CA1207218A

CA1207218A - Fluoride-free aluminum cleaning composition and process

Info

Publication number: CA1207218A
Application number: CA000424889A
Authority: CA
Inventors: Peter F. King
Original assignee: Parker Chemical Co
Current assignee: Henkel Corp
Priority date: 1982-04-07
Filing date: 1983-03-30
Publication date: 1986-07-08
Also published as: GB2121073A; BR8301743A; AU553134B2; GB2121073B; MX159384A; JPS58185781A; AU1278183A

Abstract

ABSTRACT OF THE DISCLOSURE

An aqueous acidic fluoride-free composition suitable for cleaning aluminum surfaces at moderate to low temperatures containing controlled, effective amounts of a surfactant or combination of surfactants, sulfate ions, phosphate ions and hydrogen ions to pro-vide a pH not in excess of about 2. The aqueous acidic cleaning composition is effective to remove residual organic contaminants as well as metallic particles or smut from the aluminum surfaces achieving a desired degree of surface etching and conditioning the surface for further treatment.

Description

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FLUORIDE-FREE ALUMINUM CLEANING
; COMPOSITION AND PROCESS

sACKGROUND OF THE INVENTION
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The present invention broadly relates to the art of cleaning aluminum surfaces and more particularly, to the cleaning of drawn and ironed aluminum container bodies of the types employed in the packaging of food-stuffs and beverages. Various aqueous acidic and alkaline cleaning compositions have herefore been used or proposed for removing residual organic lubricants and drawing agents from the aluminum surfaces in addition to any met.allic particles commonly referred to as smut produced during such forming operations in order that the container bodies or cans can be effectively processed through succeeding treating steps to impart satisfactory corrosion protection and lacquer and ink adhesion while at the same time preserving the shiny metallic aluminum appearance of the container.
Among the various aqueous cleaning composi-tions heretofore used or proposed are those described in United States Patents Nos. 3,969,135; 4,009,115 and 4,116,853. Such prior art cleaning compositions have ; employed fluoride ions as an essential or as a preferred ingredient to effect acceleration of chemical attack on the aluminum surfaces to be cleaned to effect removal of the metallic particles or smut thereon produced -)7~

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during the forming operations achieving a desired etch-ing ox the metal suX~ace employing modexate tempera-tures of about 120 to about 140F without impairing .
the bright shiny aluminum appearance thereof. While the effectiveness of fluoride ions to attack and remove - the adherent oxide film on aluminum surfaces at moder-ate cleaning temperatures provides for a substantial -j savings in energy in comparison to cleaners operating : `
at 180F or higher, the presence of fluoride ions in ,, commercial waste effluen-ts has become environmentally disfavored over recent years in many areas and there has been a continuing need for providing an aqueous clean-ing composition which is fluoride-free while retaining the beneficial cleaning characteristics of such prior art aluminum cleaning compositions. It is also impor-tant that such a fluoride-free aluminum cleaning compo-sition can commercially operate at moderate to relatively low temperatures of about 100 to about 160F to provide satisfactory cleaning within commercially acceptable time periods thereby providng substantial savings in energy costs over cleaners operating at relatively high temperatures of about 180F and higher.
The benefits and advantages of the present inVention are achieved by an improved fluoride-free aqueous acidic cleaning composition which can be effec-tively employed at moderate temperatures as low as about - 100 to about 140F and which effectively removes sur face contamination and smut from aluminum surfaces ; 2 ..

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within commercially satisfactory time periods rendering such surfaces suitable fox further treatment in accor-dance with convent,ional containeX manufacturing process-ing. The cleaner compositi,on of the present invention is further characterized as being of reasonable cost, simple control, effective performance and overcomes - environmental problems as$ociated with prior art fluoride-containing cleaning solutions.
SUMMARY OF THE INVENTION
The benefits and advantages of the present invention are achieved in accordance with the composi-tion aspec-ts whereof, by a aqueous acidic cleaning composition containing controlled effective amounts of a surfactant or combination of surfactants, sulfate ions, phosphate ions and hydrogen ions in an amount to provide an acidic pH of less than about 2. More specifically, the aqueous acidic cleaning composition contains a surfactant or combination of surfactants in an amount s of from about 0.1 up to about 30 grams per liter (g/l), a combination of phosphate ions and sulfate ions in an amount of about 2 to about 100 g/l of which about 30 percent to about 80 percent by weight comprise phosphate ions and hydrogen ions in an amount to provide a pH not in excess of about 2, and preferably prom about a. 5 to about 1.2 with a pH of about 0.8 being particularly satisfactory. on accordance with a preferred embodiment of the present invention, the surfactant comprises a 7~

combination of a hydrocarbon derivative surfactant of the general formula R~o~')noE and an abietic acid de-rivative surfactant having the general formula ARC H in substantially equal amounts in accordance with the description as set forth in United States Patent 3,969,135 which is assigned to the assignee of the present invention.
The aqueous acidic cleaning composition can .~
readily be prepared and replenished employing a concen-trated solution of the active constituents as herein-above set forth containing the surfactant or surfactants in an amount up to about 200 gel, a controlled combina-tion of phosphate ions and sulfate ions in an amount up to about 500 g/l and hydrogen ions to provide a pH
of less than about 0.
In accordance with the process aspects of the present invention, aluminum surfaces to be cleaned are contacted with the aqueous acidic cleaning composition at toe normal operating strength at temperatures preferably from about 110 to about 140F for energy conservation considerations and for time periods of from about 10 seconds up about 5 minutes or longer with time periods of less than about 2 minutes normally being sufficient. While the aqueous cleaning solution can also be applied by immersion and flooding techniques, it is usually preferred, in view of the configuration :`
of aluminum container bodies, to apply the cleaning solution and subsequent rinse and treating solutions by conventional spray application.
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Additional benefits and advantages of the present invention will become apparent upon a reading of the description of the preferred embodiments taken in conjunction with the specific examples provided.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
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The manufacturing sequence for producing aluminum container bodies or cans conventionally com-prises providing an aluminum strip which passes througha cupping press which forms a preliminary cup-shaped disc which is transferred to a draw and ironing press producing an elongated cup shaped body. During the cupping press and draw and ironing operation, various ; organic lubricants as well as coolants including water or dilute aqueous emulsions are applied to the surfaces of the part to facilitate the forming operations. The container bodies or cans thereafter are transferred to a trimmer in which the upper edge is trimmed whereafter the trimmed can passes through a washer containing a plurality of cleaning, rinsing and treatment stages.
At the conclusion of the washing and treating cycle, the treated cans are transferred to a dry-off oven and ` 25 the interior and exterior surfaces of the can are sub-jected to one or a plurality of lacquering steps and 72~
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exterior decorative printing steps. Typically, the exterior surface of the can is first provided with a ., decorative ink printing of suitable indicia which after drying is followed by a conventional exterior can lac-quer coating and a curing of the coating by heating to an elevated temperature such as about ~00F for a period of about 10 minutes in a recirculating air oven. After ' cooling, the interior can lacquer coating is applied to the interior surfaces of the can and the lacquer come ` 10 prises any of the types conventionally employed which are selected so as to chemically resist the foodstuff or beverages to be placed wi.thin the can in a subsequent willing station. The interior lacquer coating is again cured at an elevated temperature and the can may further optionally be subjected to a second exterior lacquer coating followed by an additional curing step before transfer to the filling station.
In many instances, the filled cans after ,.~ sealing are subjected to a pasteurization treatment in order to destroy bacteria. Such pasteurization treat-` ment typically comprises immersing the filled and sealed cans in water heated to about 150 to about 16~F for a period of about 30 minutes. Such a pasteurization treatment does not effect the over-varnished side walls of the can but unvarnished exterior bottom of the con-tainer has in many instances undergone discoloration : during pasteurization which is highly objectionable.

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In order to assure excellent ~ualit~ and durability ox such decorated, yarnished and filled cans during processing, shipment, storage and ultimate end use not only with respect to appearance but also with S respect to durability, various tests have been devised for measuring adhesion ox the lacquer coating to the can surfaces, resistance to corrosion when subjected to . high humidity at elevated temperatures, corrosion re-sistance of the can surfaces and discoloration of the varnished ana unvarnished exterior surfaces under various conditions. It is apparent that the cleaning of the can surfaces to remove the contaminating sub-stances thereon rendering the surfaces susceptible Eor further treatment and lacquering comprises an impor-tant lS step in the manuEacturing sequence and insuring that the cleaned can surfaces are receptive to such post treatments. Typically, the trimmed can body from the trimming operation enters the multiple stage washer in which after pre-washing, the can body is exposed to the cleaner of the present inVention which is applied such as by spray application for a period of about 1 minute at a temperature preferably ranging from about 110 to about 140F whereafter the cleaned çan is spray water rinsed at about 120F for a period of about 15 seconds. There-after the cleaned and rinsed can body is subjected to a treatment of any of the Various types known in the art to improve the surface characteristics thereof and 72~

to enhance corrosion resistance and other desirable properties wherea~ter the treated can is again spray water rinsed at about 120F followed by a 15 second deionized water spray rinse normally at room temprature (70 - 80F) whereafter the can is dried in a hot air recirculating oven usually at about 380 to about 400F
for a period of 5 minutes. After cooling, the can thereafter is decorated and lacquered as previously described.
It has been discovered that effective clean-ing and preconditioning of the aluminum can surface can be obtained in the absence of any fluoride ion activat-ing agents in the cleaner in accordance with the com-position of the present invention ale aqueous acidic cleaning composition in accordance with the present invention contains a surfactant or combination of sur-factants present in an amount of about 0.1 to about 30 g/l with amounts of about 0.5 to about 10 g/l being pre-ferred. The particular type of surfactant or combina-tion oE surfactants employed will depend to some extenton the types of organic and inorganic contaminants present on the can surfaces to be cleaned and can be adjusted to provide optimum removal of such soils.
The surface active agents which can be satis-factorily employed can be anionic, cationic or nonionic.
Typical examples of such surfactants are: T~RGITOL
ANIONIC - 08 (trade mark, Union Carbide Corporation) an ~7 72~8 anionic surfactant believed to be sodium 2-ethyl hexyl sulfate, '~RITO~ DF-16 (trade mark; Rohm & Haas Co.) a nonionic surfactant believed to be a modified poly-ethoxylated straight chain alcohol, POLYTERGE~T S-505 LF (trade mark, olin Corp.) a nonion:ic surfactant believed to be a modified polyethoxylated straight chain alcohol; SURFONIC LF-17 (trade mark, Jefferson Chemical Co.) a nonionic surfactant believed to be an alkyl polyethoxylated ether, PLURA~AC RA-30 (trade mark, BASF Wyandotte Corp.) a nonionic surfactant, believed to be a modified oxyethylated straight chain alcohol, TRITO~ X-102 (trade mark, Rohm & Haas Co.) a nonionic surfactant believed to be an octyl phenoxy poly ethoxy ethanol, PLURONIC L-61 (trade mark, BASF Wyandotte, Inc.) a nonionic surfactant, and believed to be a condensate containing only ethylene oxide and propylene oxide chains, RENEX 20 (trade mark, I.C.I. United States, Inc.~ a nonionic, polyoxyethylene ester of mixed fatty acids and resin acids.
In accordance with a preferred embodiment of the present invention, the surfactant preferably com-prises a combination of a hydrocarbon-derivative sur-factant and an abietic acid-derivative surfactant which are present in substantially equal quantities.
The hydrocarbon-derivative surfactant prefer-ably employed in the cleaner may be represented by the following general formula:
R(OR~ )nOH

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Wherein R is an alkyl or alkylaryl group of 8-22 carbon atoms; R' i.s a divalent radical selected from ethyl, propyl and combinations thereof and n i5 an integer from 7 to 22. The desired concentration of this surfactant is bound at the lower end by the extent of cleaning required and at the upper end by the stabi-lity of the surfactant in the aqueous acidic cleaner.
The range of about 0.1 to about 30 g/l or higher has been found suitable with a range of about 0.5 to about

2.1 g/l being preferred and concentration of about 1.3 g/l being most preferred. Commercially available sur-factants believed to fall within the above general formula include T~ITON CF-10 (trade mark, Rohm & Haas Company), A~TAROX LF-330, ~NTAROX BL-330 and IGEPAL CA-630 (trade marks, GAF Corporation), TRYCOL LF-l (-trade mark, Emery Industries, Inc.) and PLURAFAC D-25 (trade mark, BASF Wyandotte Corporation). These surfactants contain both alkyl and alkylaryl R groups, ethoxy and propoxy R' groups with n values ranging from to 16.
The abietic acid-derivative surfactant may be represented by the general formula:
A(R')n~
wherein R' and n are as defined above and A is the abietie acid radical. The abietic acid-derivative sur-faetant functions conjointly with the hydrocarbon-derivative surfactant to remove all of the types of organie contaminants whieh may remain on the surface ,,,,,; 10 ~372~3 subsequent to ordinary cold forming operations. The desired concentration ranges are the same as those for the hydrocarbon-derivative surfactants. Commercially available surfactants are SURFACTANT AR 150 (trade mark) supplied by Hercules, Inc. and PEGOSPERSE 700-T0 (trade mark) supplied by Glyco Chemicals, Inc. Both of these commercially available surfactants serve as source of an abietic acid ester containing approximately 14 to 16 mols of ethoxylation.
It has been found that variations in the alkylene oxide end groups of either of the above sur-ac-tants does not adversely affect their efficacy. The final hydroxy group may be replaced, for example, by a chloride substituent. Alkyl or aryl substitutions may also be made.
The cleaner composition in addition to the surfactant further contains as essential constituents, a combination of phosphate ions and sulfate ions present in an amount of about 2 to about 100 g/l with amounts of about 5 to about 35 g/l being preferred. The phosphate ions preferably comprise from about 30 percent to about 80 percent by weight of the combined weight of phosphate and sulfate ions present.
The phosphate ions can be introduced in the form of any one of a variety of bath compatible alkali metal and ammonium phosphate salts although phosphoric acid itself constitutes the preferred material.

~J 11 As in the case of the phosphate ionS, the sulfate ions can be introduced in the foxm of any one of a variety of bath compatible salts including alkali metal and ammonium salts although sulfuric acid itself comprises the preferred material. In either event, the phosphate and sulfate ions are introduced to preferably ; provide a hydrogen ion concentration to provide an acidity of the operating cleaner composition of a pH
not in excess of 2 with a pH of about 0.5 to about 1.2 being preferred and a pH of about 0.8 being particularly satisfactory. The appropriate concentration of hydrogen ions to provide the desired acidity can conveniently be achieved by appropria-te additions of phosphoric acid and sulfuric acid which simultaneously introduces the requisite quantity of phosphate and sulfate ions in the solution.
When a bright shiny aluminum appearance is required, the concentration of the combined phosphate and sulfate ions is preferably maintained at a level below about 17 g/l. When a frosty, etched aluminum surface appearance can be tolerated as in the case of over-all painted or decorated containers, the combined concentra-tion of phosphate and sulfate lons can be increased up to about 100 g/l. Since the efficacy of cleaning and etching of the aluminum surface is related to the time, temperature, and acidity of the cleaning treatment, the .r 7~:~8 '' :. concentration of toe actiVe constituents can be adjusted for any specific situation within the parameters herein-above defined to attain the desired cleaning and appear-ance of the aluminum surfaces.
In accordance with the process aspects of the present invention, the aqueous acidic cleaning com-position is applied to the aluminum surface to be cleaned by immersion, flooding and preferably by spray application in view of the configuration of the con-tainers. The cleaner solution is applied at moderate temperatures ranging from about 100 up to about 160F
with temperatures of about 110 to about 140F being preferred for energy conservation considerations. the contact time of the cleaner with the aluminum surface will vary depending upon the magnitude and nature of ; the contaminants present thçreon and Jill usually range from as low as about 10 seconds up to about 5 minutes with contact times of less than about 2 minutes such as about 30 seconds to about 1 minute being sufficient for most conditions.
The cleaning composition may also optionally contain any one of a variety of commercially available anti-foaming agents in usual amounts in the event ob-~ectionable foaming of the cleaning solution occurs depending upon the particular mode of application.

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A so-called "TR-4" test procedure has been developped to evaluate the resistance to discoloration of a cleaned and treated but unlacquered aluminum sur-face, also called "Bare Corrosion Test" which simulates exposure of the unpainted exterior bottom of an aluminum can during a commercial Pasteurization process. For this purpose, an aqueous solution is prepared simulat-ing a typical water composition employed in the Pas-teurization process containing 82.4 parts per million (ppm) sodium chloride, 220 ppm sodium bicarbonate, 2180 ppm of a water conditioner and the balance de-ionized water to form one liter. The water conditioning agent employed is a proprietary product supplied by DuBois Chemicals, Inc. under the trade mark DUBOIS 915 which exhibits a total alkalinity of 5.8 percent Na20 and on analysis contains sodium nitrate, carbonate, triethanolamine and a dodecylphenyl polyethylene glycol.
The test procedure employing the aforementioned TR-4 test solution involves subjecting the treated and un-lacquered containers to the solution for a specified time, e.g. 30 minutes while maintained at a specified elevated temperature such as 150F plus or minus 5F.
Following the test, the test specimen is removed, rinsed with water, dried and visually inspected for discoloration. Test specimens are rated from 1 no staining or discoloration) to 10 (dark gold to grey-black discoloration or extensive non-uniform mottling ~C~7%~8 of the surface). Ratings of l through 4 are generally considered commercially acceptable in the aluminum can industry whereas ratings of 5 through 10 are not accep-table.
In order to further illustrate the improved -I fluoride-free cleaner composition and method of the present invention, the following specific examples are I, provided It will be understood that the examples are provided for illustrative purposes and no-t intended to be limiting of the scope of the present invention as herein described and as set forth in the subjoined claims.

For comparison purposes, a fluoride-free aqueous acidic cleaning solution is prepared containing 7.7 g/l sulfuric acid (100~), about 2 g/l of an abietic acid-derivative surfactant commercially designated as AR-150, about 2 g/l of a hydrocarbon-derivative surfac-tant commercially available under the designation Trycol LF-l, and the balance water. A total of 19 liters of the cleaning solution is provided at a nominal pH
of about 1.2.
Aluminum cans from the can trimming operation having residual organic lubricants and coolants on the - 25 surface thereof are cleaned with the cleaner for a period of 1 minute by spray application at a tempera-ture of about 140F. The cleaned cans thereafter are ,, '"I

-~C~72~3 subjected to a warm tap water rinse at about 120F or a period of 15 seconds.
The cleaned and rinsed cans are thereafter subjected to a surface treatment employing an aqueous chromium-free treating solution sold under the designa-tion BONDERITE K-780 (trade mark) available from Parker Division of looker Chemicals & Plastics Corpora-tion. The treating solution is applied at a pH of 3.7 by spray application for a period of 15 seconds at a temperature of about 120 F.
The treated cans following the treatment are again spray water rinsed for a period of 15 seconds with tap water at 120F followed by a 15 second cle-toted water spray rinse whereafter the can is dried in a recirculating hot air oven for a period of 5 minutes at 380F
The bottom portion of the can is removed as a test sample ancl is subject to the TR-4 test in accor-dance with the procedure previously described. An in-spection of the unlacquered exterior bottom surface ofthe test specimen at the conclusion of the TR-~ test reveals a rating of about 10 which is generally commercially unacceptable. At the completion of the cleaning treatment and prior to the conversion coating treatment, the can was observed to the water break-free with no etching of the surfaces thereof.

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A cleaning solution is prepared identical to that described in Example 1 with the exception that the solution contained an additional 4.5 g/l of phosphoric acid (100%) and a trimmed aluminum can was processed in accordance with the same sequence as described in Exam-ple 1. At the completion of the clean:ing treatment, the ;l surface of the can was observed to be water break-free I, with a little etching of the surface thereof. Exposure of the bottom of the can to the TR-4 test evidenced a rating of 4.

A cleaning solution is prepared similar to that of Example 1 with the exception that 9 g/l of phosphoric acid (100%) is added and trimmed aluminum cans are processed in accordance with the same sequence as in Examples l and 2. At the completion of the cleaning treatment the surface of the can was water break-free with a desirable degree of etching. The can bottom after subjection to the TR-~ test had a rating of 0 which is commercially acceptable.

An aqueous cleaning solution was prepared similar to thak described in Example 3 except that the 1~3~2~8 . .

phosphoric acid concentration was increased to 13.5 g/l and the temperature of the cleaning solution was reduced from 140F to 130~. The results obtained at the lower temperature and at the higher phosphate ion concentra-tion were similar to those obtained on the test specimen processed in accordance with Example 3.
The results of Examples 2-4 clearly evidence the unexpected synergistic effect of sulfate and phos-phate ions in combination with a surfactant to effect satisfactory cleaning and etching of an aluminum can surface to remove organic soils and metallic smut while at the same time retaining the attractive shiny metallic appearance of the can and without excessive etching.
Tests conducted employing a solution similar to that of Example 1 to which 19 g/l of hydrochloric acid (100%) were added produced excessive etching of the surface resulting in a blacked-streaked and frosty undesirable exterior appearance and the TR~4 tes-t results were .~ commercially unsatisfactory. Similarly, the addition of 10.4 g/l of nitric acid to the cleaner formulation of Example 1 resulted in substantially no etching of the surface and TR-4 test results which were commercially unsatisfactvry.
The make-up and replenishment of operating aqueous cleaning solutions in accordance with the present invention can conveniently be achieved employ-ing a concentrate containing each of the essential .

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constituents in appropriate proportions such that upon dilution with water, an operatiny bath of the appropri-ate concentration is attained and is maintained. The maximum concentration of the various constituents in the concentrate will to some extent depend upon the stability and compatibility of the ingredients at such higher concentrations. Conventionally, aqueous concen-trates containing up to about 200 g/l surfactant, up to about 500 g/l of a controlled combination of phosphate ions and sulfate ions are suitable for dilution with an appropriate amount of water to produce an operating cleaning solution of the desired concentration.
While it will be apparent that the preferred embodiments of the invention disclosed are well calcu-lated to fulfill the objects above sta-ted, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.
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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

1. An aqueous acidic fluoride-free composition suitable for cleaning aluminum surfaces consisting essentially of at least one surfactant present in an amount of about 0.1 to about 30 g/l, a controlled combination of phosphate ions and sulfate ions present in an amount of about 2 to about 100 g/l of which about 30 percent to about 80 percent by weight comprise phosphate ions, and hydrogen ions present in an amount to provide an acidic pH not in excess of about 2.

2. The composition as defined in claim 1, in which said hydrogen ions are present in an amount to provide a pH of about 0.5 to about 1.2.

3. The composition as defined in claim 1, in which said hydrogen ions are present in an amount to provide a pH of about 0.8.

4. The composition as defined in claim 1, in which said surfactant is present in an amount of about 0.5 to about 10 g/l.

5. The composition as defined in claim 1, in which said surfactant comprises a mixture of a hydro-carbon-derivative surfactant and an abietic acid-derivative surfactant.

6. The composition as defined in claim 1, in which said combination of said phosphate ions and said sulfate ions are present in an amount of about 5 to about 35 g/l.

7. The composition as defined in claim 1, in which said hydrogen ions are introduced as phosphoric acid, sulfuric acid and mixture thereof.

8. An aqueous acidic fluoride-free concentrate suitable for dilution with water to form a cleaning composition for aluminum surfaces consisting essentially of at least one surfactant present in an amount of about 0.1 to about 30 g/l, a controlled combination of phosphate ions and sulfate ions present in an amount of about 2 to about 100 g/l of which about 30 percent to about 80 percent by weight comprise phosphate ions, said concentrate consisting essentially of up to about 200 g/l surfactant and up to about 500 g/l of a control-led combination of phosphate ions and sulfate ions in which the phosphate ions comprise about 30 percent to about 80 percent by weight and hydrogen ions present in an amount sufficient to provide a pH less than 0.

9. A process for cleaning aluminum surfaces comprising the steps of contacting an aluminum surface to be cleaned with an aqueous acidic fluoride-free composition as defined in claims 1, 2 or 5 for a period of time sufficient to effect a desired cleaning and etching of the aluminum surface and thereafter discon-tinuing contact of the aluminum surface with said aqueous acidic composition.

10. A process for cleaning aluminum surfaces comprising the steps of (a) contacting an aluminum surface to be cleaned with an aqueous acidic fluoride-free solution consisting essentially of at least one surfactant present in an amount of about 0.1 to about 30 g/l, a controlled combination of phosphate ions and sulfate ions present in an amount of about 5 to about 35 g/l of which about 30 percent to about 80 percent by weight comprise phosphate ions and hydrogen ions present in an amount to provide an acidic pH not in excess of about 2 at a temperature of about 100° to about 160°F for a period of time of about 10 seconds to about 1 minute, and (b) rinsing the aluminum surface to remove the aqueous acidic solution therefrom.

11. A process in accordance with claim 10, wherein the sulfate ions in step (a) are present in an amount of about 6 to about 15 g/l.

12. A process in accordance with claim 10, wherein the phosphate ions in step (a) are present in an amount of about 10 to about 20 g/l.

13. A process in accordance with claim 10, wherein the treatment time in step (a) is from about 30 seconds to about 1 minute.

14. A process in accordance with claim 10, wherein the aluminum surface is contacted with the aqueous solution by spraying said solution onto the surface.

15. A process in accordance with claim 10, wherein the solution temperature is maintained in the range of from about 115°F to about 140°F.

16. A process in accordance with claim 10, wherein the aluminum surface is the surface of an aluminum can.