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Pretreatments of Al-2024 T3 alloy for BTSE silane deposition Lee, Michael Che-Chiang
Abstract
Work in this thesis studied different alkaline etching procedures performed on Al-2024 alloy prior to deposition of bis-triethoxysilylethane (BTSE). X-ray photoelectron spectroscopy and scanning electron microscopy were used to study the chemistry and morphology of the surfaces formed after the various pretreatments and coatings have been applied. The corrosion performance of these samples were assessed using polarisation curve measurements and immersion testing. Sonicating tests were performed to determine, semi-quantitatively, the adhesion of BTSE to Al-2024 panels after application of the various pretreatments. Alkaline etching of the coated and uncoated Al-2024 panels was performed using 10% NaOH in deionised water, varying the duration of the treatment from 1 minute to 10 minutes. It is shown on uncoated Al-2024 that longer etching times increase surface roughness of the substrate, but also reduce corrosion resistance, cause copper enrichment at the surface, and form loosely-bonded etching products which affect the subsequent silane deposition steps. BTSE solutions varying from 1% to 10% (v/v) BTSE were used to coat the pretreated panels. It is found that BTSE-coated samples perform better than their uncoated counterparts in corrosion testing, and that more-concentrated BTSE solutions on identically prepared panels produce thicker coatings, with better passivation. It is also found that, while increasing the alkaline etching time may lead to conditions where more BTSE is deposited to the surface, this "enhanced" silane layer is not as securely-bonded to the surface and will not aid in the passivation of the substrate. Finally, the effects of the HNO₃ desmutting step were studied by varying the treatment times that the Al-2024 panels received in 10% FINO₃ after 1 minute of alkaline etching. It is found that for up to 30 minutes of treatment, FINO₃ is beneficial to silane deposition as it removes the etching product created during the NaOH treatment, builds up the oxide layer and creates more sites for the silane bonding. However, with longer exposure, HNO₃ acts as a corrosion agent removing previously-built oxide layer which reduces the amount of securely-bonded BTSE.
Item Metadata
Title |
Pretreatments of Al-2024 T3 alloy for BTSE silane deposition
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2002
|
Description |
Work in this thesis studied different alkaline etching procedures performed on
Al-2024 alloy prior to deposition of bis-triethoxysilylethane (BTSE). X-ray photoelectron
spectroscopy and scanning electron microscopy were used to study the chemistry and
morphology of the surfaces formed after the various pretreatments and coatings have
been applied. The corrosion performance of these samples were assessed using
polarisation curve measurements and immersion testing. Sonicating tests were performed
to determine, semi-quantitatively, the adhesion of BTSE to Al-2024 panels after
application of the various pretreatments.
Alkaline etching of the coated and uncoated Al-2024 panels was performed using
10% NaOH in deionised water, varying the duration of the treatment from 1 minute to 10
minutes. It is shown on uncoated Al-2024 that longer etching times increase surface
roughness of the substrate, but also reduce corrosion resistance, cause copper enrichment
at the surface, and form loosely-bonded etching products which affect the subsequent
silane deposition steps.
BTSE solutions varying from 1% to 10% (v/v) BTSE were used to coat the
pretreated panels. It is found that BTSE-coated samples perform better than their
uncoated counterparts in corrosion testing, and that more-concentrated BTSE solutions
on identically prepared panels produce thicker coatings, with better passivation. It is also
found that, while increasing the alkaline etching time may lead to conditions where more
BTSE is deposited to the surface, this "enhanced" silane layer is not as securely-bonded
to the surface and will not aid in the passivation of the substrate.
Finally, the effects of the HNO₃ desmutting step were studied by varying the
treatment times that the Al-2024 panels received in 10% FINO₃ after 1 minute of alkaline
etching. It is found that for up to 30 minutes of treatment, FINO₃ is beneficial to silane
deposition as it removes the etching product created during the NaOH treatment, builds
up the oxide layer and creates more sites for the silane bonding. However, with longer
exposure, HNO₃ acts as a corrosion agent removing previously-built oxide layer which
reduces the amount of securely-bonded BTSE.
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Extent |
4627268 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-10-28
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0061289
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2003-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.