US2942956A

US2942956A - Aluminum brightener compositions

Info

Publication number: US2942956A
Application number: US766721A
Authority: US
Inventors: Daniel R Kelly
Original assignee: Wyandotte Chemicals Corp
Current assignee: Wyandotte Chemicals Corp
Priority date: 1958-10-13
Filing date: 1958-10-13
Publication date: 1960-06-28
Anticipated expiration: 1977-06-28

Description

United States Patent ALUMINUM BRIGHTENER COMPOSITIONS Daniel R. Kell Wyandotte, Mich., assign'or to Wyandotte Chemicals Corporation, Wyandotte, Mich., a corporation of Michigan No Drawing. Filed Oct. 13, 1958, Ser. No. 766,721 18 Claims. (Cl. 4142) This invention relates to ways and means for brightening aluminum surfaces of articles such as the wings of aircraft. More particularly, it relates to aluminum brightener compositions based on methylcellulose as a thickener.

In the manufacture and use of articles'h'aving aluminum surfaces (including aluminum alloy surfaces), such as those found, for example, on aircraft, such surfaces become discolored, tarnished and covered with corrosion and oxidation products. For at least aesthetic reasons, it is desirable in many cases to remove such tarnish and corrosion products and discoloration, and otherwise brighten the surface of the aluminum article. A less obvious reason for removing such products of corrosion and oxidation resides in the fact that frequently cleaned aluminum surfaces tend to last longer than infrequently cleaned aluminum surfaces, or, to state it another way, in the fact that corrosion tends to beget corrosion. Consequently, the removal of corrosion products from aluminum articles upon completion of manufacturing operations has become a standard finishing step and the 2,942,955 Patented June 28, 1960 ice long distances from the point of use from supplying these solutions at reasonable prices to users. Moreover, because the storage life of such solutions is limited, users are not able to purchase such solutions in large quantities. Consequently, up to the time of this invention, it has been customary to prepare the solution only in such quantities as will be used immediately and to do so at or near the place of use.

The aluminum brightener solutions developed heretofore by the art also suffer from another deficiency in that they are corrosive to magnesium and magnesium In many instances, the removal of corrosion products however, it is unwieldy and impractical to dip or immerse the same into baths. Accordingly, it is customary in the aircraft industry to brush orspray the brightener solution on the aluminum surfaces to be brightened and, when the desired degree of brightening has occurred,

prevent run-off and subsequent streaking of vertically disposed surfaces, the brightener solution under these conditions usually comprises a thickening agent, such as methylcellulose, in sufficient concentration to make the solution sufliciently viscous (about 80 to about 200 centipoises at 25 C.) and uniformly adherent to the surface to be brightened.

However, such solutions (particularly those containing methylcellulose as the thickening agent) as have been developed by the art suiferfrom a major deficiency. They cannot be mass-produced in large quantities and shipped long distances to various points of use nor can they be stored for much more than 1 month for the reason that, as heretofore formulated, the solutions rapidly lose viscosity. This loss in viscosity can be compensated for by initially formulating the solution with a sufliciently higher concentration of thickening agent so that, even though degradation takes place, the solution will have the desired viscosity. at a predetermined time of use. However, the raw material cost of such a solution is sufficiently great as to discourage formulators at V to rinse the solution from the brightened surface. To

alloys. There is a tendency more and more for aircraft to be constructed of both aluminum and magnesium parts. Consequently, this problem of corrosion of magnesium surfaces is becoming quite serious. Indeed, the US. Air Force in Technical Order, No. 1-l-lC-Cleaning of Aeronautical Equipmen has stated that All known brightener agents contain chemicals which attack magnesium and therefore the use of brighteners on aircraft using magnesium necessarily must be curtailed.

Still another deficiency of the prior art aluminum brighteners resides in the fact that they are all in aqueous solution form. Elimination of water from the composit-ion until the time of use would result in savings in shipping and handling costs. Elimination of the water does not, however, solve the problem of excessive loss in viscosity nor does it eliminate the liquid form of the brightener since'the strong acids which make up the prior art compositions are liquid at the usual temperature of shipping and storage. Furthermore, I have found that substitution of the strong, liquid acids by water-soluble,

solid acids of equal strength or by solid, hydrolyzable acid salts that will produce. acids of equal strength in aqueous solution does not prevent excessive degradation of the methylcellulose in the solid formulation and resultant low viscosity of the aqueous solution prepared at the time and place of use.

'It is therefore a general object of this invention to provide the art with a dry aluminum brightener composition comprising methylcellulose, which, regardless of its-age, will give, upon addition of water, an aluminum brightener solution with a viscosity Within the desired range (about to about 200 centipoises at 25 C.).

It is another object of this invention to develop an aluminum brightener composition which is substantially noncorrosive to magnesium and magnesium alloy surfaces.

Still another specific object of this invention is to develop an aluminum brightener composition in solid form, which, regardless of its age, can be readily dissolved in water in a given proportion and give an aqueous solution having a viscosity within the desired range, which is substantially noncorrosive to magnesium and magnesium alloy surfaces. 7

These and other objects as may appear as this specification proceeds are achieved by this invention.

' In summary, my invention comprises a dry aluminum brightener composition consisting essentially of a finely divided mixture of about it) to about 25 Weight percent of a solid, hydrolyzable, acid fluoride salt selected from the group consisting of alkali metal bifluorides, ammonium bifiuoride and sodium silicofluoride; about 20 to about 50 weight percent of a solid, water-soluble, organic acid with an ionization constant in the range of about 1X 10- to, about 2 lO about 15 to about 30 weight percent of a water-soluble methylcellulose of a viscositytype of about 400 to about 4-900 centipoises; and about 10 to about 30 weight percent of a water-soluble, acid-stable wetting agent. i

The function of the acid fluoride salt is to provide hydrofluoric acid under conditions of use. Representative acid fluoride salts are ammonium acid fluoride, so-

' COMPOSITION A Components Weight 7 Percent Ammonium acid fluoride Citric acid Methylcellulose (Viscosity type-4,000 cps.) Alkylarylpolyether alcohol (Triton X-100) or (Igepal C0630). Ammonium sulfate H H 99. 9 OOOOO The alkylarylpolyether alcohol identified in the foregoing composition as Triton X-l has already been described. The polyether identified as Igepal C0630 is an oxyto 3/1; about 0.8 to about 2 weight percent of a methylcellulose of a viscosity type of about 400 to about 4000 centipoises; and about 0.5 to about 3 weight percent of a nonionic wetting agent. Within these limits of concentration said compositions have an initial viscosity in the range of about 80 to about 3000' centpoises at 25 C., and a viscosity after 6 months from about 80 to about 1500 centipoises at 25 C., and are substantially noncorrosive to magnesium.

ethylated adduct of nonyl phenol which has an oxyethylene content of about 65 weight percent of the total molecule.

To prepare an aluminum brightener solution from Composition A, mix 5 parts by weight of Composition A with 95 parts by weight of water. This composition will be completely in solution in a few minutes, and be ready for use. Moreover, the resultant solution will have viscosity stability over a long period of time.

It has been observed that Composition A in aqueous solution at C. at 5 weight percent concentration results in a solution viscosity of approximately 200 centipoises, at 7 weight percent a solution viscosity of about 600 centipoises and at 12 Weight percent a solution viscosity of about 5 centipoises. Below the 12 weight percent concentration the acid concentration of the solu- :tion is at a safe level, whereas, above 12 weight percent, '.the acid concentration of the solution is such as to re- :sult in excessive etching of aluminum-surfaces. Keeping :in mind that the desired range of viscosities for alumi- :num brighteners under use conditions is about 80 to about 200 centipoises, it will be seen that Composition A has an inherent safety feature in that at unsafe concentrations the resultant solution is too thin to be used. This feature or property is possessed by all of the compositions of this invention.

It has also been observed that when the dry compositions of this invention are placed into aqueous solutions and stored for long periods of time, the solutions display a remarkable degree of viscosity stability.

Accordingly, this invention also involves the concept of liquid concentrates which are prepared by dissolving a solid composition, such as Composition A, in just enough water to completely solubilize'the composition. At the time or place of use the concentrate is then diluted with water until the viscosity is in the desired range of about 80 to about 200 centipoises at which dilution the proportion of solids in solution will be less than about 10 weight percent- In addition, this invention involves the concept of liquid, aluminum brightener compositions that are ready for instant use even after long periods of storage.

Such compositions (liquid concentrate and use solution) consist essentially of about 97 to about 87 parts by weight of water and in solution about 0.8 to 8.5

The concentration ranges for the various components of the liquid brightener composition are established by the same considerations as involved in the case of the dry brightener compositions. However, in the case of the liquid brightener the range of concentrations selected for the organic acid is somewhat narrower than in the case of the dry brightener. The reason for this is that above the maximum limit organic acids with an ionization constant in the higher end of the ionization constant range tend to degrade the methylcellulose in the liquid brightener over long periods of storage. On the other hand the maximum limit can be exceeded in the case of organic acids with ionization constants in the lower end of the range without accelerating the degradation of the methylcellulose. Consequently, the concentration range set forth is an optimum range generally.

COMPOSITION B Components Weight Percent Ammonium acid fluoride 1. 00 Citric a cirl 2. 00 Methylcellulose (Viscosity Type-4,000 cps.) 1. Alkylarylpolyether alcohol (Igepal 00630) 0. 93 EPE nonionic surfactant (Pluronic polyol L64) 0. 92 Water I 93. 30

The alkylarylpolyether alcohol in Composition B has already been described with reference to Composition A. The EPE nonionic surfactant in Composition B is a polyoxyethylene-polyoxypropylene-polyoxyethylene polyol in which the molecular weight of the polyoxypropylene base is in the range of about 1500 to about 1800 and the ethylene oxide content of the molecule is about 40 weight percent.

A sample ofComposition B has shown an initial viscosity of about 1750 centipoises at 25 C. To use Composition B add 1 part by weight of water to 1 part by weight of Composition B. Such a use solution gave an initial viscosity of centipoises at 25 C.

Unless otherwise indicated, all viscosity measurements reported in this specification were determined at 25 C. with a Brookfield Synchro-Lectric Viscometer, Model LVF (SN2497) using Spindle No. 2 and speeds of 30 r.p,m. ,up to a viscosity of 1000 cps. and 12 r.p.m. for viscosities over 1000 cps.

To use the aluminum brightener solutions of this'invention, the solutions in the desired range of viscosity are merely brushed or sprayed on the surface to be brightened The viscous solution remains in place and will eventually-dry in place unless removed. About 30 seconds after applying the brightener solution, brightening action as evidenced by gas formation can be observed. After about 5 to 20 minutes, depending upon the condition of the oxidized aluminum surface, the brightening composition can be removed therefrom by rinsing the surface with water under pressure from hoses, sprayers and the like.

' Phosphoric acid 6.5

Viscosity of sciatic .7 Example I This example illustrates the storage stability of the solid compositions of this invention.

A solidjfinely' divided, composition corresponding to Composition A (using Triton X-lOO nonionic) was pro:

pared and stored for approximately a month and a half at 100 Fl at normal humidity. A weight percent aqueous solution of a sample of the composition at the time of preparation gave a viscosity measurement of 180 centipoises at room temperature. A 5. weight percent aqueous solution of a sample of the composition taken at the end of the storage period gave a viscosity measurement of 130 centipoises at room temperature.

Example 11 To illustrate the viscosity stability of the solution compositions of this invention various aluminum brightener composition concentrates were prepared and viscosity measurements made. The following tabulated data was obtained.

TABLE I Weight Percent Components No. 1 No.2 No. 3 No. 4 No.5

Methylcellulose (Viscosity Type -4,000 cps.) Alkylarylpolyether alcohol (Triton X-lGO) 1. 0 1.0 EPE nonionic surfactant (Plur- 'onic nonionio L64) 1.0 1. 0

Ammonium acid fluoride V 1.0 Citric acid. r

Watch"; I"

Viscosity of fresh solution (centipoises at25 C;) 1 "2,000 2,000" '2, 000

after at 100 F. (centipoises at 25 (1.). i 700 l 105 230 345 v .975 Viscosity of solution after 30 days at 100 F. (centipoises at 25 C.) 275 35 60 620 ,pH 01 an aqueous solution with 5% by weight of formulation aiter 9 V days 0.4 2. 5 2.8 f *3 4.5

In the table it will be observed that the best viscosity stability is demonstrated 'by formulation No. 5, which is the only one within the concepts of this invention, and that the reduction of viscosity in formulation No. 5 is reasonably close to that of the controlformulation No. 1 comprising methylcellulose and no acid constituents. Just why the viscosity of the control formulation No. 1' oe- V so came reduced is not known although it is speculated that bacterial action was involved. 7 However, the data does demonstrate that the presence of the strong acids in formulatiOns Nos. 2, 3 and "4 accelerated the reduction 7 in viscosity. v

Example I II This example illustrates the utility of'the compositions of this invention. 1 a

The solution composition corresponding to formulation No.-5'-in'- Example II zwas 'diluted on a 1 to 1 weight basis with water and then applied to 3 tarnished panels of aluminum alloy (2O24-'1"-3; Alclad) which were disposed in a verticalposition. 'In-each case, after'about secends, the action of the brightener could be seen by the gassing thatoccurred atthe surface of the aluminum alloy.

' Five minutes after placing the brightener composition on V the panels, the-composition was washed oil from each of the panelsunder a stream of water and the condition of each of theexposed surfaces was observed. In eachcase,

' the exposed surface of the pa'nelwas bright, no streak marks were observed, and no evidences of white deposits f0! corrosive pitting wereto be found.

8 Example} This invention illustrates thesubstantially non-corrosive; action of the compositions of this invention on magnesium in each case, the panels were removed, rinsed, dried andweighed. The weight changes were minus 0.080'gram and minus 0.040 gram, respectively. a

Thus it can be seen that in accordance with the con-, cepts of this invention aluminum brightener compositions are obtained which not only have the property of good viscosity stability over long periods of time, but which are substantially non-corrosive to magnesium and magnesium alloys.

Example V This example illustrates the efiect of the ionization constant of the organic acid on the storage stability of the brightener compositions of this invention. It also illustrates that sodium bifiuoride may be used in place of ammonium bifiuoride in'the composition.

TABLE H Weight Percent Components No. 6 No.7 No. 8

Methylcellulose (Viscosity Type-4,000 cps.) 20 -20 Ammonium Sulfate I 40' 40 Alkylarylpolyether alcohol (Triton X-100) Y 10 7 10 Ammonium Bifluoride Sodium Bifluoride 10 Citric Acid 1 7 201.0 Sulfamlc Acid i H 20 Viscosity of 5% by weight aqueous solution of sample of formulation when first made up (cps. 190 .190 170 Viscosity of 5% by'weight aqueous solution of sample of formulation after holding for 30 days at-100 F. at normal humidity (cps.) 155' p, 150 30 Citric acid has a first hydrogen ionization constant of 8.7 10- whereas'sulfamic acid has an ionizationconstant of 1.01 -l0- It willbe observed that the sulfamic acid formulation (No. 8) is not at all stable in storage as compared to the citric acid formulations.v

" Example Vl This example illustrates theistorage stability of other organic acids having ionization constants within-the range of about 1X 10* to about 2X 10- "TABLE, III

. Weight Percent Oomponents No. 9' Noi q No.11

Methylcellulose (Viscosity T e4,ooo ops.) 2'0 20 20 Ammo i fate 40 i0 40 Amino 'i ie '10 10 l0 'Alk alcohol (Igepal CO630) .10 Y 10 10 J Glycollio "c d Citric Acii Diglycolliencii Viscosity of 5% by weiglit'aqueous solution of a sample of formulation after storage for approximately 5 Weeks at 100 F. at normal humidity 120, V 100 Glycollic acid has an ionization constant offLSZXlO,

9 citric acid has an ionization constant for the first hydrogen of 8.7 while diglycollic acid has an ionization constant for the first hydrogen of 1.1 X lO- Thus, Within the critical range of ionization constants, the solid, finely divided compositions of this invention have storage stability.

It should be understood that as this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the embodiments described in this specification are therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims, or that form their functional as well as conjointly cooperative equivalents, are therefore intended to be embraced by those claims.

Also, the term consisting essentially of as used in the definition of ingredients present in the composition or compositions claimed is intended to exclude the presence of significant amounts of other materials in such proportions as to interfere substantially with the properties and characteristics possessed by the compositions set forth while permitting the presence of other materials in such proportions as not substantially to affect adversely said properties and characteristics.

What is claimed is:

1. A finely divided composition suitable for use in aqueous solution at a concentration of about 2.8 to about 9.5 weight percent to brighten aluminum surfaces which consists essentially of (1) about 10 to about 25 weight percent of hydrolyzable acid fluoride salt selected from the group consisting of alkali metal bifluorides, arnmonium bifluoride, sodium silicofluoride and mixtures thereof; (2) about 20 to 50 weight percent of watersoluble organic acid with an ionization constant in the range of about 1X10- up to about 2 l0- (3) about to about 30 weight percent of water-soluble methylcellulose of a viscosity type of about 400 to about 4000 centipoises; and (4) about 10 to about 30 weight percent of a water-soluble, acid-stable wetting agent.

2. A composition according to claim 1 wherein said organic acid is citric acid.

3. A composition according to claim 1 wherein said organic acid is tartaric acid.

4. A composition according to claim 1 wherein said organic acid is glycollic acid.

5. A composition according to claim 1 wherein said organic acid is diglycollic acid.

6. A composition according to claim 1 wherein up to about 40 weight percent of said composition constitutes a. dispersing agent substantially free of chlorides, bromides, iodides and strong acids.

7. A composition according to claim 6 wherein said dispersing agent comprises sugar.

8. A composition according to claim 6 wherein said dispersing agent comprises urea.

9. A composition according to claim 6 wherein said dispersing agent comprises ammonium sulfate.

10. A composition suitable for use in aqueous solution at a concentration of about 5 parts by weight per 95 parts by weight of water, which consists essentially of about 10% by weight of ammonium acid fluoride, about by weight of citric acid, about 20% by weight of methylcellulose of viscosity type of about 4000 centipoises, about 10% by weight of a water-soluble, acidstable wetting agent, and about 40% by weight of ammonium sulfate.

11. An aluminum brightener composition consisting essentially of about 97 to about 87 parts by weight of water and in solution (1) about 0.8 to about 8.5 parts by weight of acidic components consisting of a hydrolyzable acid fluoride salt selected from the group consisting of alkali metal bifiuorides and ammonium bifluorides, and an organic acid with an ionization constant in the range from about 1 10- to about 2x10- and at a mol ratio to said fluoride salt in a range from about 0.5 to about 3; (2) about 0.8 to about 2 parts by weight of methylcellulose of a viscosity type of about 400 to about 4000 centipoises; and (3) about 0.5 to about 3 parts by weight of a water-soluble, acid-stable wetting agent, which composition is characterized by a viscosity in the range of about 80 to about 3000 centipoises at 25 C.

12. A composition according to claim 11 wherein said organic acid is citric acid.

13. A composition according to claim 11 wherein said organic acid is tartaric acid.

14. A composition according to claim 11 wherein said organic acid is glycollic acid.

15. A composition according to claim 11 wherein said organic acid is diglycollic acid.

16. An aluminum br-ightener concentrate suitable for use upon dilution at a 1 to 1 weight ratio with water, which consists essentially of about 93 weight percent of water and in solution (1) about one weight percent of ammonium acid fluoride; (2) about two weight percent of citric acid; (3) about two weight percent of methylcellulose of a viscosity type of about 4000 centipoises; (4) about one weight percent of an alkylarylpolyether alcohol wetting agent; and (5) about one weight percent of a polyoxyethylene-polyoxypropylene-polyoxyethylene nonionic wherein the polyoxypropylene portion of the molecule has a molecular weight in the range of about 800 to about 2500 and wherein the polyoxyethylene oxide content of the total molecule is to weight percent.

17. A method for brightening a tarnished aluminum surface in conjunction with a magnesium surface wherein the magnesium surface is not'substantially damaged, which comprises (1) applying to said surface a viscous liquid consisting essentially of about 97.2 to about 90.5 weight percent of water and in solution about 2.8 to about 9.5 weightpercent of a composition consisting essentially of about 10 to about 25 weight percent of a hydrolyzable, acid fluoride salt selected from the group consisting of alkali metal bifluoride, ammonium bifiuoride, sodium silicofluoride and mixtures thereof, about 20 to about 50 weight percent of an organic acid with an ionization constant in the range of about 1X10" to about 2 10'- about 15 to about 30 weight percent of a methylcellulose of a viscosity type of about 400 to about 4000 centipoises, and about 10 to about 30 weight percent of a water-soluble, acid-stable wetting agent, said liquid having a viscosity in the range of about 80 to about 200 centipoises at 25 C.; and (2) rinsing said solution from said surface when the tarnish on said surface has been removed therefrom.

18. A method according to claim 17 wherein the mol ratio of said organic acid to said fluoride salt is in a range of about 0.5/1 to 3/1.

References Cited in the file of this patent UNITED STATES PATENTS 2,687,346 McDonald Aug. 24, 1954

Claims

1. A FINELY DIVIDED COMPOSITION SUITABLE FOR USE IN AQUEOUS SOLUTION AT A CONCENTRATION OF ABOUT 2.8 TO ABOUT 9.5 WEIGHT PERCENT TO BRIGHTEN ALUMINUM SURFACES WHICH CONSISTS ESSENTIALLY OF (1) ABOUT 10 TO ABOUT 25 WEIGHT PERCENT OF HYDROLYZABLE ACID FLUORIDE SALT SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL BIFLUORIDES, AMMONIUM BIFLUORIDE, SODIUM SILICOFLUORIDE AND MIXTURES THEREOF, (2) ABOUT 20 TO 50 WEIGHT PERCENT OF WATERSOLUBLE ORGANIC ACID WITH AN IONIZATION CONSTANT IN THE RANGE OF ABOUT 1X10**-4 UP TO ABOUT 2X10**-3, (3) ABOUT 15 TO ABOUT 30 WEIGHT PERCENT OF WATER-SOLUBLE METHYLCELLULOSE OF A VISCOSITY TYPE OF ABOUT 400 TTO ABOUT 4000 CENTIPOISES, AND (4) ABOUT 10 ABOUT 30 WEIGHT PERCENT OF A WATER-SOLUBLE, ACID-STABLE WETTING AGENT.