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Corrosion Protection of Aluminum Alloy 2024-T3 by Al-Rich Primer

Wang, Xi
http://orcid.org/0000-0002-5953-2787
http://rave.ohiolink.edu/etdc/view?acc_num=osu1557143060015145

Abstract Details

2019, Doctor of Philosophy, Ohio State University, Materials Science and Engineering.
Metal-rich primers have been used for corrosion protection on metals for over 40 years. Recently, researchers started to investigate the use of metal-rich primers on aluminum alloys as an alternative to hexavalent-chromate systems because of their good corrosion-protective properties. The active aluminum-rich primer (AlRP) was invented and developed at NAVAIR (Patuxent River, MD) to protect aluminum alloys and steels. The Al alloy (Al-Zn-In) pigments in AlRP were fabricated from a sacrificial anode alloy, which has a lower open circuit potential (OCP) than common aluminum alloys. However, initial results indicated that the pigment particles in AlRP tended to undergo severe self-corrosion. Therefore, the Al pigments are pretreated in a trivalent chromium passivation (TCP) bath to reduce the self-corrosion rate. The objectives of this study are to understand the corrosion protection properties of AlRP on aluminum alloy 2024-T3 substrate and to evaluate the effect of TCP treatment on the Al pigment particles. The polarization curves of AA2024-T3 and the active aluminum alloy (Al-Zn-In) show that TCP-treated active aluminum alloy has a lower corrosion potential than AA2024-T3 and thus would cathodically protect it. AlRP-coated samples were exposed in accelerated exposure tests, GMW14872 and B117. Exposed samples were then examined using scanning electron microscopy and energy dispersive X-ray spectroscopy to understand the coating degradation process. In addition, samples were immersed in 0.1M NaCl solution for an extended time and were monitored using electrochemical impedance spectroscopy. The AlRP with TCP-treated pigments out performs the coating with untreated pigments. The TCP treatment on the Al-Zn-In pigments was evaluated. The chemistry and morphology of Al pigment particles treated in a TCP bath for three different immersion times were characterized using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The corrosion protection properties of TCP were evaluated using potentiodynamic polarization. A strong effect of treatment time was found. The TCP coating structure on Al-Zn-In pigments is similar to that found previously on bulk substrates composed of other aluminum alloys as it has a bilayer structure. Overall, the AlRP with pigment particles treated with 5 min TCP had the best corrosion protection to the substrate because of the optimized pigment particle surface treatment.
Gerald Frankel (Advisor)
Jenifer Locke (Committee Member)
Narasi Sridhar (Committee Member)
164 p.
Materials Science
Al-rich Primer; AA2024-T3; Al-Zn-In; aluminum alloys; cathodic protection; EIS; transmission line model; SEM; TEM; trivalent chrome process; TCP; B117; GMW14872; polarization; coating; pretreatment; corrosion; epoxy

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Citations

  • Wang, X. (2019). Corrosion Protection of Aluminum Alloy 2024-T3 by Al-Rich Primer [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557143060015145

    APA Style (7th edition)

  • Wang, Xi. Corrosion Protection of Aluminum Alloy 2024-T3 by Al-Rich Primer. 2019. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1557143060015145.

    MLA Style (8th edition)

  • Wang, Xi. "Corrosion Protection of Aluminum Alloy 2024-T3 by Al-Rich Primer." Doctoral dissertation, Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557143060015145

    Chicago Manual of Style (17th edition)

osu1557143060015145
719
© 2019, some rights reserved.Creative Commons License Corrosion Protection of Aluminum Alloy 2024-T3 by Al-Rich Primer by Xi Wang is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by The Ohio State University and OhioLINK.