Effect of Pretreatment on the Pitting Corrosion of the Anode Foils for the Aluminum Electrolytic Capacitor

Anodes of aluminum electrolytic capacitor, which require large surface area for a high capacitance, are prepared in hot chloride solution to get numerous <100> etching tunnel. With the defect on the surface of the foils, the size and distribution of etch pits are not uniform. This paper compared the effect of five different pretreatment conditions on pitting corrosion of the anode aluminum foils by analyzing the morphology, the density and the distribution of the etching tunnels. It was shown that pretreatment with alkaline washing firstly to get rid of the oil stain and distorted oxidation film, and H3PO4 soaking sequentially to produce uniform oxide films, was beneficial for the uniform pitting corrosion.