Study On Preparation Of Graphene Oxide Modified Waterborne Epoxy Zinc-Rich Coatings And Their Performance

Water-borne epoxy zinc-rich coatings have no volatile organic compounds and no harm to the natural environment,which is an important trend in the future development of coatings.However,compared with solvent-based zinc-rich anti-corrosion coatings,their anti-corrosion performance needs to be improved.Graphene oxide has large specific surface area and barrier and shielding properties of sheet structure,so it has great application potential in waterborne epoxy zinc-rich anticorrosive coatings.At the same time,the large surface energy of graphene oxide makes it easy to agglomerate in waterborne epoxy zinc-rich anticorrosive coatings.Based on this,this paper takes waterborne epoxy zinc-rich coating as the research object,through grafting GO with L-tryptophan and grafting GO with L-lysine,the modified graphene oxide was added into the coating system,and the effects of its addition amount on the mechanical properties and corrosion resistance of waterborne epoxy zinc-rich coating were studied respectively.The main research results are as follows.(1)Covalently grafting graphene oxide(GO)by L-tryptophan(L-Trp)to obtain L-tryptophan grafted graphene oxide(L-Trp-GO),and preparing L-Trp-GO/Water-based epoxy zinc-rich coating.The results of infrared spectroscopy and X-ray photoelectron spectroscopy show that the amino group of L-Trp forms-CO-NH-bond and C-N bond with the carboxyl group and epoxy group of GO respectively.The results of Raman spectroscopy show that the ID/IG of graphene oxide is 0.9,and the ID/IG of GO grafted by L-TRP is 0.93;The results of atomic force microscope and scanning electron microscope show that the thickness of GO is 0.93 nm,and the thickness of L-Trp-GO after grafting is about 1.3 nm,and the surface wrinkles of graphene oxide after grafting increase.(2)When the amount of L-Trp/GO in waterborne epoxy zinc-rich coating increases gradually,the hardness of the coating remains unchanged for 5H.However,the adhesion of the coating increases first and then decreases.When the content of L-Trp/GO is 0%,0.4%and 0.6%,the adhesion of the coating is grade 1,and when the content of L-Trp/GO is 0.2%,the adhesion of the coating is grade 0.The impact resistance of the coating increases at first and then remains unchanged.When the content of L-Trp/GO is 0,the impact strength of the coating is less than 50 kgcm-1,and after adding L-Trp/GO,the impact strength of the coating is 50 kg·cm-1 and remains unchanged.Electrochemical impedance spectroscopy and Tafel polarization curve experiments show that the corrosion resistance of waterborne epoxy zinc-rich coating increases first and then decreases with the increase of L-Trp/GO content.when the L-Trp/GO content in the coating is 0.2%,the best corrosion resistance of the coating is the best.(3)Graphene oxide(GO)was grafted with L-Lysine(L-Ly)to obtain L-Lysine grafted graphene oxide(L-Ly-GO),and preparing L-Ly-GO/Water-based epoxy zinc-rich coating.The results of FTIR and XPS showed that the amino group of L-Trp was different from the carboxyl group and epoxy group of GO respectively.The results of Raman spectroscopy show that the IG/IG of GO grafted by L-Ly is 0.95;The results of atomic force microscope and scanning electron microscope show that the thickness of GO is about 0.93 nm and that of L-Ly-GO is about 2.83 nm.A fter grafting,the surface wrinkles of graphene oxide increase.(4)With the increase of L-Ly/GO content,the hardness of the obtained L-Ly-GO/waterborne epoxy zinc-rich coating first increases and then remains unchanged.when L-Ly/GO content is 0,the hardness of the coating is 5H,and when L-Ly/GO is added,the hardness of the coating is 6h.The adhesion of the coating remains unchanged after increasing.The adhesion of the coating is grade 1 when L-Ly/GO content is 0%,and grade 0 when L-Ly/GO content is 0.2%,0.4%and 0.6%.Impact resistance of the coating increases first and then does not decrease.when L-Ly/GO content is 0%,0.4%and 0.6%,the impact strength of the coating is less than 50kgcm-1,and when L-Ly/GO content is 0.2%,the impact strength of the coating is equal to 50kgcm-1.Electrochemical impedance spectroscopy and Tafel polarization curve test show that the corrosion resistance of waterborne epoxy zinc-rich coating increases first and then decreases with the increase of L-Ly/GO content.when the L-Trp/GO content in the coating is 0.2%,the corrosion resistance of the coating is the best.(5)By comparing mechanical properties and corrosion properties of L-Trp/GO water-based epoxy zinc-rich coating and L-Ly/GO water-based epoxy zinc-rich coating,it can be concluded that when L-Trp/GO and L-Ly/GO are rich in water-based epoxy When the amount of zinc coating added is 0.2%,the resistance of the L-Trp/GO water-based epoxy zinc-rich coating is higher than that of the L-Ly/GO when the hardness,adhesion and impact resistance of the two coatings are about the same.The epoxy zinc-rich coating is close to an order of magnitude higher.This is because L-Trp/GO plays a shielding and blocking role in the coating.On the other hand,L-Trp is used as a corrosion inhibitor,L-Trp/GO Will be adsorbed on the surface of the metal substrate,thereby increasing the corrosion resistance of the coating.