^-8cm^-2,indicating that 2wt.%CNDs/EP composite coating exhibits excellent resistance in 3.5wt.%Na Cl solution.In this paper,based on the characterization results of the coatings,a possible anti-corrosion mechanism of CNDs nanoparticles as fillers in epoxy coatings is proposed,that is,the addition of CNDs improves the barrier properties of coatings in the corrosive media,so that the layer can better resist the erosion of corrosive media.