CH650276A5 - METHOD AND MEANS FOR ACIDICALLY CLEANING ALUMINUM SURFACES. - Google Patents

Description

The invention relates to the cleaning of aluminum surfaces.

In the manufacture of aluminum containers (a term that includes aluminum alloys in this specification), a drawing and shaping process is used (commonly referred to as drawing and ironing). This process leads to the separation of lubricants and formwork oils on the surfaces of the aluminum containers. In addition, remaining aluminum fines, i.e. small aluminum particles, deposited on both the inside and the outside surface. Usually, the outer surface of the container has smaller amounts of fine aluminum particles than the inner surface, since when pulling and ironing or sliding, the outer surface is not subjected to as much abrasion from the mold as the inner surface.

Before any processing steps, such as coating the coating and separating hygienic lacquers, the surfaces of the aluminum containers must be clean and free of water breakthroughs. free of contaminants that interfere with further processing and make the containers unacceptable for their use.

Means and methods for cryogenic cleaning of aluminum surfaces are disclosed in U.S. Patents 4,009,115, 4,116,853, 4,124,407 and 3,969,135. These patents disclose detergents containing sulfuric acid, hydrofluoric acid or a fluoride and a surfactant.

Agents that fall within the disclosure of these patents are commercially successful and are in fact widely used in cleaning aluminum containers (including aluminum alloys). Such commercial agents typically use a combination of two nonionic surfactants to increase cleaning performance and minimize foaming.

One of the problems with the use of conventional acidic cleaning agents is caused by the accumulation of lubricants and formwork oils used in the drawing and molding of aluminum containers when these containers are treated with the cleaning solutions. The cleaning solutions must be supplemented with fresh solutions from time to time to keep the oil content low. If the oil contents in the cleaning bath become too high, containers cleaned in the bath develop considerable water breakthroughs after rinsing off the cleaning solution. Water breakthroughs indicate that the surface of the aluminum is not clean and that there are oils or other foreign deposits. Such containers must be discarded or cleaned again since they are not suitable for further processing as containers for beverages and other foodstuffs.

It has now been found that an aqueous sulfuric acid / hydrofluoric acid cleaning agent containing a particular anionic surfactant, namely an alkali metal 2-butoxyethoxyacetate, is surprisingly advantageous.

The invention thus provides an aqueous cleaning solution for removing and dissolving aluminum fines and for cleaning aluminum surfaces from lubricating oils, which contains 1 to 10 g / 1 sulfuric acid, 0.005 to 0.1 g / 1 hydrofluoric acid and 0.1 to 10 g / 1 Contains alkali metal 2-butoxyethoxy acetate.

The invention also provides an aqueous solution concentrate for forming the aqueous cleaning solution which comprises 200 to 600 g / 1 sulfuric acid and 0.01 to 10 parts by weight of alkali metal 2-butoxyethoxyacetate per part by weight of sulfuric acid.

The invention further provides a method for cleaning an aluminum surface, in which (a) the surface is brought into contact with the aqueous cleaning solution and (b) the aluminum surface is rinsed to remove the cleaning solution.

It has been found that the cleaning solutions according to the invention tolerate relatively high concentrations of lubricants and formwork oils without any water breakthroughs occurring on the containers cleaned by such solutions. Significant savings are thus achieved since a large number of containers can be processed before the operation has to be stopped in order to supplement all or part of the cleaning solution.

Another considerable advantage of the cleaning agents according to the invention is the almost complete absence of foam in the cleaning bath and in the rinsing cycle following the cleaning step. Many of the acidic cleaning agents currently on the market offer problems with foam to a greater or lesser extent. Such agents are mixtures of a highly foaming, nonionic surfactant for educating5

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Good cleaning effect with a low-foaming anionic surfactant to try to reduce the amount of foam that otherwise occurs. Foaming often causes the foam to overflow or drip onto the bottom of the factory part that is being operated, resulting in smoothness and unsafe conditions. Also, the appearance of the foam can lead the user to conclude that the cleaning solution is unsatisfactory due to the risks of foam overflow. As a result, tank cleaning is stopped while skimming the foam or replenishing the cleaning solution, resulting in loss of time and reduced tank throughput.

Another advantage of the cleaning agents according to the invention is that the alkali metal 2-butoxyethoxyacetate can be used effectively in relatively small amounts, and this factor, combined with the low cost of this surfactant (as a sodium salt), results in comparison with nonionic surfactants currently used to large economic savings compared to the current commercial means. Considerable cost savings are achieved even if a low-foaming nonionic surfactant or a combination of such surfactants is also present in the cleaning agent according to the invention, since the nonionic surfactant (s) can also be present in relatively small amounts.

Typically, concentrates with sulfuric acid and the surfactant are manufactured by the manufacturer and sold to container processing companies that manufacture cleaning solutions by diluting such concentrates with water and adding hydrofluoric acid to the solutions. Concentrates currently on the market tend to be fairly colored due to decomposition products formed by the action of concentrated sulfuric acid on the surfactants and / or from interactions between the surfactants and contaminants in the commercially available sulfuric acid which are commonly found in the Compilation of concentrates is used. Surprisingly, concentrates formed with an alkali metal 2-butoxyethoxy acetate as the only surfactant are colorless or only pale yellow in color. Such concentrates are stable at very low temperatures, e.g. there is no precipitation even at the temperature of a dry ice / acetone bath. The concentrates are also stable and do not change color even if they are exposed to temperatures of 50 ° C for three weeks or longer. Most of the concentrates currently in use discolor even at room temperature, and some form precipitates when containers with the concentrates are placed in dry ice / acetone baths. The great stability of the agents according to the invention enables problem-free shipping and storage under adverse temperature conditions, a further considerable economic advantage.

Another advantage of the agents according to the invention is the high degree of purity generated in the containers, especially when low-foaming nonionic surfactant is also present, which leads to unusually uniform deposition of conversion coatings and paints on the containers during further processing.

Interestingly, when the only anionic surfactant disclosed in U.S. Patents 4,009,115,4 116,853 and 4,124,407, namely sodium 2-ethylhexyl sulfate (Tergitol Anionic 08), was tested in the acidic cleaners of these patents, water breakthroughs occurred on the aluminum containers cleaned with such agents after adding only small amounts of formwork oils. Thus, the surprising advantages contributed by the particular anionic surfactant according to the invention appear unique and are clearly not anionic

General advantages of surfactants.

The means and methods according to the invention lead to improvements over the means and methods as disclosed in US Pat. Nos. 4,009,115, 4,116,853 and 4,124,407, the disclosures of which are particularly incorporated by reference. The procedures and methods which are used there in the execution of cleaning processes and in the formation of concentrates and cleaning solutions are also applicable to the invention, unless stated otherwise.

The aqueous cleaning solution according to the invention comprises 1-10 g / 1, preferably 3 to 5 g / 1 sulfuric acid, 0.005 to 0.1 g / 1, preferably 0.01 to 0.03 g / 1 hydrofluoric acid and 0.1 to 10 g / 1, preferably 0.2 to 0.8 g / 1 alkali metal 2-butoxyethoxyacetate. The alkali metal 2-butoxyethoxyacetate is preferably sodium 2-butoxyethoxyacetate

O

II

[CH3 (CH2) 3OCH2CH2OCH2C-OeNa®],

it is available under the trade name "Mirawet B" (from Miranol Chemical Company, Inc.) as an aqueous solution with 49.0% sodium 2-butoxyethoxyacetate. Other alkali metal salts can be used, e.g. Potassium or lithium 2-butoxyethoxyacetate.

A preferred solution comprises 3 to 5 g / 1 sulfuric acid, 0.01 to 0.03 g / 1 hydrofluoric acid and 0.2 to 0.8 g / 1 sodium 2-butoxyethoxyacetate.

The solution according to the invention preferably contains 0.1 to 10 g / 1, preferably 0.2 to 0.8 g / 1 of the low-foaming nonionic surfactant. The surfactant can be one or a combination of two or more low foaming nonionic surfactants. A weight ratio of alkali metal 2-butoxyethoxyacetate to nonionic surfactant of about 1: 1 is advantageously used.

The term "low-foaming nonionic surfactant" means that the nonionic surfactant or a combination of nonionic surfactants produces less than 20 mm foam after standing for 5 minutes in the well-known Ross Miles foam test at 50 ° C. Examples of such low foaming nonionic surfactants that can be used alone or in combination in practicing the invention include the following:

Triton DF-16 (Rohm & Haas Co.), believed to be a modified, polyethoxylated, straight chain alcohol;

Polytergent S-505 LF (Olin Corp.), believed to be a modified, polyethoxylated, straight chain alcohol;

Surfonic LF-17 (Jefferson Chemical Co.), believed to be an alkyl polyethoxylated ether;

Antarox BL 330 (GAF Corp.), believed to be an alkyl poly (ethylene oxide) ethanol;

Triton CF-10 (Rohm & Haas Co.), believed to be an alkylaryl polyether with a carbon chain of about 14 carbon atoms and about 16 moles of ethoxylation;

Pluronic L061 (BASF Wyandotte, Inc.), believed to be a condensate containing only ethylene oxide and propylene oxide chains;

Antarox LF-330 (GAF Corp.), believed to be an alkyl poly (ethylene oxide) ethanol; and

Min-Foam IX (Union Carbide Corp.), believed to be an alkyloxy (polyethyleneoxypropyleneoxyisopropanol) with a molecular weight of approximately 706.

The pH of the cleaning agents according to the invention is usually 0.6 to 2.0. It is preferably kept in the range of 1.0 to 1.8 and most preferably in the range of 1.2 to 1.5.

The concentrates according to the invention comprise 200 to

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600 g / 1 sulfuric acid and 0.01 to 10 parts, preferably 0.04 to 0.27 parts, of alkali metal 2-butoxyethoxyacetate per part of sulfuric acid. Parts refer to weight in this description. A suitable amount of alkali metal 2-butoxyethoxyacetate in a particular concentrate can be determined using these ratios and the amount of sulfuric acid desired in the cleaning solution so that the desired amount of alkali metal 2-butoxyethoxyacetate is present in the cleaning solution when the concentrate is included an appropriate amount of water. If e.g. 1 g / 1 sulfuric acid is desired in the cleaning solution, 0.1 g to 10 g of alkali metal 2-butoxy-ethoxyacetate are present in the concentrate per g of sulfuric acid; and if 10 g / 1 sulfuric acid is desired in the cleaning solution, 0.1 g to 1 g alkali metal 2-butoxy-ethoxyacetate is present in the concentrate per g sulfuric acid.

Optionally, 0.01 to 10 parts, preferably 0.04 to 0.27 parts, of low-foaming nonionic surfactant are also present in the concentrate.

The concentrate according to the invention can be added to water in controlled amounts, sufficient for producing a cleaning solution with the desired concentrations of sulfuric acid and alkali metal 2-butoxy-ethoxyacetate. Hydrofluoric acid is usually added separately in amounts sufficient for the desired concentration. While the hydrofluoric acid can be added to the concentrate in amounts sufficient for the required amounts in the cleaning solution when the concentrate is added to water, it is very preferred to add the hydrofluoric acid to the cleaning solution in carefully measured amounts on a continuously controlled basis. Separately recorded addition of the hydrofluoric acid is preferred because the cleaning solution continuously loses hydrofluoric acid since the aluminum surfaces are etched during the cleaning stage.

The surface of the aluminum (including aluminum alloys) to be cleaned with the aqueous cleaning agent of the invention can be contacted with the solution by any contact technique known in the art, e.g. by conventional spraying or immersion. The temperature of the detergent is usually at least 32 ° C (90 ° F). It is preferably kept in the range of 46 to 63 ° C (115 to 145 ° F) for maximum cleaning effect. Treatment times with the cleaning solutions are usually in the range of 15 s to 2 min. Desirably, the hydrofluoric acid content of the cleaning solution and the contact time with the aluminum surface are adjusted so that there is an aluminum dissolution of 90 to 280 mg, preferably 100 to 220 mg / m2 (8 to 25 mg, preferably 9 to 20 mg / ft2) of treated aluminum surface. For example, the amount of hydrofluoric acid in the cleaning solution is preferably such that the aluminum dissolution rate is 90 to 280 mg / m2 (8 to 25 mg / ft2) of treated aluminum surface at a temperature of 54 ° C (130 ° F) and a contact time of 1 min is. Aluminum cans are preferably treated by the process according to the invention.

The invention is further illustrated by the following examples, in which said alloy 3004 is the conventional aluminum alloy known under this name, which contains about 1.2% by weight of manganese and 1.0% by weight of magnesium, the balance being aluminum and normal Impurities.

example 1

1 1 concentrate was prepared containing the following amounts of ingredients:

per 1

H2SO4 (specific weight 1.84 or 66 ° Baumé) 467.2 g (256 ml)

H20 709.6 g (711 ml)

MirawetB 88.6 g (80 ml)

The concentrate was clear and practically colorless. 60.0 ml of the concentrate was added to 5.940 l of water to form 6 l of solution, the 4.67 g / l H2S04 (specific weight 1.84 or 66 ° Baumé) and 0.434 g / l sodium-2 -butoxyethoxyacetate (0.886 g / 1 Mirawet B) contains. 20 ppm of hydrofluoric acid was added to form a cleaning solution and this was stirred to make its composition uniform.

3004 alloy cans drawn into one-piece containers were used in this procedure. The cans were covered with fine aluminum particles and drawing oils.

Test samples were treated as follows:

a) sprayed with the above cleaning solution kept at 54 ° C (130 ° F) for 1 min,

b) rinsed with water by immersion in cold water for 30 s,

c) left for 30 s, then examined for water breakthroughs inside and outside and d) wiped the inside with a clean, white cloth and checked for fine aluminum particles.

A can was tested as above and the results recorded. Then 5 ml of a cooling oil emulsion as used by Reynolds Aluminum Company in drawing and forming aluminum cans was added to the cleaning solution and another can was tested and the results recorded. Another 5 ml of cooling oil was then added to the bath and another can was tested and the results recorded. Another 5 ml aliquots of cooling oil were added and a can was tested after each addition until water breakthroughs were obtained. After each addition of cooling oil, the amount of foam in the bath was determined.

The results of these tests are shown in Table I below:

Table I

Addition of cooling

Extent of

aluminum

foam

oil emulsion

Water penetration in the bathroom

on the cloth

0

no no no

5 ml none none very low:

10 ml none none very low

15 ml none none very low

20 ml none none very low

25 ml none none very low

30 ml low no very low

* "Very low" means no more than 0.6 cm (W) foam Example 2

61 cleaning solutions were prepared by adding 28.02 g of H2S04 (specific weight 1.84 or 66 ° Baumé), 1.30 g of sodium 2-butoxyethoxyacetate and 20 ppm of hydrofluoric acid to water. This cleaning solution contains 4.67 g / 1 H2S04 (specific weight 1.84 or 66 ° Baumé) and 0.217 g / 1 sodium 2-butoxy-ethoxyacetate (i.e. half the amount of the cleaning solution of Example 1).

Aluminum cans from the same approach as in Example 1 were tested according to the conditions and procedures given in Example 1 with the following results:

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Table II

Add cooling dimension of the aluminum foam oil emulsion. Water breakthrough fractions in the bath on the towel

0.

no no no

5 ml none none very low '

10 ml none none very low

15 ml none none very low

20 ml none none very low

25 ml none none very low

30 ml low no very low

* "Very low" means no more than 0.6 cm (Vi ") foam

Comparative Example 3

61 of an aqueous cleaning solution were prepared containing the following amounts of ingredients per 1:

H2SO4 (specific weight 1.84 or 66 ° Baumé) sodium atrium-2-ethylhexyl sulfate

HF

4.67 g 0.464 g

(0.98 ml Tergitol Anionic 08) 20 ppm

Aluminum cans from the same approach as that of Example 1 were tested according to the conditions and procedures given in Example 1 with the following results:

Table III

Addition of cooling

Extent of

aluminum

foam

oil emulsion

Water penetration in the bathroom

on the cloth

0

low none none

5 ml spread *

no no

10 ml does not spread any

H2S04 (specific weight 1.84 or 66 ° Baumé) 4.70 g ethoxylated abietic acid (Hercules

Surfactant AR 150) * 1.053 g alkyl poly (ethyleneoxy) ethanol (Antarox

5 LF-330) * 0.673 g

HF 20 ppm

* both non-ionic surfactants

10 aluminum cans from the same batch as that of Example 1 were treated according to the procedures and conditions of Example 1 with the following results:

Table V

* "Widespread" means commercially unacceptable

Comparative Example 4

61 of an aqueous cleaning solution were prepared with the ingredient amounts given in Example 3, except that 0.928 g / l of sodium 2-ethylhexyl sulfate was used. Test procedures were carried out as in Example 3 with the following results:

Table IV

45

50

Addition of cooling

Extent of

aluminum

foam

55

oil emulsion

Water flow

Fine particles in the bathroom

breaks on the cloth

0

low none none

5 ml spread *

no no

60

10 ml does not spread any

* "Widespread" means commercially unacceptable

Comparative Example 5

61 of an aqueous detergent were made with the following ingredient amounts per 1:

Addition of cooling

Extent of

Aluminum-

foam

oil emulsion

Water penetration in the bathroom

on the cloth

0

no

Slight trace **

5 ml low

Slight trace

10 ml spread *

Slight trace

* "Widespread" means commercially unacceptable 25 ** "low" means between 0.6 QA ") and 2.5 cm (1")

Comparative Example 6

61 of an aqueous cleaning solution were prepared with the following ingredient amounts per 1:

30th

H2SO4 (specific weight 1.84 or 66 ° Baumé) 4.67 g modified polyethoxylated straight-chain alcohol (Triton DF-16)

(nonionic surfactant) 0.464 g

35 HF 20 ppm

Aluminum cans from the same batch as that of Example 1 were treated according to the procedures and conditions of Example 1 with the following results:

Addition of cooling

Extent of

aluminum

foam

oil emulsion

Water flow

Fine particles in the bathroom

breaks on the cloth

0

no

Slight trace *

5 ml none

Slight trace

10 ml none

Slight trace

15 ml none

Slight trace

20 ml none

Slight trace

25ml low

Slight trace

* "Low" means between 0.6 cm and 2.5 cm (0.25 and 1 ")

Example 7A and Comparative Examples 7B, 7C and 7D The following concentrates were prepared:

h2s04 (specific weight 1.84 or 66 ° Baumé) h20

Sodium-2-butoxyethoxyacetate B

h2s04 (specific weight 1.84 or 66 ° Baumé) h20

Sodium 2-ethylhexyl sulfate C

h2s04 (specific weight 1.84 or 66 ° Baumé)

h2o per 1 467.2 g 709.6 g 43.4 g

467.2 g 709.6 g 46.4 g

469.6 g 627.0 g

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ethoxylated abietic acid (Hercules

Surfactant AR 150) 105.3 g alkyl poly (ethyleneoxy) ethanol (Antarox

LF-330) 67.3 g D

H2S04 (specific weight 1.84 or 66 ° Baumé) 467.2 g

H20 709.6 g Modified polyethoxylated straight chain alcohol (Triton DF-16) 46.4

Samples of the above concentrates were treated according to the conditions shown in Table VII below and with the results also given:

Table VII

Concentrate

Dry ice / acetone

0 ° C, 24'h

55 ° C, 24 h occurred

bath

A

somewhat viscous,

clear

clear, practical

clear, practically practically colorless solution

colorless solution colorless solution

B *

-

-

-

C.

speak considerable considerable very much speak

Precipitation

Precipitation dark brown discoloration, some separation of layers

D

somewhat viscous,

light brown moderately brown

light brown colored colored solution

solution

solution

* A homogeneous solution could not be obtained. Tergitol 08 as a layer over the sulfuric acid solution.

Concentrate A was then placed in an oven kept at 50 ° C for 3 weeks. When the solution was removed, it was clear and practically colorless, i.e. no color change had occurred during this time.

Example 8

61 of an aqueous cleaning solution were prepared with the following constituent amounts per 1:

H2S04 (specific weight 1.84 or 66 ° Baumé) 4.7 g Mirawet B 0.9 g

HF 20 ppm

Aluminum cans made of 3004 alloy, drawn into one-piece containers, were used in this procedure. The cans were covered with fine aluminum particles and drawing oils.

Test samples were treated as follows:

a) sprayed with the above cleaning solution kept at 53 ° C (125 ° F);

b) rinsed with water by immersion in cold water for 30 s and c) left for 30 s, after which they were examined for water breakthroughs both inside and outside.

A can was tested as above with a spraying time in stage a) of 30 s and the results recorded. A second can was tested as above with a spraying time in step a) of 45 s and the results recorded. Then 200 ppm Nalco XL 174 (a mineral oil-based coolant and lubricant for pulling and ironing aluminum cans) were added to the cleaning solution and a third can as above with a spraying time in stage a) of 30 s and a fourth can with a spraying time in stage a ) tested for 45 s.

The results of these tests are shown in Table VIII:

Table VIII

Addition of Nalco XL 174, TpM

Spraying time in s

Extent of

Water breakthrough

gene

0

30th

no

0

45

no

200

30th

no

200

45

no

Comparative Example 9

61 cleaning solutions were added to water by adding 4.7 g / 1 H2S04 (specific weight 1.84 or 66 ° Baumé), 1.053 g / 1 Hercules Surfactant AR-150.0.673 g / 1 Surfonic LF 17 and 20 ppm hydrofluoric acid produced.

Aluminum cans from the same batch as in Example 8 were tested according to the conditions and procedures of Example 8 with the following results:

Table IX

Addition of Nalco XL 174, TpM

Spraying time in s

Extent of water breakthroughs

0

30th

no

0

45

no

200

30th

spread

200

45

low

Example 10

61 of an aqueous cleaning solution heavily contaminated with Nalco XL 174 were prepared with the following ingredient amounts per 1:

H2S04 (specific weight 1.84 or 66 ° Baumé) 4.7 g Mirawet B 0.9 g

HF 20 ppm

Nalco XL 174 500 TpM

Aluminum cans made of 3004 alloy, drawn into one-piece containers, were used in this procedure. The cans were covered with fine aluminum particles and drawing oils.

Test samples were treated as follows:

a) washed with tap water at 53 ° C (125 ° F) for 30 s;

b) sprayed with the above cleaning solution kept at 53 ° C (125 ° F) for 40 s;

c) rinsed by spraying with tap water for 20 s;

d) rinsed by spraying with deionized water and e) left for 30 s, after which they were examined for water breakthroughs both inside and outside.

A can was tested as described above and the results recorded. Then 0.9 g / l of the low-foaming non-ionic surfactant Plurafac RA 30 was added to a portion of the cleaning solution contaminated as mentioned above and a further can was tested as described above. This procedure was repeated with the addition of 0.9 g / l of the various low-foaming nonionic surfactants from the following table to fresh portions of the cleaning solution contaminated as mentioned above. The results obtained are shown in Table X below.

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Table X

Addition of 0.9 g / 1 non-ionic amount of the surfactant

Plurafac RA 30

low

Triton DF 16

no

Surfonic LF 7

no

Surfonic LF 17

no

Antarox LF 330

moderate

As can be seen from this example, the presence of a small amount of a low-foaming nonionic surfactant in addition to the alkali metal 2-butoxy-ethoxyacetate considerably increases the cleaning ability of the agent, even if there are very strong impurities in a commercially used coolant in the agent according to the invention.

G

Claims (10)

650 276 2nd PATENT CLAIMS 1. Aqueous cleaning solution for removing and dissolving fine aluminum particles and cleaning the aluminum surfaces of lubricating oils, sulfuric acid, hydrofluoric acid and a surfactant, characterized in that the solution comprises 1 to 10 g / 1 sulfuric acid, 0.005 to 0.1 g / 1 hydrofluoric acid and 0 , 1 to 10 g / 1 alkali metal-2-butoxyethoxyacetate. 2. Solution according to claim 1, characterized in that the alkali metal is I-2-butoxyethoxyacetate is sodium 2-butoxyethoxyacetate and is present in an amount of 0.2 to 0.8 g / l. 3. Solution according to claim 1 or 2, characterized in that the pH is 1.0 to 1.8. 4. Solution according to one of claims 1 to 3, characterized in that the sulfuric acid is present in an amount of 3 to 5 g / 1 and the hydrofluoric acid in an amount of 0.01 to 0.03 g / 1. 5. Solution according to one of the preceding claims, characterized in that the hydrofluoric acid is present in such an amount that the solution has an aluminum dissolution rate of 90 to 280 mg / m2 of treated aluminum surface at a temperature of 54 ° C and a contact time of 1 min. 6. Aqueous solution concentrate for forming the aqueous cleaning solution according to one of the preceding claims, characterized in that the concentrate has 200 to 600 g / 1 sulfuric acid and 0.01 to 10 parts by weight of alkali metal 2-butoxyethoxyacetate per part by weight of sulfuric acid. 7. Concentrate according to claim 6, characterized in that the alkali metal 2-butoxyethoxyacetate is sodium 2-butoxyethoxyacetate and this is present in 0.04 to 0.27 parts by weight per part by weight of sulfuric acid. 8. A method for cleaning an aluminum surface by (a) bringing the surface together with an aqueous cleaning solution containing sulfuric acid, hydrofluoric acid and a surfactant and (b) rinsing the aluminum surface to remove the cleaning solution, characterized in that the solution according to one of the claims is used as the cleaning solution 1 to 5 is used. 9. The method according to claim 8, characterized in that the solution is kept at 46 to 63 ° C. 10. The method according to any one of claims 8 or 9, characterized in that 90 to 280 mg of aluminum are dissolved per m2 of surface.