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Journal of the Electrochemical Society, Vol.159, No.6, C259-C264, 2012
Current Measurements from Multiple Pitting Sites in Engineered Aluminum Electrodes
Corrosion of aluminum in a system of engineered copper particles was studied in order to elucidate the nature of the interactions between multiple pitting sites. Single copper particles were fabricated on isolated, thin-film aluminum electrodes to enable independent measurements of excess anodic and cathodic currents flowing during open circuit exposures to dilute aqueous chloride solutions. In-situ fluorescence microscopy allowed imaging of local changes in solution pH during the exposure. Under the experimental conditions explored here, the anodic dissolution of aluminum beneath the majority of particles was balanced by cathodic reactions on the same electrode. However, excess anodic currents were also observed on some single electrodes due to accelerated dissolution of aluminum beneath the copper particles. These excess anodic currents were balanced by cathodic currents distributed between the other electrodes. Fluctuations in the excess anodic currents were correlated with fluctuations in the open circuit potential and with localized increases in solution pH above each of the copper particles. The transient nature of this accelerated dissolution suggests that it may evolve under anodic control. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.008206jes] All rights reserved.