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dc.contributor.authorMonzel, William Jacoben_US
dc.date.accessioned2017-04-24T16:03:05Z
dc.date.available2017-04-24T16:03:05Z
dc.date.issued2014-05-01en_US
dc.identifier.otheretd-05122014-183351en_US
dc.identifier.urihttp://hdl.handle.net/10919/77501
dc.description.abstractThe ultimate goal of this research was to gain a more fundamental understanding of the effects of “active"? alloying elements on the performance of low voltage, aluminum, sacrificial anodes. We have developed an overview of elemental trends and a comparison with literature, in support of a larger program on predicting anode behavior. The broader impact of this work was to enhance the ability to control corrosion and reduce the likelihood of hydrogen embrittlement induced by cathodic protection on ships and marine structures. As compared to high voltage anodes, low voltage, aluminum, sacrificial anodes reduce the likelihood of causing hydrogen embrittlement or stress corrosion cracking when used to protect high strength steels. In this study, open circuit potential, potentiostatic, galvanostatic and Tafel tests were performed on eleven high-purity aluminum-based binary and ternary alloys containing Bi, Ga, In and Zn in an effort to understand the individual effects of each element and the interactions between these elements. The microstructures of the as-cast alloys and the corrosion surfaces after testing were characterized using electron microscopy. Current capacities and current capacity efficiencies were calculated from potentiostatic and galvanostatic data. Galvanic coupling data from Druschitz et al was plotted with average values from potentiostatic and galvanostatic tests on Tafel curves for all alloys. [1] Variance of weight loss, average galvanostatic current, and average potentiostatic potential of the Al-0.57 wt% Zn-0.55 wt% Bi alloy was evaluated. Indium and gallium had the most significant effect on corrosion behavior (per wt% added), followed by zinc and bismuth. Bismuth had only a small effect on the weight loss, galvanostatic current and potentiostatic potential. However during potentiostatic testing Al-Bi alloys showed a steady increase in current with time, indicating that larger effects may be seen at longer periods of time. In Al-Zn alloys preferential dissolution of the zinc-rich interdendritic regions was observed. The Al-5.3 wt% Zn alloy showed high current values, but also exhibited high weight loss and more adherent corrosion products. Interdendritic corrosion also occurred with the Al-5.3 Zn-0.011 In alloy. Also, non-uniform dissolution of the remaining primary aluminum dendrites by the formation of small holes was observed, possibly due to indium precipitates. Grain boundary attack and severe intra-granular pitting was observed in Al-In alloys. Small holes were also evident on the surface of pits, similar to those seen on dendrites with the Al-5.3 Zn-0.011 In alloy. The addition of Indium greatly shifted voltages to more negative values (-0.802 to -0.858 VSCE at 9 A/m²) and significantly increased the observed currents (42-83 A/m² at -0.730 VSCE). High potentiostatic current capacities were exhibited by Al-In alloys, Al-0.1 wt% Ga, Al-5.3 wt% Zn-0.011 wt% In, and Al-0.57 wt% Zn-0.55 wt% Bi. However some calculated current capacity values were actually above the theoretical values, possibly due to corrosion products affecting the weight loss measurements.
dc.language.isoen_USen_US
dc.publisherVirginia Techen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectCorrosionen_US
dc.subjectAluminumen_US
dc.subjectAnodeen_US
dc.subjectSacrificialen_US
dc.subjectLow-Voltageen_US
dc.titleInvestigation of New, Low-Voltage, Aluminum, Sacrificial Anode Chemistriesen_US
dc.typeThesisen_US
dc.contributor.departmentMaterials Science and Engineeringen_US
dc.description.degreeMaster of Scienceen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineMaterials Science and Engineeringen_US
dc.contributor.committeechairDruschitz, Alan P.en_US
dc.contributor.committeememberCorcoran, Sean G.en_US
dc.contributor.committeememberReynolds, William T.en_US
dc.type.dcmitypeTexten_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05122014-183351/en_US
dc.date.sdate2014-05-12en_US
dc.date.rdate2017-08-20
dc.date.adate2014-06-30en_US


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