Research On Electro-etching And Hydrophobicity Of High Specific Capacity Anode Foil For Aluminum Electrolytic Capacitors

The capacitance of the capacitor is determined by the formula C=εS/4πkd.Increasing the surface area of the anode foil of the aluminum electrolytic capacitor is of great value for obtaining a high-capacity aluminum electrolytic capacitor.In this paper,the effect of chemical immersion pretreatment on anode aluminum foil before hole formation on anode aluminum foil performance was studied.In the corrosion expansion process,the addition of polystyrene sulfonic acid（PSS）as a corrosion inhibitor to the anode was investigated.Influence of foil properties.Secondly,the superhydrophobicity and corrosion resistance of aluminum foil surface modified by stearic acid（STA）were studied by electrochemical etching.The microstructure and electrochemical behavior of anode aluminum foil before and after alkaline washing were characterized in the pretreatment.The anode aluminum foil was chemically immersed with different concentrations of Cu（NO₃）₂ solution to characterize the surface and cross-section morphology of the pores,and analyze the relevant parameters such as the weight loss rate of corrosion,electrochemistry and specific volume.Electrolytic corrosion of anode aluminum foil was carried out by adding different concentrations of corrosion inhibitors（PSS）to the pore expanding solution.The effects of the corrosion inhibitors on microscopic morphology,specific volume and mechanical properties were studied.In the analysis method,SEM,electrochemical workstation,X-ray diffractometer and LCR digital bridge were used to test the samples.The analysis of micro-morphology shows that the deposition of trace inert metals during pretreatment can accelerate the electrolytic corrosion,significantly increase the pore density of the anode aluminum foil,increase the weight loss rate from 5%to 9%,and increase the specific capacitance by 10%to 15%.The introduction of PSS in the corrosion expansion can change the morphology of the etched pores,reduce the thermochemical self-corrosion effect on the surface of the anode aluminum foil,increase the specific capacitance of the anode foil by about 0.1μF·cm^-2,and the weight loss rate from corrosion is 17%Down to 14%.The bending strength increased to 52times,which effectively improved the stability of the anode aluminum foil.The electrochemical etching of micro-and nano-scale rough structures and the deposition of stearic acid film on the surface of aluminum foil will make the surface appear superhydrophobic.The contact angle of aluminum foil will increase from 40°to 160°when untreated,in NaCl solution.The corrosion current density has been reduced from7.497μA·cm^-2 to 0.062μA·cm^-2,which significantly improves its corrosion resistance.