| Popis: |
No-rinse conversion coatings based on KMnO4, were applied to aluminium alloys and pure aluminium, and examined with X-ray absorption near edge spectroscopy (XANES). Some specimens were prepared beforehand and other specimens were freshly prepared immediately before testing, so that early changes in the coatings could be studied. A significant difference in composition was found between the one-week old specimens and the fresh. The old specimens consisted predominantly of Mn oxides, while the fresh specimens contained a substantial proportion of KMnO4. When fresh specimens were rinsed with de-ionised water, soluble KMnO4 was removed and the spectrum now showed evidence for mixed oxides, but no KMnO4, like the older specimens. Monitoring of specimens after exposure to 0.5% NaCl solution showed little further change in the film. |
