Research Of Dc Etching Of Extending Surface Area Of Aluminium Foil For High-voltage Electrolytic Capacitor

The surface corrosion of anode aluminum foil is an effective method to increase the capacity of electrolytic capacitors. However, complex process of face expansion, low and inhomogeneity distribution restrict the further increase of electric capacity. Meanwhile, it is also difficult to meet the miniaturization requirements capacitance because of the anode foil's lower anti-bending performance. So this paper researched on the high voltage direct current electrode foil face expansion corrosion from extending the coverage rate of aluminum foil corrosion.Using sulfate and hydrochloride corrosion system make electrochemical corrosion experiment consist of pretreatment, occur hole and enlarge hole on the 110μm thick, 99.99% high purity aluminum light foil. Tested the bending properties of corrosion samples by special bending machine, analysesed the surface of corrosion samples by SEM, tested the sample capacity by specific volume test machine,researched on the influence of hydrochloride density, current density, temperature and corrosion time to electric capacity and bending properties of corrosion aluminum foil. Achieve the following main results:The aluminum foil can remove surface oil effectively , form a homogeneous porous oxide film, increase the wettability of aluminum foil surface which corrosion liquid etching on in the process, improve the density and uniformity of creating hole after pretreatment at 120 seconds, 60℃and (5g NaOH +1 g Na₂C₂O₄)/L solution. Meanwhile, etching of extending surface area aluminum foil has higher specific capacitance and less weight loss after pretreating.SEM analysis showed that aluminum foil corrosion hole is density and uniform, showing good creating hole etching effect after pretreatment at 2mol/L HCl ,1.5mol/L H₂SO₄ mixture, 80℃, 0.50 A/cm² current density and 140 seconds. The specific capacitance of aluminum foil can attain 0.73μF/cm² and bending reach up to 59 times after creating hole corrosion in 1mol/L HCl etching solutions, the current density of 85℃and 0.15 A/cm² at 600 seconds.Preliminary analysised the mechanism of loss initiation and pit growth of high voltage direct current corrosion. which increased Cl-concentration can increase the probability of corrosion initiation.Made the density of initial corrosion hole increase gradually with the increasing time of creating hole. The vertical push of enlarging hole corrosion can increase the effective surface area of high high voltage corrosive aluminum foil maximum.