Preparation Of GO-PANI Nanosheets And Study On Corrosion Resistance Of Composite Coatings

At present,organic coatings are one of the most commonly used and cost-effective anticorrosion means,but the molecular structure of its polymer film-forming material itself,the semi-permeability,and internal defects of the formed film make the organic coatings inevitably fail due to external mechanical damage,corrosion medium penetration and chemical erosion during service.Previous studies have shown that the dispersion of graphene oxide(go)nanosheets into the organic coating can form a "zigzag path" and effectively delay the corrosive medium from reaching the metal substrate surface,so as to improve the permeability of the coating.On the other hand,conductive polymer polyaniline(PANI)has unique active metal corrosion resistance characteristics,and its action mechanism does not depend on solubility.Therefore,PANI as an active pigment will not cause the deterioration of the barrier effect of the coating.Therefore,the construction of GO-PANI nanosheet is expected to give full play to the respective advantages of GO nanosheet and PANI to obtain pigment with both physical barrier and active properties.The main contents and research ideas of this paper include:(1)GO-PANI nanosheets with good dispersion and stability were synthesized by ultrasonic chemical method;(2)Preparation of epoxy composite coating(GO-PANI-ER)by direct and uniform dispersion of GO-PANI nanosheets and GO-PANI nanosheets orderly layered coating and GOPANI-AR orderly layered coating by electrophoretic deposition of GO-PANI nanosheets without and with polyacrylic acid resin;(3)Investigating the corrosion electrochemical behavior of GO-PANI-ER coating,GO-PANI coating,and GO-PANI-AR coating in 3.5wt.% Na Cl solution.The results showed that:(1)The experimental results show that when the mass ratio of go to PANI is 2:1,namely GO-PANI-2-1 prepared by the ultrasonic chemical method has good dispersion and stability.SEM and TEM show that GO-PANI-2-1 retains the nanosheet structure of GO,while UV Vis,FT-IR,and XPS show that PANI is successfully grafted onto the surface of GO nanosheet;(2)The electrochemical test results of the composite coating with a pigment content of 1 wt.% show that the self-corrosion potential of GO-PANI-ER coating(-0.57 V)is significantly higher than that of PANI-ER coating(-0.62 V)and GO-ER coating(-0.58 V),and its impedance modulus is the largest in the low-frequency region,that is,GO-PANI-2-1 as an antirust pigment has better performance than GO nanosheet and PANI.The reason may be that GO-PANI-2-1 has both the advantages of GO nanosheet and PANI;(3)The GO-PANI coating with an orderly layered structure was successfully obtained by electrophoretic deposition of GOPANI nanosheets.However,after immersing in 3.5 wt.% Na Cl solution for 96 hours,the GO-PANI coating peeled off and broke.The reason is that PANI itself is a rigid polymer,which makes the GO-PANI coating brittle and easy to be damaged;(4)GO-PANI-AR coating with an orderly layered structure was successfully obtained by electrophoretic deposition by mixing GO-PANI nanosheet and polyacrylic acid resin(AR).Compared with AR coating,GO-AR coating,and GO-PANI-AR composite coating,GO-PANI-AR coating can provide a better corrosion protection for carbon steel substrate,which is attributed to the dual antirust characteristics of GO-PANI-2-1 and the structural advantages of orderly layered distribution of nanosheets.