An EXAFS investigation of molybdate-based conversion coatings

The composition of molybdate-based conversion coatings on zinc-nickel alloy electrodeposits was examined by extended X-ray absorption fine structure (EXAFS). The absorption spectra from appropriate standards showed distinct differences between the Mo(IV) and Mo(VI) oxidation states. A pre-edge peak...

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Bibliographic Details
Published in:Journal of applied electrochemistry 2003-07, Vol.33 (7), p.553-561
Main Authors: WHARTON, J. A, ROSS, D. H, TREACY, G. M, WILCOX, G. D, BALDWIN, K. R
Format: Article
Language:English
Subjects:
Applied sciences
Corrosion
Corrosion prevention
Exact sciences and technology
Metals. Metallurgy
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Summary:The composition of molybdate-based conversion coatings on zinc-nickel alloy electrodeposits was examined by extended X-ray absorption fine structure (EXAFS). The absorption spectra from appropriate standards showed distinct differences between the Mo(IV) and Mo(VI) oxidation states. A pre-edge peak was apparent for the various molybdate species and molybdenum trioxide, with the energy and intensity dependent on the coordination of the molybdenum. A shift in the molybdenum K-edge spectra was also evident between Mo(IV) and Mo(VI) compounds. A qualitative analysis revealed that both Mo(IV) and Mo(VI) species were present within the molybdate-based conversion coating, with a significant prevalence of hexavalent molybdenum.
ISSN:0021-891X
1572-8838
DOI:10.1023/A:1024911119051