Preparation And Anticorrosion Of Polypyrrole Composite Coating On Aviation Aluminum Alloy

2024 aviation aluminum alloy belongs to medium strength structural material,light weight,good ductility,widely used in aircraft skin,web,partition frame structure.However,the corrosion resistance of aviation aluminum alloy is not good,which is sensitive to intergranular corrosion and pitting corrosion affecting the safety and economy of aircraft.Based on the above situation,the surface corrosion treatment of aluminum alloy is particularly important.Polypyrrole（PPy）is a kind of conductive polymer material,which is environmentally and friendly and easy prepared.In recent years,it has attracted much attention in the field of anticorrosion.The PPy coating obtained by electrodeposition of pyrrole monomer acid solution on the surface of aluminum sheet shows good physical isolation performance.The inner structure and surface morphology of PPy coating obtained by electrodeposition have defects,which restrict its anticorrosion.In this paper,the preparation process of PPy coating is firstly studied,and then the influence of internal structure and surface morphology optimization about the anticorrosion performance of the coating is studied.Scanning electronic microscopy（SEM）is used to observe the surface morphology of the coating,and x-ray photoelecgon spectroscopy（XPS）,x-ray energy dispersive spectral analysis（EDS）,raman spectroscopy（Ramam）and fourier transform infrared spectrometer（FTIR）are used to analyze the structure and composition of the coating,and immersion experiment and polarization curve and electrochemical impedance spectroscopy are used to analyze the corrosion resistance of the coating.Those experimental results show that the optimum process conditions for electrodeposition of 0.4 mol/l pyrrole monomer and0.5 mol/l sulfuric acid solution on the electrochemical workstation is 0.65 V Plating voltage and 10 minutes electroplating time,and pH value of the electroplating solution is 1.PPy-MoO4^2-coating is prepared by doping sodium molybdenate into the coating to fill the defects such as voidage and pinhole in the inner structure of the coating.Mo element is in the form of MoO4^2-and MoO₃ filling the inner defects of the coating to prevent the diffusion of corrosion ions in the coating.PPy/rGO coating is prepared by electroplating rGO coating on the surface of PPy coating to remed the rough surface morphology,pinholes,grooves and other defects.Hydrogen bond is formed between rGO and PPy.rGO coating is made by rGO two-dimensional layered structure compact accumulation,and the surface of the coating is smooth,flat,showing good physical isolation performance.At the same time,PPy coating is doped with sodium molybdate,and rGO coating is electroplated on the surface to prepare PPy-MoO4^2-/rGO coating.The hydrophobic and anticorrosive properties of PPy,PPy-MoO₄^2-,PPy/rGO and PPy-MoO₄^2-/rGO coatings are compared.The maximum contact of PPy-MoO4^2-/rGO coating indicates the best hydrophobic property,and the maximum corrosion potential indicates the lowest corrosion tendency,and the minimum corrosion current density indicates the lowest corrosion rate.The electrochemical impedance spectra of the four kinds of coatings all are in the pitting corrosion induction period.The maximum capacitive arc resistance of PPy-MoO4^2-/rGO coating indicates that the resistance to corrosion ion is the strongest,and the maximum charge transfer resistance of Rct indicates that the charge transfers slowly in the coating,and the corrosion rate is slow.The four kinds of coatings show different degrees of corrosion after being immersed in 3.5%NaCl solution for 168 hours,among which the PPy-MoO4^2-/rGO coating has the lightest corrosion showing the best anticorrosion.