Effects of prior cathodic polarization on crystallographic pit initiation on aluminum

The growth behavior of crystallographic pits on aluminum is examined during galvanostatic anodic etching with consideration of the effect of prior cathodic polarization. Pit density and size distribution are measured by using scanning electron microscope. The results show that prior cathodic polarization enhances pit nucleation greatly and the pit number density can be increased by 11 times with a cathodic current pulse of 100mAcm^-2, 200ms. Cathodic polarization leads to passivation of a substantial number of small pits, which alters the pit size distribution. The amount of cathodic charge is a main determinant of the effects.