Preparation Of Polyaniline Doped With Different Acids And Study On The Anticorrosion Performance Of Its Composite Epoxy Coating

Metal materials have good mechanical properties,which make them play an important role in various fields.Metal corrosion not only affects the reliability of infrastructure and industrial facilities,but also induces major safety accidents and endangers social security.Polyaniline has the advantages of simple preparation process,cheap raw materials,stable properties,etc.It is the most studied conductive polymer in the field of anticorrosion.However,Polyaniline molecular chain is a typical rigid structure,and its application is limited by its insolubility.In order to improve the anti-corrosion performance of Polyaniline and its dispersion stability in the epoxy coating system,two kinds of Polyaniline doped with acid were designed and synthesized,and their structures were characterized.The anti-corrosion performance of the composite epoxy containing acid doped Polyaniline coatings was studied.(1)Firstly,Hydroxyphosphono-acetic acid doped Polyaniline(HPA-PANI)was successfully synthesized by oxidative polymerization.XPS?SEM?UV-vis?FI-IR?XRD?Raman were used to characterize the chemical structures and morphologies of HPA-PANI.The characterization results show that the average diameter of HPA-PANI anofibers is approximate 50 nm.The anticorrosive properties of HPA-PANI/epoxy composite coatings on low carbon steel were investigated.After immersion in 3.5 wt%Na Cl solution for 30 days,the corrosion layers of the coatings were characterized by using SEM-EDS and XPS.Moreever,we propose a plausible model to describe the anti-corrosion mechanism of HPA-PANI,and analyze the role of doped ions(HPA)in the corrosion process.The results show that due to the passivation ability of HPA-PANI and the corrosion inhibition ability of doped acid,the anticorrosion performance of the composite coatings is significantly better than that of the pure epoxy coating.The protective performance of the epoxy coating with the HPA-PANI content of 1 wt%is the best,and the impedance remains 4.18×10~7?/cm~2after immersion.(2)Self doped sulfonated polyaniline(SPANI)was prepared from aniline and 2-aminobenzenesulfonic acid by rapid oxidative polymerization.XPS?SEM?FI-IR were used to characterize the chemical structures and morphologies of SPANI.The waterborne epoxy coatings with different SPANI contents(0.5wt%,1 wt%,2 wt%)were prepared by adding SPANI into the waterborne epoxy resin,and the anticorrosive properties of SPANI coatings were studied.Compared with pure waterborn epoxy coating,the protective performance of SPANI coating was significantly improved,and 0.5 wt%SPANI coating presented the best protection.In addition,the SPANI/ATO composite and the SPANI/ATO coatings also were prepared.By comparing the polarization curves,EIS and equivalent circuit fitting results of different coatings,the influence of the inorganic compound(ATO)on the properties of SPANI epoxy coating was explored.After immersion in Na Cl solution for 15 days,the impedance value of SPANI/ATO coating is 1-2 orders of magnitude higher than that of SPANI coating and pure epoxy coating.The EIS results show that SPANI/ATO can effectively enhance the barrier effect of waterborne epoxy coating.