Computations to elucidate the effects of microscopic nonuniformity on current flow in passive layers are extended to explore predictions in the bond percolation limit. Whereas the dependence of the leakage current on the percentage of low barriers (e.g., those promoted by Cl- in the passive layer! was found to be nearly exponential for relatively small differences in the activation energy barrier heights, the functional dependence is observed to be more complex for larger differences, manifesting a critical transition from a relatively nonconducting state to a state of sharply increasing conductivity as the percentage of lower activation barriers increases beyond the bond percolation threshold. This degrading of the insulating properties of the passive layer is postulated to constitute the condition needed for the chemical breakdown of passivity. This interpretation leads in turn to a mechanism for the experimentally noted delay in the time required before the occurrence of the relatively sudden and catastrophic breakdown of passivity after the addition of aggressive ions to the solution, the so-called induction time being that time required for the field-driven diffusion of aggressive ions to reach the critical concentration required for bond percolation. (C) 2003 The Electrochemical Society.