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New insights into the fundamental chemical nature of ionic liquid film formation on magnesium alloy surfaces

journal contribution
posted on 14.04.2009, 00:00 authored by Maria ForsythMaria Forsyth, W Neil, Patrick HowlettPatrick Howlett, D Macfarlane, Bruce HintonBruce Hinton, N Rocher, T Kemp, M Smith
Ionic liquids (ILs) based on trihexyltetradecylphosphonium coupled with either diphenylphosphate or bis(trifluoromethanesulfonyl)amide have been shown to react with magnesium alloy surfaces, leading to the formation a surface film that can improve the corrosion resistance of the alloy. The morphology and microstructure of the magnesium surface seems critical in determining the nature of the interphase, with grain boundary phases and intermetallics within the grain, rich in zirconium and zinc, showing almost no interaction with the IL and thereby resulting in a heterogeneous surface film. This has been explained, on the basis of solid-state NMR evidence, as being due to the extremely low reactivity of the native oxide films on the intermetallics (ZrO2 and ZnO) with the IL as compared with the magnesium-rich matrix where a magnesium hydroxide and/or carbonate inorganic surface is likely. Solid-state NMR characterization of the ZE41 alloy surface treated with the IL based on (Tf)2N− indicates that this anion reacts to form a metal fluoride rich surface in addition to an organic component. The diphenylphosphate anion also seems to undergo an additional chemical process on the metal surface, indicating that film formation on the metal is not a simple chemical interaction between the components of the IL and the substrate but may involve electrochemical processes.

History

Journal

ACS applied materials & interfaces

Volume

1

Issue

5

Pagination

1045 - 1052

Publisher

American Chemical Society

Location

Washington D.C.

ISSN

1944-8244

eISSN

1944-8252

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2009, American Chemical Society