Breakdown Kinetics at Nanostructure Defects of Passive Films

Kinetics expressions for passivity breakdown have been determined based on a model taking into account the presence of intergranular defective sites in passive films. It is shown that depending on the interface at which the potential drop increase predominates, passivity breakdown can occur by enhanced dissolution (i.e., oxide thinning) at the oxide/electrolyte interface or by accelerated interfacial voiding at the metal/oxide interface. In all cases, the rate of the interfacial processes leading to passivity breakdown is increased at the intergranular defective sites of the passive film. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3186644] All rights reserved.