| Polyaniline(PANI)was widely used in the metal anticorrosion field for its excellent electrical conductivity,unique doping-dedoping process,special pitting resistance and superior stability in differnent environment.This paper aimed to introduce the preparation of high-performance polyaniline anticorrosive coating.The paper started from the preparation of polyaniline nanofibers by direct mix reaction method in perchloric acid systems.The effects of different reaction conditions on the properties of perchloric acid doped polyaniline in perchloric acid system were investigated.After the perchloric acid doped polyaniline was dedoped by ammonia,taked the secondary dope by perchloric acid,oxalic acid,molybdic acid and tannic acid,to get secondary doped polyaniline nanofibers.The products were analyzed by scanning electron microscopy(SEM),four-probe conductivity tester,infrared spectroscopy tester(IR)and ultraviolet spectroscopy tester(Uv-vis).The anticorrosion property of different polyaniline-epoxy blends coating was tested through electrochemical workstation.At last,the effects of polyaniline,pigment,additives on the basic physical properties of coatings and anticorrosion property were explored in this paper.The main results are as follows:(1).In direct mixed oxidation polymerization,the optimum reaction conditions of synthesising perchloric acid doped polyaniline were as follows: the molar ratio of aniline ammonium persulfate was 0.8:1,the temperature was 20 oC,the acid concentration was 1 mol/L,and the time was 24 h.Under such conditions,the polyaniline product obtains the best fiber morphology.The diameter of nanofibers was between 100-120 nm and it’s length was more than 600 nm.The fiber products are crossed and form a network structure.When the products of polyaniline gain the best morphology,the productivity,conductivity and anticorrosion efficiency would be the highest.It’s productivity could reach up to 110.11%,the conductivity could reach 0.2 S/cm,which indicated that the morphology of the polyaniline had an important effect on the properties of the polyaniline products.The study has laid a good foundation for the research on secondary doped polyaniline materials.(2).The fibers length of the secondary doped with polyaniline were slightly increased than the first doped polyaniline and the intrinsic polyaniline fibers.The thickness was uniform and the morphology was good.The UV spectra of the polyaniline showed that the secondary doped acid can effectively doped into the intrinsic molecular structure of the polyaniline.The results of AC impedance test showed that the anti-corrosion acid secondary doped polyaniline has better anti-corrosion properties than perchloric acid doped polyaniline on Q235 B carbon steel,and different secondary doped acid have quite different anti-corrosion properties.When the coating was soaked in the 3.5wt.% NaCl for 120 days,the impedance of the perchloric acid doped polyaniline coating was 4.21×106 Ω·cm2,while the impedance of tannic acid and oxalic acid secondary doped polyaniline coating was larger,keeping in more than 109 Ω·cm2.The impedance of the secondary doped polyaniline coating was the highest,which was 1.34×109 Ω·cm2.(3).The content of polyaniline,pigment and auxiliary agent can influence the adhesion of coating.With the increase of the amount of coating,the coating adhesion was increased first and then decreased.Through the electrochemical impedance test and salt spray test,the author found that polyaniline-epoxy resin coating has excellent anticorrosion property on the Q235 B carbon steel,and the different content of components has a great influence on anti-corrosion properties.After soaking for 120 days,the optimum coating resistance remains 7.14×109 Ω·cm2,and the salt spray test results also confirmed that it has a good corrosion resistance.Considering the above factors,the optimal formulation of polyaniline-epoxy resin coating is: 1wt.% of oxalic acid doped with polyaniline,10 wt.% of zinc phosphate,3wt.% of the auxiliary agent,others are epoxy resin. |
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