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ETD Abstract Container

Abstract Header

Atmospheric Pitting Corrosion Studies of AA7075-T6 Under Electrolyte Droplets

Thomson, Mark S
http://rave.ohiolink.edu/etdc/view?acc_num=osu1461232785

Abstract Details

2016, Master of Science, Ohio State University, Materials Science and Engineering.
Pitting corrosion of AA7075-T6 was investigated in situ by Scanning Kelvin Probe (SKP) and in exposures in outdoor settings by application of droplets containing MgCl2 and NaCl. Initial droplet volumes of 3, 6 and 9 µL were used, and salt concentrations were selected at 0.1, 0.25, 0.5 and 1 M for MgCl2, and 0.25, 0.6 (3.5 wt%), and 1 M for NaCl. Analysis for all tests was conducted by optical microscope and optical profilometer. Within the droplets studied by SKP, single regions of sustained pitting attack formed with preference at the edge of the droplets due to shortened distance of oxygen diffusion. The pits at the sustained attack sites formed anodes with supporting cathodic reactions at the surrounding sample surface. As the pits grew, the cathodic region was observed to expand, leading to elevated potentials measured at the center of the droplets. Droplets with greater initial volume formed larger areas of contact with the sample surface leading to accelerated corrosion attack. Comparison of samples exposed for various lengths of time outdoors to those tested in the lab displayed different corrosion behaviors for MgCl2 and NaCl droplets. MgCl2 droplets experienced similar pitting in the lab and outdoors. However, NaCl experienced more aggressive pitting attack on samples exposed outdoors. Outdoor tests for NaCl also underwent attack along the entire perimeter of the droplets. A mechanism is proposed for this attack. Overall, sustained pitting attack is observed along groups of surface particles oriented along the rolling direction. In many cases, pitting led to the formation of a secondary droplet at the periphery of the primary droplet. A mechanism is proposed for the pitting behavior of AA7075-T6 under the studied electrolyte droplets, as well as a new mechanism for the formation of secondary droplets.
Gerald Frankel (Advisor)
Jenifer Locke (Committee Member)
Materials Science

Recommended Citations

Citations

  • Thomson, M. S. (2016). Atmospheric Pitting Corrosion Studies of AA7075-T6 Under Electrolyte Droplets [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461232785

    APA Style (7th edition)

  • Thomson, Mark. Atmospheric Pitting Corrosion Studies of AA7075-T6 Under Electrolyte Droplets. 2016. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1461232785.

    MLA Style (8th edition)

  • Thomson, Mark. "Atmospheric Pitting Corrosion Studies of AA7075-T6 Under Electrolyte Droplets." Master's thesis, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461232785

    Chicago Manual of Style (17th edition)

osu1461232785
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This open access ETD is published by The Ohio State University and OhioLINK.