| Anticorrosive coatings can protect metal substrates and prevent corrosion.Waterborne anticorrosive coatings have become the focus of anticorrosive coatings research because of their advantages of environmental protection and low VOC emission.Due to the excellent structure and properties of graphene oxide and polyaniline/graphene oxide,waterborne epoxy zinc-rich coatings were modified to prepare waterborne epoxy zinc-rich coatings with excellent corrosion resistance(reducing the content of zinc powder),realizing the purpose of environmental protection,resource saving and production cost reduction.The research work of this paper consists of two parts:Part I: Preparation of graphene(GO)/waterborne epoxy zinc-rich coatings.Five GO with different oxidation degrees were prepared by changing the dosage of oxidizing agent using the improved Hummers,which were GO-1,GO-2,GO-3,GO-4 and GO-5.Then,Fourier Transform Infrared Spectrometer(FTIR),X-ray Photoelectron Spectroscopy(XPS)and X-ray Diffraction(XRD)were used to characterize the five GO.In order to explore the effect of oxidation degree of GO on coating corrosion resistance,five GO-modified waterborne epoxy zinc-rich coatings were prepared,and the mechanical,electrochemical and salt spray resistance properties of the coatings were tested.The results show that the GO-3 system has the best comprehensive performance.Next,the effects of GO-3 and zinc powder content on the coating were investigated through mechanics,electrochemistry and salt spray resistance.The experimental results show that: The coating prepared by GO-3 prepared with 2g graphite and 5g potassium permanganate has better corrosion resistance.When the GO-3 content is 0.3% and the zinc powder content is 70%,the coating hardness is 4H,the flexibility is 2mm,the impact strength is 50kg/cm,and the adhesion grade is 0.The impedance values of the coatings soaked in 3.5%Na Cl solution for 4h,72 h,240h and720 h respectively reached the maximum and the salt spray resistance time reaches1272 h.GO-3 can replace 10% zinc powder in original epoxy zinc-rich coating(80%zinc powder,same below),and its salt spray resistance time is 1.36 times that of original epoxy zinc-rich coating.Part II: Preparation of polyaniline/graphene oxide(PAGO)waterborne epoxy zinc-rich coatings.Five kinds of PAGO composites were prepared by in-situ polymerization of aniline and GO with different oxidation degrees(GO-1-GO-5),which were labeled as PAGO-1,PAGO-2,PAGO-3,PAGO-4 and PAGO-5,respectively.And polyaniline was prepared under the same conditions as the control group.In order to explore the effect of the oxidation degree of GO on the anticorrosion performance of the PAGO material,five kinds of PAGO were used to modify waterborne epoxy zinc-rich coatings,and the mechanical,electrochemical and salt spray resistance properties of the coatings were tested.By changing the compound ratio of GO to aniline(1%-4%),four kinds of PAGO with different compound ratio were prepared and labeled as PAGO-3-1,PAGO-3-2,PAGO-3-3 and PAGO-3-4,respectively.The effects of composite ratio of PAGO on PAGO/waterborne epoxy zinc-rich coatings were investigated by testing the properties of mechanics,electrochemistry and salt spray resistance.The results show that the PAGO-3 system has the best comprehensive performance.Finally,the influence of content of PAGO-3-3 and zinc powder on mechanical,electrochemical and salt spray resistance of PAGO/water-based epoxy zinc-rich coating was further investigated.The experimental results show that: When GO-3 was used as composite material and the composite ratio of GO-3 and aniline was 3%,the prepared PAGO-3-3 coating had better corrosion resistance.When the content of PAGO-3-3 is 0.2% and the content of zinc powder is 80%,the hardness of the coating is 4H,the flexibility is 2mm,the impact strength is 50kg/cm,and the adhesion grade is 0.The impedance values of the coatings soaked in 3.5%Na Cl solution for 4h,72 h,240h and 720 h respectively reached the maximum.And the salt spray resistance time up to 1464 h,which can reach atmospheric corrosion level C4～C5according to the standard HG/T 5573-2019 "Graphene Zinc Powder Coating",and is1.56 times that of the original epoxy zinc rich coating.In addition,When the content of PAGO-3-3 is 0.2% and the content of zinc powder is 60%,the hardness of the coating is 3H,the flexibility is 3mm,the impact strength is 45kg/cm,and the adhesion level is0.The impedance of the coating soaked in 3.5%Na Cl solution for 4h,72 h,240h and720 h respectively is close to that of the original epoxy zinc-rich coating.And the salt spray resistance time up to 960 h,which means that PAGO-3-3 can achieve corrosion performance close to the original epoxy zinc-rich coating,while replacing 20% of the zinc powder in the original epoxy zinc-rich coating. |
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