AVS 45th International Symposium
    Applied Surface Science Division Monday Sessions
       Session AS-MoA

Paper AS-MoA10
Influence of Mg on the Oxide Formation on Al@footnote 1@

Monday, November 2, 1998, 5:00 pm, Room 307

Session: Oxides and Insulators - Surface Characterization and Applications
Presenter: D.R. Baer, Pacific Northwest National Laboratory
Authors: D.R. Baer, Pacific Northwest National Laboratory
C.F. Windisch, Jr., Pacific Northwest National Laboratory
M.H. Engelhard, Pacific Northwest National Laboratory
M.J. Danielson, Pacific Northwest National Laboratory
Correspondent: Click to Email
In an effort to increase the strength of lightweight, non-heat treatable Al alloys, Mg is a common alloy addition. However, particularly due to changes in alloy structure and chemical distribution during processing and welding, these alloys can be susceptible to grain boundary dissolution, stress corrosion cracking or hydrogen induced cracking. In an effort to understand the influence of Mg segregation and second phase formation on the electrochemical behavior and corrosion behavior of Al, we have exposed freshly cleaned surfaces of Al, Mg-implanted Al and Al@sub 3@Mg@sub 2@ to a salt solution. These cleaned surfaces are moved to the solution through a transfer system that exposes the cleaned specimens only to vacuum or a nitrogen environment (with some water vapor) before immersion into the salt solution. The open circuit corrosion potential is measured for each sample. After a short exposure, the specimens are quickly rinsed with clean water, pumped to vacuum conditions and moved into a spectrometer for XPS analysis. Specimens are also analyzed by SEM imaging and AES in a different spectrometer. Measurements show that Mg influences the corrosion potential of the material and changes the nature of the film. When Mg is present in the alloy at levels of approximately 4 at%, the oxides that form are no longer smooth but rumpled. The outer oxide that formed during solution exposure contains no observable Mg, but regions below this alumina layer are rich in oxidized Mg. This film is compared to those that form on pure Al and the beta phase Al@sub 3@Mg@sub 2@. @FootnoteText@ @footnote 1@This research was conducted at the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) with funding provided by the U.S. Department of Energy, Office of Basic Energy Sciences. The EMSL is a new DOE scientific user facility located at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington. PNNL is operated by Battelle for the Department of Energy.