Fluoride and chromium free acid etchant rinse for aluminum

Details Fluoride and chromium free acid etchant rinse for aluminum Fluoride and chromium free acid etchant rinse for aluminum

1989-09-06

1990-12-25

Lacey, David L.

Compositions

Etching or brightening compositions

Inorganic acid containing

252 792, 252136, 252142, 156665, 156903, 134 3, 134 41, C09K 1304, C09K 1306, C11D 708

Patent

active

049800760

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.

REFERENCES:
patent: 2834659 (1958-05-01), Mathre et al.
patent: 3466192 (1968-09-01), Gardner
patent: 4435223 (1984-03-01), Dollman
patent: 4707191 (1987-11-01), Martinou et al.
patent: 4851148 (1989-07-01), Yamasoe et al.
patent: 4857225 (1989-08-01), Terada et al.

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