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Title: Passivity behavior of melt-spun Mg-Y Alloys
Authors: Yao, H.B.
Li, Y. 
Wee, A.T.S. 
Keywords: Incorporation
Native film
Passive film
Issue Date: 15-Dec-2003
Citation: Yao, H.B., Li, Y., Wee, A.T.S. (2003-12-15). Passivity behavior of melt-spun Mg-Y Alloys. Electrochimica Acta 48 (28) : 4197-4204. ScholarBank@NUS Repository.
Abstract: Several Mg-Y binary ribbons with Y content up to ∼ 17.9 at.% were fabricated by melt-spinning. X-ray diffraction (XRD) revealed that the phase structure changes with increasing Y content from extended solid solution to partially amorphous, and then fully intermetallic Mg24Y5. Anodic potentiodynamic polarization performed in 0.01M NaCl electrolyte (pH = 12) revealed improved anodic passivity behavior compared to pure Mg for all the Mg-Y alloys. X-ray photoelectron spectroscopy (XPS) revealed that the improved passivity of Mg-Y was more related to the elemental oxidation state rather than the concentration of the surface components. To study the effect of Cl - ion on the passivity behavior, anodic potentiodynamic and potentiostatic polarization were performed on Mg-17.9at.% Y in alkaline (pH = 12) NaCl electrolytes containing Cl- ion in the concentration range from 0.00 to 0.50 M. The passive films formed in 0.01 M NaCl electrolyte were similar to the native film, which were composed of MgO and Y2O 3. No CO3 2- and Cl- ions were incorporated into the passive film. The passivity was significantly degraded in the electrolytes containing higher Cl- concentration (0.1 and 0.5 M). Detailed XPS revealed that the surface films under these conditions were composed of much hydrated species Mg(OH)2 and YOOH and/or Y(OH) 3 and CO3 2- was incorporated into the surface film. The incorporation of Y2O3 in the passive film was given as the reason for the enhanced passivity properties of Mg-Y ribbons. The mechanism of Cl- and CO3 2- ions to the degradation of the passivity was discussed. © 2003 Elsevier Ltd. All rights reserved.
Source Title: Electrochimica Acta
ISSN: 00134686
DOI: 10.1016/S0013-4686(03)00605-4
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