IMPEDANCE MEASUREMENTS DURING ANODIZATION OF ALUMINUM

The impedance of a growing anodic oxide layer is inductive in a certain frequency range. This effect is related to the occurrence of transients after changes in current density or applied electric field. Measurements on aluminum samples in the frequency range 5 mHz-10 kHz and the current density range 3 X 10~6-5 X 10-3 A/cm2 and in various electrolytes are presented and compared with a theory in which the relaxation effect is ascribed to a buildup of surface charge at the metal-oxide interface. © 1979, The Electrochemical Society, Inc. All rights reserved.