The role of magnesium silicide (Mg2Si) and silicon (Si) particles in the localized corrosion of aluminum (Al) alloys was investigated herein. Sub-micrometer-sized Mg2Si and Si particles were grown in the Al matrix of Al-Mg-Si and Al-Si alloys, respectively, and characterized by transmission electron microscopy (TEM). A quasi in situ TEM technique was used to study an identical location containing Mg2Si or Si particle in the Al matrix, prior to and following a period of immersion in 0.1 M NaCl at pH 6, 2, and 12. At pH 6 and 2, Mg2Si was initially “anodic,” preferentially dealloying via selective dissolution of Mg, resulting in the development of SiO-rich remnants that are electrochemically inert. The SiO-rich remnants at pH 2 physically detached from the Al matrix. Silicon particles were electrochemically inert at pH 6, while “cathodic” at pH 2, dissolving the Al matrix at their periphery. It was observed that copper (Cu) was redeposited on Si particles at pH 2. At pH 12, Mg2Si and Si were “cathodic” to the Al matrix. This study clarifies, and provides new insights into, the characteristics of Al alloy physical manifestation of corrosion associated with Mg2Si and Si at the nanoscale.
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1 May 2020
Research Article|
March 18 2020
Clarifying the Role of Mg2Si and Si in Localized Corrosion of Aluminum Alloys by Quasi In Situ Transmission Electron Microscopy Available to Purchase
Shravan K. Kairy;
Shravan K. Kairy
‡
*Department of Materials Science and Engineering, Monash University, Clayton, VIC, 3800, Australia.
‡Corresponding author. E-mail: [email protected]; [email protected].
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Nick Birbilis
Nick Birbilis
‡
**College of Engineering and Computer Science, The Australian National University, Acton, ACT, 2601, Australia.
‡Corresponding author. E-mail: [email protected]; [email protected].
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‡Corresponding author. E-mail: [email protected]; [email protected].
Received:
February 16 2020
Revision Received:
March 18 2020
Accepted:
March 18 2020
Online ISSN: 1938-159X
Print ISSN: 0010-9312
© 2020, NACE International
2020
CORROSION (2020) 76 (5): 464–475.
Article history
Received:
February 16 2020
Revision Received:
March 18 2020
Accepted:
March 18 2020
Citation
Shravan K. Kairy, Nick Birbilis; Clarifying the Role of Mg2Si and Si in Localized Corrosion of Aluminum Alloys by Quasi In Situ Transmission Electron Microscopy. CORROSION 1 May 2020; 76 (5): 464–475. https://doi.org/10.5006/3457
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