Process for the preparation of a dark-colored, wave-length selective oxide film on aluminum
US4421612A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 29, 1981 |
| Grant date | Dec 20, 1983 |
| Priority date | — |
| Expiry date | Jun 29, 2001 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S126/908
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
A dark-colored, wave-length selective oxide film on aluminum is prepared thereby that the metal subsequent to a cleaning treatment is submerged into a bath consisting of an aqueous solution having pH 8.9-10.9 and at a temperature of from 20.degree. to 100.degree. C. under conditions which result in an electrode potential of between -1.1 and -0.6 volt relative to a saturated calomel electrode. The said potential can advantageously be maintained by either addition of H.sub.2 O.sub.2 to the bath or by electric polarization. In a more specific embodiment of the process there is used an aqueous solution of 1-100 g NH.sub.4 Cl or (NH.sub.4).sub.2 SO.sub.4 per liter solution with or without addition of aluminate ions AlO.sub.2 -- or Ca.sup.++, the pH of the solution, if necessary, being adjusted to pH 9 by addition of NH.sub.3, NaOH, KOH, Ca(OH).sub.2 and that the content of silicon, chromium and phosphorus each is maintained under 10 ppm.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.