Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5356812 | Applied Surface Science | 2011 | 5 Pages |
Abstract
The effect of alkaline cleaning and activation on the composition and thickness of the oxide layer on aluminum alloy 7075-T6 was studied. E-pH diagrams were developed to predict the effect of alkaline cleaning and activation solutions on the stability of the oxide surface layers. The thickness of the native oxide layer was determined to be â¼30Â nm by Auger electron spectroscopy depth profiling analysis. The outer â¼20Â nm was rich in magnesium while the remaining â¼10Â nm was rich in aluminum. Cleaning in a 9.1 pH alkaline solution was found to remove the magnesium-rich layer and leave behind an aluminum-rich oxide layer â¼10Â nm thick. Activation in alkaline solutions of NaOH (pHÂ >Â 12.9) or Na2CO3 (pHÂ >Â 11.5) produced an oxide that was â¼20 to 60Â nm thick and rich in magnesium. Alkaline cleaning and activation altered the oxide composition and thickness making it possible for deposition of thicker cerium-based conversion coatings (â¼100 to 250Â nm) compared to only alkaline cleaning (â¼30Â nm), with application of one spray cycle of deposition solution.
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Authors
Simon Joshi, William G. Fahrenholtz, Matthew J. O'Keefe,