Document Type

Article

Research Focus Area

Advanced and Nanostructured Materials

Publication Date

2001

Journal or Book Title

Journal of the Electrochemical Society

Volume

148

Issue

24

First Page

B92

Last Page

B100

DOI

10.1149/1.1341241

Abstract

High-purity aluminum foils were examined using positron annihilation spectroscopy (PAS) after dissolution for various times in 1 M NaOH at room temperature. Measurements of the S and W shape parameters of the annihilation photopeak at 511 keV show the presence of voids of at least nanometer dimension located at the metal-oxide film interface. The large Sparameter suggests that the metallic surface of the void is free of oxide. Voids are found in as-received foils and are also produced by dissolution in NaOH, evidently by a solid-state interfacial process. Atomic force microscopy (AFM) images of NaOH-dissolved foils, after stripping the surface oxide film in chromic-phosphoric acid bath, reveal cavities on the order of 100 nm size. The average cavity depth is in quantitative agreement with the PAS-derived thickness of the interfacial void-containing layer, and the dissolution time dependence of the defect layer S parameter closely parallels that of the fractional coverage of the foil surface by cavities; thus, the cavities are believed to be interfacial voids created along with those detected by PAS. The cavity distribution on the surface closely resembles that of corrosion pits formed by anodic etching in 1 M HCl, thereby suggesting that the interfacial voids revealed by AFM serve as sites for pit initiation.

Comments

This article is from Journal of the Electrochemical Society 148 (2001): B92–B100, doi:10.1149/1.1341241. Posted with permission.

Copyright Owner

ECS—The Electrochemical Society

Language

en

File Format

application/pdf

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