Pit growth behavior on aluminum under potentiostatic control

The growth behavior of pits on aluminum is studied during potentiostatic etching with current transient measurement, SEM and AFM observation. The results show that there is an induction period for the pit nucleation. The current rises to a maximum and then a plateau appears during the etching. Hemispherical pits form and grow in size before the plateau, and transform into half-cubic pits at the plateau. The change of the pitting behavior is controlled by the current density for pitting.