Document Type

Article

Research Focus Area

Advanced and Nanostructured Materials

Publication Date

1994

Journal or Book Title

Journal of the Electrochemical Society

Volume

141

Issue

12

First Page

3361

Last Page

3368

DOI

10.1149/1.2059340

Abstract

Near‐surface atomic‐scale defects in aluminum foils of at least 99.98% purity were characterized with positron annihilation spectroscopy measurements of the Doppler‐broadening parameter S. Profiles of S vs. positron beam energy (i.e., vs. depth into the sample) were analyzed with a model for positron diffusion and trapping in order to characterize the defect layer structure. As‐received foils were shown to possess a defect layer within 10 to 100 nm of the oxide film/metal interface. Both dissolution in aqueous sodium hydroxide solution and anodic pitting corrosion in caused significant changes in the position spectra which were interpreted as increases in the defect population. On the basis of isochronal annealing, the defects were impurity‐complexed voids or vacancy clusters, or else interfacial voids at the metal/film boundary located at surface roughness features. Either case suggests a possible role for the defects as pit sites, since both near‐surface impurities and surface roughness are known to influence the number of pits on a surface. Defects found after pitting may be present in layers surrounding individual pits, and might have been produced in the process of pit initiation.

Comments

This article is from Journal of the Electrochemical Society 141 (1994): 3361–3368, doi:10.1149/1.2059340. Posted with permission.

Copyright Owner

ECS—The Electrochemical Society

Language

en

File Format

application/pdf

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