Atomic Force And Scanning Electron Microscopy Of Corrosion And Fatigue Of An Aluminum-Copper Alloy

Kowal, K.; DeLuccia, John J.; Josefowicz, Jack Y.; Laird, C.; Farrington, G. C.

doi:10.1557/proc-409-201

Cited by 2 publications

(2 citation statements)

References 13 publications

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“…62,63 A fourfold increase in the ratio of copper to aluminum found at the surface of AA2024-T3 was reported on exposure to acid chloride medium. 64 A mechanism for copper redistribution on the surface of AA2024-T3 based on dealloying of copper-rich intermetallic particles like Al 2 CuMg has also been shown by several workers. 4,5,44,45,65 Though shown for the s-phase (Al 2 CuMg), it was found applicable to the -phase.…”

Section: Resultsmentioning

confidence: 78%

Interactions of the Components of Chromate Conversion Coating with the Constituents of Aluminum Alloy AA2024-T3

Chidambaram¹,

Clayton²,

Halada³

2004

J. Electrochem. Soc.

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Electrochemical techniques were employed to study the nature of individual interactions between the chemicals constituting a widely used commercial chromate conversion-coating treatment and the main constituents of AA2024-T3 alloy, namely, Al ͑99.999%͒, Al 2 Cu, Al-Al 2 Cu galvanic couple, and AA2024-T3 alloy. The samples were pretreated using chromate, ferricyanide, fluoride, tetrafluoroborate, and hexafluorozirconate, prior to electrochemical corrosion tests. The results were compared with untreated ͑control͒ samples. For the first time, the chemical interaction of aluminum with hexafluorozirconate has been studied. Maximum activation was observed in the case of hexafluorozirconate pretreatment, which also decreased the interfacial tension and increased surface wetting. The electrochemistry of the control and pretreated ͑except for hexafluorozirconate pretreatment͒ AA2024-T3 and Al 2 Cu were found to be similar. The cathodic electron transfer reaction rate for oxygen reduction was found to be enhanced by the presence of copper in the systems. The enhancement was proportional to the copper content. The cathodic reaction on all systems was inhibited by chromate. Aluminum was observed to undergo cathodic corrosion, leading to an enrichment of the surface copper content and subsequent enhancement of the cathodic electron transfer reaction.

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Section: Resultsmentioning

confidence: 78%

Interactions of the Components of Chromate Conversion Coating with the Constituents of Aluminum Alloy AA2024-T3

Chidambaram¹,

Clayton²,

Halada³

2004

J. Electrochem. Soc.

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“…Localized corrosion at particles in alloys is common, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] but the details of how anodic and cathodic currents and solution pH evolve in a system containing multiple pitting sites is unknown. Interactions between pitting sites at particles in alloys 17,18 and in macroscopic wire electrodes [19][20][21] have been investigated.…”

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confidence: 99%

Current Measurements from Multiple Pitting Sites in Engineered Aluminum Electrodes

Missert

Copeland

Johnson

et al. 2012

J. Electrochem. Soc.

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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.Localized corrosion at particles in alloys is common, 1-16 but the details of how anodic and cathodic currents and solution pH evolve in a system containing multiple pitting sites is unknown. Interactions between pitting sites at particles in alloys 17, 18 and in macroscopic wire electrodes 19-21 have been investigated. One set of studies showed that when pitting is driven by polarization of particular electrodes, aggressive solution chemistries can damage the oxide on nearby electrodes and influence pit initiation at these remote sites. 19,20 Under free corrosion conditions, pitting sites on isolated Al wires displayed fluctuations in potential and current and required cathodic current from remote sites. 21 The complex microstructure found in typical alloys makes it difficult to predict where pits will develop, and whether balancing cathodic reactions at remote sites are needed for pit stabilization. 10,14,15 Model alloys have been employed to investigate several aspects of pitting such as Cu redistribution, 22 galvanic coupling, 23-26 and alkalization. 22, 27-29 The random particle size and distribution in aluminum alloys results in particle densities and anode to cathode area ratios that are not independently controlled. Furthermore, real-time, simultaneous measurements of currents at multiple pitting sites are extremely difficult.In an effort to elucidate the mechanistic details of the pitting process, pit propagation has been investigated using five individual pure Al thin film electrodes, each containing a single engineered Cu particle, as a model system for Cu-rich particles in Al-Cu alloys. This approach allows independent control of some of the variables thought to control pitting behavior in real alloys, in particular, the initial particle/matrix composition, cathode/anode area ratio, and particle distribution...

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Atomic Force And Scanning Electron Microscopy Of Corrosion And Fatigue Of An Aluminum-Copper Alloy

Cited by 2 publications

References 13 publications

Interactions of the Components of Chromate Conversion Coating with the Constituents of Aluminum Alloy AA2024-T3

Interactions of the Components of Chromate Conversion Coating with the Constituents of Aluminum Alloy AA2024-T3

Current Measurements from Multiple Pitting Sites in Engineered Aluminum Electrodes

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