Source: http://www.google.com/patents/US4756771?dq=5,966,702
Timestamp: 2014-07-10 02:58:24
Document Index: 178192625

Matched Legal Cases: ['application No. 50', 'application No. 2', 'application No. 33', 'application No. 2', 'application No. 34', 'application No. 25']

Patent US4756771 - Colorless sealing layers for anodized aluminum surfaces - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsA process and composition for producing colorless, cold-sealed, anodized aluminum or aluminum alloy surfaces. The composition comprises an aqueous solution containing nickel ions and a solution of at least one azo or azo metal dye, the colors imparted by the nickel ions and dye offsetting each other...http://www.google.com/patents/US4756771?utm_source=gb-gplus-sharePatent US4756771 - Colorless sealing layers for anodized aluminum surfacesAdvanced Patent SearchPublication numberUS4756771 APublication typeGrantApplication numberUS 07/038,480Publication dateJul 12, 1988Filing dateApr 14, 1987Priority dateJan 3, 1985Fee statusPaidAlso published asCA1268604A1, DE3500079A1, EP0186897A1, EP0186897B1Publication number038480, 07038480, US 4756771 A, US 4756771A, US-A-4756771, US4756771 A, US4756771AInventorsDieter Brodalla, Winfried Kirchhoff, Hans J. GoehausenOriginal AssigneeHenkel Kommanditgesellschaft Auf AktienExport CitationBiBTeX, EndNote, RefManPatent Citations (9), Non-Patent Citations (5), Referenced by (62), Classifications (8), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetColorless sealing layers for anodized aluminum surfacesUS 4756771 AAbstract A process and composition for producing colorless, cold-sealed, anodized aluminum or aluminum alloy surfaces. The composition comprises an aqueous solution containing nickel ions and a solution of at least one azo or azo metal dye, the colors imparted by the nickel ions and dye offsetting each other.
We claim: 1. A process for producing colorless, cold-sealed, anodized aluminum or aluminum alloy surfaces comprising the treatment of said surfaces at a temperature of about 15�-70� C. with(A) an aqueous solution consisting essentially of nickel ions, present in a sealingly effective amount and (B) an aqueous solution consisting essentially of at least one organic dye present in an amount effective to offset any color imparted to said surface by said nickel ions which(a) has an absorption maximum of about from 450 to 600 nm; (b) has an extinction coefficient of at least 103 liter/mol cm; (c) is capable of being dissolved to form a molecular dispersion; and (d) does not undergo a precipitation reaction with nickel ions or the other components of the solution at the treatment solution concentrations wherein said solutions are used simultaneously or in any sequence. 2. The process of claim 1 wherein step (A) preceeds step (B).
6. The process of claim 1 wherein said at least one dye has an extinction coefficient of about from 5�103 to 5�105 liter/mol cm.
7. The process of claim 5 wherein said at least one dye has an extinction coefficient of about from 5�103 to 5�105 liter/mol cm.
19. The process of claim 18 wherein said treatment is conducted at a temperature of about 20� to 40� C.
20. The process of claim 18 wherein said treatment is conducted at a temperature of about 25� to 32� C.
23. The process of claim 1 wherein said treatment is conducted at a temperature of about 25� to 32� C. and at a pH of about 5.5 to 6.5.
26. The process of claim 4 wherein: said at least one dye consists essentially of a combination of aluminum red GLW and aluminum violet CLW, said combination being present in about 1 to 2.9 mg/l; said nickel ions are present in an amount effective to seal said surfaces; the temperature of said treatment is at about 25� to 32� C.; and the pH of said combined solutions is about 5.5 to 6.5.
29. The composition of claim 27 wherein said at least one organic dye has an extinction coefficient of about 5�103 to 5�105 liter/mol cm.
In contrast to "hot sealing", in which the pores of anodized aluminum surfaces are closed and rendered corrosion resistant by treatment with water, steam, or metal salt solutions at a temperature above 90� C., in the art the terms "cold sealing" or "cold impregnation" or "low temperature sealing" are generally understood to denote processes by which the porosity of anodized aluminum surfaces is reduced at a temperature of 15� C. to 70� C., and the surface properties thereof are substantially improved. These processes are intended to provide improved corrosion resistance over that of unsealed surfaces.
Processes to effect cold sealing of anodized work pieces made of aluminum and alloys thereof are known in the prior art. Thus, Chemical Abstracts, 87, 75493t (1977) describes employing solutions of various metal fluorides, for example CrF3, MnF2, CoF2 or NiF2, for treating anodized aluminum surfaces at from room temperature to 50� C. Published Japanese patent application No. 50-117,648 describes the sealing of anodized aluminum surfaces by immersion into an acid solution containing a metal (such as nickel) fluoride and isoamyl alcohol at 30� C.
Published British patent application No. 2,137,657 (and corresponding German patent application No. 33 01 507) also describe a process for cold sealing of aluminum or aluminum alloy surfaces in which process solutions containing fluorine or fluoride or complex fluoride anions (such as nickel fluoride and/or cobalt fluoride) are employed at temperatures of 25� to 60� C. Similarly, published U.K. patent application No. 2,140,033 (and corresponding published German patent application No. 34 11 678) disclose a process for after-sealing of aluminum and aluminum alloys subsequent to electrolytic anodization wherein nonionic surfactants capable of reducing the surface tension of the sealant bath are added to aqueous solutions containing at least one nickel salt. Useful nonionic surfactants include fluorocarboxylates and organosiloxanes.
Processes for removing or eliminating undesired colorations or discolorations of anodized surfaces of certain aluminum alloys have been described in U.S. Pat. No. 3,874,902 (and corresponding published German patent application No. 25 10 246). In the process disclosed, alterations of the color of aluminum surfaces resulting from alien metals of the aluminum alloys, e.g. copper, are eliminated by adding a monoazo dye to the bath at a temperature which must be maintained at about 180�-210� F. (82�-98� C.) and at a pH which must be between about 5.5 and 6.5, for a time of 10-30 minutes. However, the disclosure teaches removing only those discolorations which have been formed from nonaluminum components of the aluminum alloy in the anodization step preceding the sealing. As treatment accelerators there can be added metal salts, such as cobalt or nickel salts. However, the addition of accelerators renders the color control difficult.
DESCRIPTION OF THE INVENTION The present invention provides a process for the cold sealing of anodized aluminum surfaces in which (in spite of the use of aqueous solutions containing nickel salts) colorless layers can be produced and the greenish coloration imparted by nickel ions to the surface layers can be avoided. Aqueous solutions of nickel fluoride absorb light in the wave length ranges of from 350 to 450 nm and from 650 to 850 nm. Now it has suprisingly been found that selected dyes having absorption maxima in the range of from 450 to 600 nm, and preferably from 490 to 560 nm, when used conjointly with aqueous solutions of nickel salts, allow the cold sealing of anodized aluminum surfaces to be accomplished without a visible occurrence of greenish colorations of the surfaces. In the cold sealing of aluminum surfaces using nickel salt solutions containing such dyes, the surfaces formed show the natural shade of aluminum.
The present invention provides compositions for producing colorless sealed layers on anodized aluminum surfaces at a temperature of 15� to 70� C. and at a pH of 5 to 7.5. The compositions contain from 1 to 5 grams of nickel cations per liter of sealing solution in the form of a water-soluble nickel salt; at least one organic dye having (a) an absorption maximum in the range of 450 to 600 mm, (b) a Beer's law extinction coefficient of at least 103 liter/mol cm, and which are (c) capable of being dissolved to form a molecular dispersion, while (d) not undergoing a precipitation reaction with the nickel ions and/or the other components of the solution at the application concentrations; and, optionally, further organic and/or inorganic auxiliary agents conventional in the cold sealing of anodized aluminum surfaces.
The present invention also provides a process for producing colorless sealed layers by treating anodized aluminum surfaces with aqueous solutions containing nickel ions and, optionally, further organic and/or inorganic auxiliary agents conventional in the cold sealing of anodized aluminum surfaces. The treatment is conducted at a temperature of 15� C. to 70� C. and pH of 5 to 7.5. The inventive process is particularly characterized by the addition (optionally continuously) of at least one organic dye as described immediately above, to the aqueous sealing solution.
(b) The dyes must have an extinction coefficient of at least 103 liter/mol cm. At a given nickel content of the sealing solution the concentration of the dyes is from 0.5 to 80 mg/l, which, however, will depend on the specific extinction of the respective dye. A high color intensity--corresponding to a high extinction coefficient--preferably in the range from 5�103 to 5�105 liter/mol cm allows the use of low dye concentrations. As preferred according to the invention concentrations of 1.0 to 10.0 mg per liter of the sealing solution are used, 1 to 2.9 mg/l being particularly preferred. Since dyes having lower color intensity will have to be employed in accordingly higher concentrations and high concentrations applied can adversely affect the quality of the sealing process, dyes having low extinction coefficients are not suitable for the invention.
In a particularly preferred embodiment of the process according to the invention there are used treatment solutions wherein the green coloration caused by the presence of nickel ions is completely offset by the red coloration caused by the presence of the dye molecules and which, thus, appear to be colorless. Thus, dyes having an extinction coefficient in the range of 5�103 to 5�105 liter/mol cm at an absorption maximum in the range of from 490 to 560 nm and at a concentration of from 1 to 10 mg/l, will decolorize sealing solutions which contain from 1 to 5 g/l of nickel.
Anodized surfaces of aluminum or its alloys are treated with the inventive dye solutions: at a temperature of 15� C. to 70� C., preferably 20� C. to 40� C., more preferably 25� C. to 32� C.; and at a pH value of 5.0 to 7.5, preferably 5.5 to 7.0, ideally 6.5. The treatment is effected by immersing the aluminum articles to be treated in the inventive solutions for 0.1 to 1.5, preferably 0.4 to 1.2, minutes per micron (μ) of layer thickness. It is desirable that the articles are subsequently rinsed with fully desalted water.
EXAMPLES The present invention is further illustrated by way of the following non-limiting examples.
______________________________________Current density      1.5 A � dm-2 ;Temperature          20� C.Layer thickness      20&#956;; andSulfuric acid content                180 g/l______________________________________
In the actual process of sealing the aluminum oxide surfaces, there were used aqueous solutions having compositions as indicated in the individual examples. The pH was between 5.5 and 6.5 and was readjusted with acetic acid when necessary. The temperature of the treatment was 28� C. to 32� C., and the duration of the treatment was 0.5 minutes per micron (μ) of layer thickness.
Example 1 (violet dye) The total starting solution contained:
Comparative Example A (no dye) Under the same conditions as in Example 1, a solution was used for sealing which contained only 7.0 g/l of NiF2.4H2 O; that is, it did not contain any dye. A comparable decrease of the absorptions as typical for nickel was observed, however the resulting surfaces showed a greenish discoloration.
Comparative Example B (dye outside inventive scope) The initial solution contained 7.0 g/l of NiF2.4H2 O and 5.0 mg/l of aluminum copper (a dye outside the scope of this invention). The pH value was 5.8.
Example 2 (red dye) The starting solution contained 7.0 g/l of NiF2.4H2 O and 5.0 mg/l of aluminum red GLW. The pH value was 5.8.
Example 3 (red and violet dyes combined) The starting solution contained:
Example 4 (red and violet dyes combined-with replenisher) The starting solution contained:
Example 5 (red and violet combined--with replenisher) The starting solution contained:
Examples 6 and 7 (red and violet dys combined--with replenisher) The starting solution contained:
Example 8 (red and violet dyes combined--continuous replenishment) A solution for use in cold impregnating was prepared in a bath container having a capacity of 18 m3 which solution contained 2 g/l of nickel and 1.4 g/l of fluoride. 1.25 mg/l of aluminum red GLW and 1.25 mg/l of aluminum violet CLW were added, so that upon visual inspection the solution appeared to be colorless. During a first eight week test period, aluminum articles having anodized aluminum surfaces totaling 11,500 m2 and comprising oxide layer thicknesses of from 2μ to 25μ which had been prepared under varied anodization conditions, were treated in the bath.
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