Passivity of 4N pure aluminum sheet for electrolytic capacitor electrodes

The effect of degreasing treatments on the passivity of pure aluminum sheets 99.99 mass%.for electrolytic capacitor electrodes has been investigated in terms of surface oxide film characteristics. The polarization resistance Rp.measured by AC impedance measurement in 1 N HCl was dependent on the conditions of degreasing treatments e.g., organic solvent, alkaline cleaner.. The XPS measurement for O1s binding energy and the SIMS measurement for the secondary ion intensity of AlOq revealed that degreasing treatments effect the composition at the surface of oxide film. NaOH solution and alkaline cleaner caused a number of –OH sites to increase. In addition, there was an inverse relationship between the logarithm of the relative intensity of AlOq and the Epit pitting potential.in 3.5% NaCl. Therefore it is considered that the great number of –OH sites at the surface due to degreasing treatments, through which Cly ions can penetrate, have the larger effect on the passivity of pure aluminum sheets. q1999 Elsevier Science B.V. All rights reserved