Preparation Of PANI-inorganic Nanocomposites And Their Corrosion Resistance In Epoxy Coatings

Metal corrosion widely exists in daily life and industrial production,the direct economic and resource losses caused by corrosion are huge,and the surface organic anti-corrosion coating is the most widely used metal anti-corrosion method.Polyaniline（PANI）is an important conductive polymer with easy synthesis,it has the characteristics of easy availability of raw materials and relatively low cost.Polyaniline coating in the process of electrochemical corrosion can promote the formation of dense oxide film（Fe₂O₃）on the metal surface through the rapid loss of electrons between the reversible redox state to achieve chemical protection of the substrate,which has become a research hotspot in the field of anti-corrosion coatings.However,insufficient mechanical properties,poor dispersibility and solubility have limited its industrial use in the coatings field.Therefore,polyaniline were composited with inorganic functional nanomaterials to prepare polyaniline-titanium nitride（PANI-TiN）and polyaniline-zirconium phosphate（PANI-ZrP）organic-inorganic composites with good dispersibility.The effect of the"synergy"of the two compounds on the corrosion resistance and anti-corrosion mechanism were investigated.In this paper,we carried out the following research:（1）PANI and different mass ratios of PANI-TiN composites were synthesis by chemical oxidative polymerization.Scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FT-IR）,Raman spectroscopy（Raman）,X-ray electron spectroscopy（XPS）and4-point probes resistivity measurement system were used to characterize the chemical structures,surface morphologies and electrical conductivity of PANI-TiN composites.The results showed that titanium nitride was uniformly present on the surface of polyaniline,and the agglomeration of polyaniline was decreased while the conductivity of composites was enhanced.（2）Different sizes of disc-shapedα-zirconium phosphate（α-ZrP）were synthesis by hydrothermal method.Polyaniline-zirconium phosphate nanocomposites（PANI-ZrP）with different mass ratios were prepared by chemical oxidative polymerization.The chemistry,surface morphology and electrical conductivity of PANI-ZrP composites were characterized by SEM,FT-IR,X-ray diffraction spectroscopy（XRD）and 4-point probes resistivity measurement system.The results indicated thatα-ZrP has the largest aspect ratio and regular hexagon crystal structure when the concentration of phosphoric acid is 3 mol/L.In the FTIR spectrum,the position and intensity of the characteristic peaks of PANI-ZrP composites changed with the increase ofα-ZrP,demonstrating that PANI andα-ZrP was grafted successfully.When the mass ratio of aniline monomer toα-ZrP is 1:0.8,the grafting between the both is best,and the aniline monomer is uniformly polymerized on the surface ofα-zirconium phosphate,which effectively reduces the agglomeration and conductivity of PANI.（3）The electrochemical corrosion resistance performance of PANI-TiN and PANI-ZrP organic-inorganic composite epoxy coatings was tested by long-term electrochemical impedance spectroscopy（EIS）and polarisation curve（LSV）,corresponding equivalent circuits were established based on EIS data using ZsimpWin software and the effect of functional fillers on the corrosion resistance and the corrosion kinetics process of coatings were analyzed.The experimental results showed that when the mass ratio of aniline monomer to TiN and aniline monomer toα-ZrP is 1:0.2 and 1:0.8,respectively,the organic-inorganic composite coatings have the best corrosion resistance.relatively pure epoxy substrate,the impedance value were increased to 1-2 orders of magnitude.The corrosion protection mechanism of the composite coatings also were investigated by analyzing the chemical composition（XRD and XPS）of the rust layer.The"passivation effect"of highly dispersed PANI and the"maze effect"of inorganic nanomaterials together promote the improvement of corrosion resistance.