FORMATION OF CHROMATE CONVERSION COATINGS ON ALUMINUM AND ITS ALLOYS: AN IN SITU XANES STUDY.
Conference
·
OSTI ID:789437
- BROOKHAVEN NATIONAL LABORATORY
We used in situ X-ray adsorption near-edge structure (XANES) to investigate the formation of chromate conversion coatings on pure Al, commercial Al alloys (AA 1100, AA2024, and AA7075), and a series of binary Al-Cu alloys. The method employed a new electrochemical cell that can determine the ratio of hexavalent chromium (Cr(VI)) to total chromium (Cr(total)) speciation in conversion coatings as a function of exposure time to a chromate solution. The spectra showed that the initial Cr(VI)/Cr(total) ratios are greater than later ones for pure Al and AA1100, but not for AA2024 and AA7075. Measurements with Al-Cu alloys demonstrated that the difference observed in AA2024 and AA7075 may not be due to Cu alloying. The proportion of Cr(VI) in the coatings becomes approximately constant after 180 s of exposure for all the specimens examined even though the coatings continue to grow.
- Research Organization:
- Brookhaven National Lab., Upton, NY (US)
- Sponsoring Organization:
- DOE/SC (US)
- DOE Contract Number:
- AC02-98CH10886
- OSTI ID:
- 789437
- Report Number(s):
- BNL--68740; KC0201020; KC0201020
- Country of Publication:
- United States
- Language:
- English
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