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Title: Tracer Film Growth Study of the Corrosion of Magnesium Alloys AZ31B and ZE10A in 0.01% NaCl Solution

We conducted a sequential isotopic tracer study of corrosion film growth for Mg-3Al-1Zn-0.25Mn (AZ31B) and Mg-1.2Zn-0.25Zr-<0.5Nd (ZE10A) by 4 h immersion in H 2 18O or D 2 16O, followed by a 20 h immersion in a 0.01 wt% NaCl H 2 18O or D 2 16O solution. Sputter depth profiles were obtained for 16O, 18O, H, and D using secondary ion mass spectrometry (SIMS). When compared to the previous tracer study for these alloys in salt-free water, the addition of 0.01 wt% NaCl resulted in a transition from oxygen inward-dominated film growth to a component of mixed inward/outward film growth for both alloys. The hydrogen tracer behavior remained inward growing for AZ31B, and short-circuit, inward growing for ZE10A, in both pure water and in 0.01 wt% NaCl solution, with extensive penetration of D beyond the film and into the underlying alloy also observed for ZE10A. Our analysis of the films by X-ray photoelectron spectroscopy (XPS) and cross-section scanning transmission electron microscopy (STEM) indicated intermixed Mg(OH) 2 and MgO, with the relative fraction of Mg(OH) 2 peaking near the center of the film. These findings suggest a decoupled film growth mechanism, with initial formation of oxide followed by NaCl-accelerated conversionmore » to hydroxide, likely by both solid-state and dissolution-precipitation processes.« less
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ; ORCiD logo [1] ;  [3]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Manitoba, Winnipeg, MB (Canada)
  3. Magnesium Elektron North America, Madison, IL (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 164; Journal Issue: 7; Journal ID: ISSN 0013-4651
Publisher:
The Electrochemical Society
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1360066