Repassivation Transients Measured with the Breaking‐Electrode Technique on Aluminum Thin‐Film Samples

The breaking-electrode technique was used to study repassivation transients of small, fresh metal areas of Al exposed to a conductive electrolyte at a range of potentials. The peak current density measured within the first few microseconds after breaking was found to be ohmically limited, with an ohmic resistance that is substantially higher than that measured minutes after breaking. The current decay during the first 3 s was recorded and found to be exponential in nature. By plotting the data as log i vs. (it) -1/2 , it is concluded that oxide growth was better.represented by the direct logarithmic law than by high-field kinetics. Cathodic current transients having a complex shape Were observed at low potentials. It is suggested that oxide growth at potentials slightly above the reversible potential for oxide formation retards the water reduction reaction. The advantages and limitations of the breaking-electrode technique are discussed.