U.S. patent number RE32,661 [Application Number 06/634,668] was granted by the patent office on 1988-05-03 for cleaning aluminum at low temperatures.
This patent grant is currently assigned to Amchem Products, Inc.. Invention is credited to Robert E. Binns.
United States Patent |
RE32,661 |
Binns |
May 3, 1988 |
Cleaning aluminum at low temperatures
Abstract
Acid cleaning of aluminum surfaces is accomplished employing a
composition comprising hydrofluoric acid and sulfuric acid. More
specifically, this invention relates to a composition and method
for treating aluminum containers at low temperatures.
Inventors: |
Binns; Robert E. (Roslyn,
PA) |
Assignee: |
Amchem Products, Inc. (Ambler,
PA)
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Family
ID: |
27033267 |
Appl.
No.: |
06/634,668 |
Filed: |
July 27, 1984 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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189741 |
Sep 23, 1980 |
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442726 |
Feb 14, 1974 |
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Reissue of: |
607154 |
Aug 25, 1975 |
04009115 |
Feb 22, 1977 |
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Current U.S.
Class: |
510/257; 134/3;
134/40; 134/41; 148/270; 252/79.3; 252/79.4; 510/108; 510/421;
510/426 |
Current CPC
Class: |
C23G
1/125 (20130101) |
Current International
Class: |
C23G
1/02 (20060101); C23G 1/12 (20060101); C11D
001/72 (); C11D 007/08 (); C23C 022/06 (); C23G
001/12 () |
Field of
Search: |
;148/6.14R,6.27 ;156/665
;134/3,40,41 ;252/79.3,79.4,142,146,147 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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536710 |
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Feb 1957 |
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CA |
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850046 |
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Aug 1970 |
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CA |
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868314 |
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Apr 1971 |
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CA |
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1202615 |
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Oct 1965 |
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DE |
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881701 |
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May 1943 |
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FR |
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543770 |
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Mar 1942 |
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GB |
|
877240 |
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Sep 1961 |
|
GB |
|
115630 |
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Sep 1975 |
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GB |
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Other References
Graham, Kenneth A., Editor, Electroplating Engineering Handbook,
3rd Ed., Van Nostrand Reinhold Co., N.Y., 1971, p. 169. .
Murphy, James A., Editor, Surface Preparation and Finishes for
Metals, McGraw Hill Book Co., 1971, pp. 24, 25 & 29. .
Spring, S., Ph.D.: Industrial Cleaning, Prisem Press, Melbourne,
(1974), pp. 33 & 34. .
Hess et al, "The Surface Treatment at Room Temperature of Al Alloys
for Spot Welding", J. American Welding Soc., Sep. 1944, pp.
417s-423s. .
Akers et al, "Cleaning Aluminum", Soap and Sanit. Chem., vol. 17,
Apr. 1941, pp. 25-27, 71, 73-74. .
Wernick et al, Surface Treatment and Finishing of Aluminum and its
Alloys, 1956, pp. 74, 89, 129, 147. .
Harris et al, Annotated Bibliography of Aluminum Cleaning, Jan.
1943, (pp. 33-36); Mar. 1943, (pp. 33-38); May 1944, (pp. 35-40).
.
Harris, Metal Cleaning Bibliographical Abstracts, Publ. No. 90,
(1949-pp. 1-68); Publ. No. 90A, (1950, pp. 1-27); Publ. No. 90D,
(1957, pp. 1-38). .
Mona Industries Inc., "Monaterge LF-945", Tech. Bulletin No. 230,
Dec. 1975, pp. 1-2..
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Primary Examiner: Albrecht; Dennis
Attorney, Agent or Firm: Barron; Alexis
Parent Case Text
BACKGROUND OF INVENTION
.Iadd.This is a continuation of reissue application Ser. No.
189,741, filed Sept. 23, 1980, now abandoned. .Iaddend.
This is a Continuation-In-Part Application of Application Ser. No.
442,726 filed on Feb. 14, 1974 and now abandoned.
Claims
I claim: .[.1. An aqueous cleaning composition for removing and
dissolving aluminum fines and cleaning lubricating oils from
aluminum surfaces comprising of from about 1 to about 10
grams/liter of sulfuric acid and from about 0.005 to about 0.1
grams/liter of hydrofluoric acid..]. .[.2. The composition of claim
1, wherein the pH is from about 1.0 to about 1.8..]. .[.3. The
composition of claim 1, further comprising a surfactant in an
amount from about 0.1 to about 10 grams/liter..]. .[.4. The
composition of claim 3, wherein the surfactant is selected from the
group consisting of nonionic and anionic surfactants..]. .[.5. The
composition of claim 4, wherein the surfactant is selected from the
group consisting of sodium 2-ethyl hexyl sulfate and an alkyl
polyethoxylated ether..]. .[.6. An aqueous cleaning composition for
removing and dissolving aluminum fines and cleaning lubricating
oils from aluminum surfaces consisting essentially of about 3 to
about 5 grams/liter of sulfuric acid, from about 0.01 to about 0.03
grams/liter of hydrofluoric acid, and from about 0.1 to about 10
grams/liter of an alkyl polyethoxylated ether nonionic
surfactant..]. .Iadd.7. An acidic aqueous cleaning solution having
a pH of less than 2.0 and consisting essentially of about 1 to
about 10 g/l of sulfuric acid, about 0.005 to about 0.1 g/l of
hydrofluoric acid, and about 0.1 to about 10 g/l of a surfactant
selected from the group consisting of nonionic and anionic
surfactants, wherein the sources of said acids are respectively
sulfuric acid and hydrofluoric acid, wherein said solution is free
of a corrosion inhibitor in a corrosion-inhibiting amount and of a
sludge-forming material, and wherein said solution is effective in
removing and dissolving aluminum fines and in cleaning lubricating
oils from the surfaces of drawn and ironed aluminum cans of 3004
alloy at a temperature within the range of about 110.degree. F. to
about 135.degree. F., said cleaned surfaces being
water-break-free.
.Iaddend. .Iadd.8. A cleaning solution according to claim 7 wherein
the concentration of said sulfuric acid is about 3 to about 5 g/l.
.Iaddend. .Iadd.9. A cleaning solution according to claim 7 wherein
the concentration of said hydrofluoric acid is about 0.01 to about
0.03 g/l. .Iaddend. .Iadd.10. A cleaning solution according to
claim 7 wherein the concentrations of said sulfuric and said
hydrofluoric acid are respectively about 3 to about 5 g/l and about
0.01 to about 0.03 g/l. .Iaddend. .Iadd.11. A cleaning solution
according to claim 7, 8, 9 or 10 wherein said pH is about 1.0 to
about 1.8. .Iaddend. .Iadd.12. A cleaning solution according to
claim 7, 8, 9 or 10 wherein said pH is about 1.2 to about 1.5.
.Iaddend. .Iadd.13. A cleaning solution according to claim 7, 8, 9
or 10 wherein said surfactant is a nonionic surfactant. .Iaddend.
.Iadd.14. A cleaning solution according to claim 13 wherein said pH
is about 1.0 to about 1.8. .Iaddend. .Iadd.15. A cleaning solution
according to claim 13 wherein said pH is about 1.2 to about 1.5.
.Iaddend.
Description
Containers comprised of aluminum and alloys thereof are produced in
a drawing and forming operation, referred to as drawing and
ironing, which results in the deposition of lubricants and forming
oils on the surface. In addition, residual aluminum fines, i.e.
small particles of aluminum, are deposited on the interior and
exterior surfaces of the container during the forming operation.
Ordinarily, the exterior surface of the container will have smaller
quantities of aluminum fines since during the drawing and ironing
step the exterior surface is not subject to as much abrasion from
the die as the interior surface.
Prior to any processing steps, such as conversion coating and
sanitary lacquer deposition, the surfaces of the aluminum
containers must be clean and water-break-free so that there are no
contaminants which prevent further processing and which render the
containers unacceptable for use.
Acid cleaners have been employed to clean the aluminum surfaces and
to remove aluminum fines deposited on the interior walls of
aluminum containers. Acid cleaning is ordinarily accomplished at
temperatures from 185.degree. F. to 200.degree. F. in order to
remove or dissolve the aluminum fines and to remove the lubricants
and forming oils so that the surface is rendered water-break-free.
The cleanliness of the aluminum surface is measured by the ability
of the interior and exterior surfaces of the formed aluminum
container to support a continuous break-free film of water, that is
to be water-break-free.
Due to the high temperatures at which cleaning is accomplished,
that is from 185.degree. F. to 200.degree. F., and the acidity of
the cleaning composition, the processing equipment employed to heat
the cleaning composition, particularly the fire tubes of gas fired
heat exchangers, are susceptible to corrosion. Furthermore, the
high temperatures increase operating costs and fuel
consumption.
Chromic acid or salts thereof have been utilized to minimize the
corrosion of the processing equipment by inhibiting the corrosive
attack of the acid cleaning composition on the processing
equipment. An important shortcoming which cleaners of this kind
possess is the inherent toxicity of the hexavalent and trivalent
chromium compounds contained therein and the resultant waste
disposal problem created by the presence of chromium in the cleaner
effluent.
Attempts have been made to include other additives in the cleaning
compositions to provide efficient cleaning. Such additives have
included fluoride. Maintenance and control of acidic cleaners at
low pH's has proven impractical, especially when fluorides are
present. Furthermore, as such cleaning is effected at high
temperatures, the fluoride when present in high concentrations can
attack the metal surface and etch the surface which is undesirable,
especially when cleaning of containers is to be effected.
The principal object of this invention is to provide a cleaning
composition for aluminum for removing and dissolving aluminum fines
and for cleaning lubricating oils from the aluminum surface.
An object of this invention is to provide a process for cleaning
aluminum surfaces at low temperatures thereby reducing corrosion
and attack of processing equipment and reducing heating costs and
heating fuel consumption.
An added object of this invention is to provide a cleaning
composition possessing good cleaning ability and preventing
corrosive attack of processing equipment while having no chromate
therein.
Another object is to provide a cleaning solution which produces no
sludge during operation.
A concomitant object of this invention is to provide a cleaning
solution having relatively low concentrations of hydrofluoric acid,
which can be easily controlled and which enables the cleaning of
aluminum surfaces with little or no etching of the surface.
DETAILED DESCRIPTION OF THE INVENTION
I have discovered a composition and process for the cleaning of
aluminum surfaces, said composition comprising from about 0.005 to
about 0.1 grams/liter of hydrofluoric acid and from about 1 to
about 10 grams/liter of sulfuric acid. When an aqueous cleaning
composition comprising hydrofluoric acid and sulfuric acid is
employed at the concentrations specified above, the aluminum
surface is cleaned of lubricant and metallic fines at temperatures
as low as from about 90.degree. F. to about 135.degree. F.
It should be understood that the term aluminum surface used herein
includes aluminum and aluminum alloys in which aluminum is the
principal constituent. It should be understood that by "cleaning
composition," or "cleaning solution" I mean the aqueous acidic
cleaning bath of the present invention comprising hydrofluoric acid
and sulfuric acid.
The surprising results obtained with the use of the cleaning
solution include the removal and dissolution of aluminum fines from
a formed aluminum container, both on the interior walls and dome of
said container, at temperatures within the range of from about
90.degree. F. to about 135.degree. F. In addition, it has been
found that with the use of the cleaning solution of the present
invention corrosive attack of the processing equipment,
particularly the fire tubes of gas fired heat exchangers, is
reduced considerably. This is accomplished without the use of any
inhibitors in the cleaning solution, such as hexavalent
chromium.
I have found that active fluoride is a necessary constituent which
is responsible for assisting in dissolution of the aluminum fines
and oil film removal. In the present cleaning process it is
essential that the active fluoride be maintained within specified
limits, since the active fluoride affects the aluminum fine
dissolution and oil film removal.
The term "active fluoride" means the fluoride present in the
operating cleaning solution and measurable at a given pH by a
fluoride sensitive electrode of the potentiometric type. For
example, electrodes of this type and their use are described in
U.S. Pat. No. 3,431,182 which is hereby incorporated by reference.
The electrodes described therein are known to the art as fluoride
specific ion electrodes.
Due to the low concentration of hydrofluoric acid in the cleaning
solution of this invention, a potentiometric type electrode is
found to be preferable for measuring active fluoride. Other
measuring devices that are not of the potentiometric type are
insensitive to the concentration of hydrofluoric acid in the
cleaning solutions of the present invention, as they are useful
only in concentrated solutions or solutions having higher
concentrations of hydrofluoric acid.
With the use of the potentiometric type electrode, the active
fluoride measurement is measured as a potential which is
proportional to or related to the actual fluoride ion concentration
in the solution.
It is known that in acid solutions containing fluoride, hydrogen
ion complexes a portion of the fluoride forming undissociated HF
and HF.sub.2.sup.-. In addition, when aluminum is dissolved in such
solutions, Al.sup.+3 also complexes fluoride. Due to the presence
of these complexing agents, it is difficult to measure actual free
fluoride ion concentration without extensive sample manipulation.
However, by the use of the potentiometric type electrode, once a
reference point has been arrived at by measuring a make-up cleaning
solution potential and taking this potential as the zero point, it
is inconsequential how much fluoride is actually complexed. The
potential increases negatively in more concentrated solutions, that
is when the active fluoride concentration increases, and the
potential increases positively in more dilute solutions, that is
when the active fluoride concentration decreases. When aluminum
ions enter the solution as aluminum fines are removed from the
surface, the electrode potential becomes more positive as the
amount of active fluoride decreases. When additions of hydrofluoric
acid are effected, the potential becomes less positive and
approaches the zero point again. Since the potentiometric type
electrode will measure the active fluoride in the solution, taking
no account of any complexed fluoride, additions of active fluoride,
preferably as hydrofluoric acid, can be made to the operating
cleaning solution to return the potential measurement to the
original zero reference point.
It has been discovered that as a cleaning solution is used,
aluminum is dissolved off the surface being treated at a specific
rate. In general, cleaning solutions of the present invention will
have operating characteristics such that at make-up the aluminum
dissolution rate is from about 8 to about 25 milligrams per square
foot (0.009 to 0.027 mg/cm.sup.2) of aluminum surface treated. It
has been observed that best results, with minimal etch of the
surface, are obtained when the aluminum dissolution rate is from 9
to 20 milligrams per square foot (0.01 to 0.022 mg/cm.sup.2) of
aluminum surface treated. This dissolution rate occurs at make-up
of a cleaning solution having from about 0.005 to about 0.1
grams/liter of hydrofluoric acid. By establishing a zero potential
point with a potentiometric type electrode at make-up of the
cleaning solution, and by recording the potential measurements as
metal surfaces are processed and cleaned, the aluminum dissolution
rate is maintained within the preferred range by additions of
active fluoride, preferably as hydrofluoric acid. So, the
potentiometer electrode is used as a guideline for determining when
to adjust the amounts of active fluoride in solution, and also to
maintain sufficient active fluoride therein to effect a desirable
aluminum dissolution rate.
The active fluoride suitable for use herein is preferably added to
the cleaning composition as hydrofluoric acid. A simple fluoride
salt can also be utilized, for example, an alkali metal fluoride or
bifluoride such as sodium fluoride, ammonium fluoride or
bifluoride. Complex fluoride can be employed. However, greater
concentrations of complex fluoride will be necessary to yield
desirable amounts of active fluoride, as the hydrolysis of complex
fluorides is not as substantial as with the simple fluoride, to
liberate the required active fluoride.
The amount of active fluoride in the cleaning solution is expressed
herein as a concentration of hydrofluoric acid. This means that the
active fluoride is in the form of dissociated fluoride whose
concentration is expressed as the concentration of hydrofluoric
acid.
The active fluoride in the cleaning solution aids in the removal of
aluminum fines on the metal substrate which have formed during the
forming operation. A surprising aspect of this invention is that
the cleaning process can be effected when the amount of
hydrofluoric acid present in the solution, is as low as 0.005
grams/liter. I have found that by employing the preferred amount of
hydrofluoric acid, resulting in the presence of sufficient active
fluoride, removal of the aluminum fines is accomplished without
vigorous attack of the underlying aluminum surface. Of course,
should the active fluoride be depleted in the cleaning solution,
preferably it can be replenished by addition of hydrofluoric
acid.
Sulfuric acid in the cleaning solution should be present in an
amount of from about 1 to about 10 grams/liter. It is preferred
that the sulfuric acid be present in an amount from about 3 to
about 5 grams/liter.
The hydrofluoric acid should be present in the cleaning solution in
an amount from about 0.005 to about 0.1 grams/liter. For optimum
results, it is preferred that the hydrofluoric acid be present in
an amount from about 0.01 to about 0.03 grams/liter.
In the preferred embodiment of this invention an operating cleaning
solution is employed comprising hydrofluoric acid and sulfuric acid
wherein the concentration of constituents, at the beginning of
operation as well as upon replenishment, is maintained such that
the sulfuric acid is present in amount from about 3 to about 5
grams/liter, and the active fluoride is maintained at the level
measured at make-up, that is when the hydrofluoric acid
concentration at make-up is about 0.01 to about 0.03 grams/liter.
When a cleaning solution is operated and maintained within these
preferred limits it has been found that excellent cleaning of the
aluminum surface will result. A most surprising result is that the
surface will be free of oils and aluminum fines without the
corrosive attack of processing equipment occurring.
The cleaning solution preferably is prepared by employing aqueous
concentrates consisting of sulfuric acid and water, and
hydrofluoric acid and water. The aqueous concentrates can be added
to an appropriate amount of water to prepare a working cleaning
solution having constituent concentrations within the operative
ranges set forth herein. Alternatively, the hydrofluoric acid and
sulfuric acid can be prepared as a concentrate and can be added
simultaneously as one component to water to form the aqueous
cleaning composition at concentrations for use.
Surfactants are desirably included in the cleaning composition.
Such materials enhance the cleaning performance considerably. It
has been observed that the use of surfactants in the cleaning
solution assist in more rapid wetting of the surface and the
removal of lubricant and oils. The surface active agents to be
employed herein can be anionic, cationic, or nonionic. Preferably
nonionic or anionic surface active agents are used. Examples of
surface active agents that can be utilized are Tergitol 08 (sodium
2-ethyl hexyl sulfate), Triton DF-16 (a modified polyethoxylated
straight chain alcohol), Polytergent S-505 LF (a modified
polyethoxylated straight chain alcohol), Surfonic LF-17 (an alkyl
polyethoxylated ether), Plurafac RA-30 (a modified oxyethylated
straight chain alcohol), Triton X-102 (an octylphenoxy polyethoxy
ethanol), Plurafac D-25 (modified oxyethylated straight chain
alcohol) and Antarox BL 330 (a modified polyethoxylated straight
chain alcohol). The surface active agent present in the cleaning
composition can be a combination of one or more particular surface
active agents. The surface active agent can be present in the
cleaning composition in an amount from about 0.1 to about 10
grams/liter.
Cleaning compositions having the following formulas can be
employed:
______________________________________ Grams
______________________________________ FORMULA I Hydrofluoric Acid
0.02 Sulfuric Acid 4.0 Anionic Surfactant (Tergitol 08) 1.0 Water
to make 1 liter FORMULA II Hydrofluoric Acid .005 Sulfuric Acid 6.0
Nonionic surfactant (Trition DF 16) 1.0 Water to make 1 liter
FORMULA III Hydrofluoric Acid .01 Sulfuric Acid 4.0 Nonionic
Surfactant (Plurofac RA 30) 2.0 Water to make 1 liter
______________________________________
The metal surface should be cleaned employing techniques that
result in a completely water-break-free surface. The cleaning
solution can be applied to the aluminum surface utilizing any of
the contacting techniques known to the art. Preferably, application
will be effected by conventional spray or immersion methods. The
time of treatment of the surface with the cleaning solution need
only be long enough to insure complete wetting of the surface and
can be as long as 10 minutes. Preferably, the surface should be
treated for a time from about 15 seconds to about 2 minutes.
The aluminum fines and forming oils are removed from the aluminum
surface by the cleaning solution at temperatures lower than
ordinarily expected. The cleaning process can be operated at
temperatures from about 90.degree. F. to about 135.degree. F. It is
preferred that the cleaning process be operated at temperatures
from about 110.degree. F. to about 125.degree. F. Optimum results
are obtained when the cleaning process is operated at temperatures
from about 120.degree. F. to about 125.degree. F. This is a
distinct advantage of the present invention over prior art
processes, as the low operating temperatures with good cleaning
results prevents accelerated corrosion and attack of processing
equipment.
In accordance with the invention the cleaning solution is highly
acidic, having a pH below 2.0. The amount of sulfuric acid and
hydrofluoric acid can be varied within limits in accordance with
the ranges set forth hereinabove so that the pH of the cleaning
solution can be adjusted. Preferably the pH of the cleaning
solution is adjusted to from about 1.0 to about 1.8, and optimum
results, that is excellent cleaning with minimal etching, are
obtained when the pH of the cleaning solution is adjusted to from
about 1.2 to about 1.5.
In accordance with broader aspects of the invention, there is
considerable flexibility available with respect to portions of the
overall processing of the aluminum substrate. In particular,
chemical processing steps can be effected prior to cleaning such
as, for example, a hot water prerinse of the surface. Following
application of the cleaning solution, the surface can be rinsed
with water and then dried. Ordinarily a water rinse is necessary to
remove any remaining residues which may have remained after the
cleaning step. After the rinse step, the aluminum surface may be
contacted with conversion coating solutions or siccative finish
coating compositions well known to the art. Generally, the coating
solution will be applied directly after the cleaning operation or a
short period of time thereafter. However, as specified hereinabove,
the cleaned surface can be dried and the coating steps may be
accomplished at a later time.
The following examples are illustrative of this invention and are
not considered as limiting for other materials and operating
conditions falling within the scope of this invention which might
be substituted.
EXAMPLE I
Aluminum container test specimens of 3004 alloy, drawn into single
piece containers, were employed in this procedure. The containers
had been subjected to a drawing operation and were covered with
aluminum fines and drawing oils.
The test specimens were treated as follows:
1. Treated for 60 seconds by spraying the interior and exterior of
the specimens with the solutions listed in Table 1.
2. Rinsed with water by immersion in cold water for 30 seconds at
ambient temperature.
Control specimens were treated with aqueous compositions comprising
acids, as indicated in Table 1, such as sulfuric, hydrochloric,
phosphoric, and nitric acid, as well as specified combinations or
mixtures of these acids. The concentrations of the aqueous
solutions and the constituents therein are listed in Table 1. The
temperature of each of the respective solutions when employed to
treat the test and control specimens is listed in Table 1.
Except when an anionic surfactant (Tergitol 08) was employed in the
solutions as indicated in Table 1, all other compositions contained
0.1 grams/liter of a nonionic surfactant (0.1 gram/liter of Triton
X-102).
The aluminum surfaces were tested for water-break following
cleaning. The container surfaces were treated by measuring the
percent of water-break on the surface, that is the percent of the
total surface area which did not support a continuous film of
water. The results are listed in Table 1.
The results reported in Table 1 include a determination of the
presence of aluminum fines remaining on the surface after
processing was completed. The brightness and appearance of the test
specimens at the end of the processing procedure was also observed.
The brightness quality was determined by visually rating the degree
of brightness of the surface from 1 to 5 wherein the brightness
rating of 1 represents best performance and appearance and rating
of 5 represents poor appearance. The presence of aluminum fines on
the interior surface was determined by rubbing the surface with a
clean white cloth and observing the fines deposited on the cloth.
The presence of fines is evidenced by a dark black residue on the
white cloth. The amount of fines present is expressed in Table 1 in
gradations from excellent (E) for no residue, good (G) for very
light residue, fair (F) for moderate residue, to poor (P) for very
heavy residue.
TABLE 1
__________________________________________________________________________
Percent Waterbreak Interior Interior Temperature Exterior Interior
Wipe Appearance
__________________________________________________________________________
Aqueous Composition 2 g/l H.sub.2 SO.sub.4 150.degree. F. 80 80 G 4
4 g/l H.sub.2 SO.sub.4 150.degree. F. 60 30 F 4 6 g/l H.sub.2
SO.sub.4 150.degree. F. 50 10 P 4 2 g/l HCl 150.degree. F. 100 90 G
4 4 g/l HCl 150.degree. F. 100 80 G 4 6 g/l HCl 150.degree. F. 100
80 G 4 2 g/l H.sub.3 PO.sub.4 150.degree. F. 90 80 G 4 4 g/l
H.sub.3 PO.sub.4 150.degree. F. 50 80 E 4 6 g/l H.sub.3 PO.sub.4
150.degree. F. 70 50 E 3 2 g/l HNO.sub.3 150.degree. F. 100 100 E 5
4 g/l HNO.sub.3 150.degree. F. 100 90 E 5 6 g/l HNO.sub.3
150.degree. F. 100 90 G 5 2 g/l H.sub.2 SO.sub.4 + 2 g/l HCl
150.degree. F. 90 30 P 3 3 g/l H.sub.2 SO.sub.4 + 3 g/l HCl
150.degree. F. 80 30 P 3 Bath Composition 2 g/l H.sub.2 SO.sub.4 +
2 g/l H.sub.3 PO.sub.4 150.degree. F. 70 5 F 2 3 g/l H.sub.2
SO.sub.4 + 3 g/l H.sub.3 PO.sub.4 150.degree. F. 70 5 G 2 2 g/l
H.sub.2 SO.sub.4 + 2 g/l HNO.sub.3 150.degree. F. 90 30 P 3 3 g/l
H.sub.2 SO.sub.4 + 3 g/l HNO.sub.3 150.degree. F. 90 5 P 3 2 g/l
H.sub.2 SO.sub.4 + 2 g/l H.sub.3 PO.sub.4 120.degree. F. 100 10 P 4
3 g/l H.sub.2 SO.sub.4 + 3 g/l H.sub.3 PO.sub.4 120.degree. F. 100
10 P 4 4 g/l H.sub.2 SO.sub.4 + 0.01 g/l NH.sub.4 HF.sub.2
120.degree. F. 80 50 P 4 4 g/l H.sub.2 SO.sub.4 + 0.02 g/l NH.sub.4
HF.sub.2 120.degree. F. 50 10 P 4 4 g/l H.sub.2 SO.sub.4 + 0.04 g/l
NH.sub.4 HF.sub.2 120.degree. F. 20 0 G 2 4 g/l H.sub.2 SO.sub.4 +
0.05 g/l NH.sub.4 HF.sub.2 120.degree. F. 10 0 E 1 4 g/l H.sub.2
SO.sub.4 + 1 g/l anionic 120.degree. F. 0 0 E 1 surfactant + .02
g/l HF 10.0 g/l H.sub.2 SO.sub.4 + 1.0 g/l anionic 135.degree. F. 0
0 G 2 surfactant + 0.005 g/l HF 1.0 g/l H.sub.2 SO.sub.4 + 1.0 g/l
anionic 110.degree. F. 0 0 E 1 surfactant + 0.10 g/l HF
__________________________________________________________________________
EXAMPLE II
An aqueous acidic cleaning bath was prepared by adding 4.0 grams of
sulfuric acid, 0.02 grams of hydrofluoric acid, and 1.0 gram of an
anionic surfactant (Tergitol 08) to each one liter of water. The
temperature of the bath was elevated to and maintained at
120.degree. F. A fluoride specific ion electrode and a saturated
calomel reference electrode were coupled to a potentiometric meter
capable of discerning changes in electrode potential of .+-.1.0
millivolt. The electrodes were immersed into the bath and the meter
adjusted, by the zero offset control, to read on the center of the
scale.
Aluminum containers of 3004 alloy drawn into single piece
containers were sprayed with the prepared bath and the meter
readings became more positive. When the electrode potential reached
+3 millivolts from center scale, hydrofluoric acid additions were
made to restore the electrode potential to center scale. Electro
metric pH measurements, and sulfuric acid additions were made to
maintain the pH at 1.3 to 1.5.
The containers were observed to be water-break-free and bright in
appearance.
EXAMPLE III
An aqueous acidic cleaning bath was prepared by adding 4.0 grams of
sulfuric acid, 0.02 grams of hydrofluoric acid, and 1.0 gram of a
nonionic surfactant (Triton DF-16) to each one liter of water. The
temperature of the bath was elevated to and maintained at
120.degree. F. A fluoride specific ion electrode and a saturated
calomel reference electrode were coupled to a potentiometric meter
capable of discerning changes in electrode potential of .+-.1.0
millivolt. The electrodes were immersed into the bath and the meter
adjusted, the the zero offset control, to read on the center of the
scale.
Aluminum containers of 3004 alloy drawn into single piece
containers were sprayed with the prepared bath and the meter
readings became more positive. When the electrode potential reached
+5 millivolts from center scale, hydrofluoric acid additions were
made to restore the electrode potential to center scale. Electro
metric pH measurements, and sulfuric acid additions were made to
maintain the pH at about 1.2.
The containers were observed to be water-break-free and bright in
appearance.
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