Effect Of Surface Modification By Electropolymerization On The Corrosion Behavior Of High Purity Aluminum Foils

The aluminum foil of the aluminum electrolytic capacitor is usually performed in a highly acidic medium.During the electrolytic etching process,the acid solution may cause dissolution of the aluminum foil during the hole corrosion process,so that the thickness of the aluminum foil is reduced,ie,the ratio of the aluminum foil is reduced.The surface area,but also reduces the strength of the corrosion of aluminum foil,is not conducive to improving the performance of the capacitor.In this paper,conductive polymer films were prepared by electropolymerization on the surface of aluminum foils,surface modification was carried out to optimize the surface state of high-purity aluminum foils,and the electropolymerized surface-modified aluminum foils were subjected to corrosion by a coupling method of a corrosion cell method and an electrode reaction,respectively.In order to improve the phenomenon of over etching on the surface of the corroded aluminum foil and promote the formation of the tunnel hole,the corrosion inhibition effect and corrosion inhibition mechanism of the electro-polymerization surface modification on the electrolytic corrosion behavior of the aluminum foil are studied.This article mainly analyzes by section metallographic analysis,scanning electron microscope analysis,infrared spectrum analysis,atomic force microscope analysis,electrochemical test methods(including polarization curve,open circuit potential-time curve,alternating current impedance spectroscopy),analysis of weight loss rate and thinning rate.Methods such as corrosion aluminum foil samples were analyzed and characterized.Some laws of spontaneous corrosion of aluminum foil in the corrosion cell method and electrode erosion method were obtained.The effect of electropolymerization surface modification process on the effect of high purity aluminum foil on the surface was explored.Compared with the electro-polymeric surface modification before and after the corrosion and the corrosive cell method under the condition of no external power supply,the spontaneous erosion and the spontaneous erosion of the electrode coupling method perform different erosion effects.The scanning rate determined by the steady state polarization curve was determined by the electrochemical test method.The effects of sodium nitrate concentration and electropolymerization surface modification on the polarization curve,open circuit potential,and alternating current impedance of the aluminum foil during electrochemical corrosion were studied.Electropolymerization of surface-modified high-purity aluminum foils was similarly affected by spontaneous erosion of the etching cell method and spontaneous erosion by the electrode coupling method.The experimental results show that the surface modification of high-purity aluminum foil after electropolymerization alleviates the phenomenon of corrosion and shedding on the surface of corroded foil,resulting in the phenomenon of hole collapse and reduction in the rate of thinning,and it also promotes the growth of the tunnel hole to a certain extent.The specific surface area of the etched foil.The effect of sulfuric acid concentration and electropolymerization constant voltage on the corrosion foil was discussed through a single-factor experiment.The conditions of surface modification of high-purity aluminum foil electropolymerization were obtained through comprehensive analysis: the monomer concentration was 0.2 mol/L,the sulfuric acid concentration was ?0.25 mol/L,and the voltage was 0.4V-2.0V.By analyzing the morphology of the polymer prepared by electropolymerization on the surface of aluminum foil,polyaniline was obtained as a polyaniline film with a length of about 1 ?m and a diameter of about 500 nm superimposed on the surface of the aluminum foil.Polypyrrole is a polypyrrole film in which the spheres with a diameter of about 1 ?m are stacked and arranged on the surface of the aluminum foil.Polythiophene is a polythiophene film composed of tens of nanometer diameter spheres stacked on the surface of an aluminum foil.Electrochemical test method analysis of experimental data shows that the high-purity aluminum foil in the acidic solution corrosion steady-state polarization curve scanning speed of 0.005V/s.The addition of sodium nitrate and conductive polymer will cause the aluminum foil to erode negatively to the electrode potential.The open circuit potential also shifts negatively with increasing sodium nitrate concentration.The electrochemical corrosion reaction is more likely to occur.The open circuit potential is basically stable at about 80 s,but excessive concentration of sodium nitrate leads to severe over corrosion of the surface of the corroded aluminum foil.The concentration of sodium nitrate should be controlled at 0.3 mol/L.Electrochemical impedance spectroscopy of electropolymerized surface-modified aluminum foil in this acidic solution showed that the capacitive-resistance arc of the corroded aluminum foil electrode became larger and r(PTh)>r(PAn)>r(PPy),ie,the greater the polarization resistance.The stronger the corrosion inhibition effect on the aluminum foil surface.