Fluoride and chromium free acid etchant rinse for aluminum
US4980076A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 6, 1989 |
| Grant date | Dec 25, 1990 |
| Priority date | — |
| Expiry date | Sep 6, 2009 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC23G1/125
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
Problems with previously known aqueous acidic rinsing solutions for aluminum after shaping while using surface lubricants are avoided by use of a solution which contains water and (A) orthophosphoric acid in an amount to give a stoichiometric equivalent of 3.0 to 50 g/L as PO.sub.4.sup.-3, (B) an aluminum ion sequestrant component in an amount of 0.01 to 10.0 g/L; and (C) 20 to 170 ppm of ferric ion. The ferric ions act to inhibit corrosion of the stainless steel process equipment. Preferably the solution also contains 0.1 to 1.0 g/L of H.sub.2 O.sub.2, NO.sub.2.sup.-1 ions, or a mixture thereof to reoxidize ferrous ions formed by reduction of ferric ions during use of the solution and thus maintain the concentration of ferric ions above 20 ppm at all times. The solution may also contain surfactant and up to 10 g/L of dissolved aluminum ions.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.