Note: Descriptions are shown in the official language in which they were submitted.
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
COMPOSITION AND PROCESS FOR SEALING ANODIZED ALUMINUM
BACKGROUND OF THE INVENTION
This invention relates to a process for sealing anodically oxidized aluminum
and
aluminum alloy surfaces, so as to increase the resistance of the anodic oxide
film to ex-
ternal corrosive agents, and to a composition for use in the process of the
invention.
s More specifically, the invention provides an aqueous sealing composition
substantially
free of environmentally sensitive heavy metals.
Articles of aluminum or an aluminum alloy are typically subjected to an anodic
oxidation process to improve the hardness and corrosion resistance of the
surface of the
article. As used herein the term aluminum includes pure or substantially pure
aluminum
1o as well as alloys of aluminum containing, in general, at least about 50 %
by weight of
aluminum. Examples of other metals which may be present in such aluminum
alloys are
silicon, bismuth, copper, nickel, zinc, chromium, lead, iron, titanium,
manganese, and the
like. The anodic oxidation of an aluminum surface results in the formation of
a uniform,
translucent, highly porous aluminum oxide film. The anodic oxide film can also
serve an
i5 aesthetic or decorative function and may be clear, dyed with organic or
inorganic
substances, or electrolytically colored.
Generally, these anodic aluminum oxide films result from the passage of a
direct
electric current through an acidic electrolyte solution at temperatures
ranging from 0 to
32 °C. Typically, the acidic electrolyte solution will employ sulfuric
acid at concentrations
2o from 140 to 200 grams of sulfuric acid per liter of anodizing electrolyte,
this unit of
concentration being hereinafter applicable to any ingredient in any
composition and
being hereinafter usually abbreviated as "g/1".
Anodic oxidation of aluminum is intended to provide a protective coating or
film
of aluminum oxide on the aluminum surface. Although this anodic oxide layer is
more
25 resistant to corrosion than the untreated aluminum surface, the porous
structure of the
aluminum oxide layer renders it vulnerable to corrosion and degradation,
particularly to
that caused by external chemical agents. As a result, anodized aluminum oxide
films or
surfaces are commonly subjected to a process known as sealing. (It is
currently
theorized, but without any intent to limit this invention, that the sealing
process closes or
so fills the pores via hydration and/or precipitation of one or more
compounds.) Aluminum
articles treated in such a manner are generally valuable in a wide variety of
end use
applications, even those in which environmental conditions are severe. High
quality
sealed anodic aluminum oxide films should exhibit superior resistance to
corrosion and
1
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
degradation caused by most external chemical agents.
Prior art sealing processes can generally be divided into three categories:
hydro-
thermal sealing processes; mid-temperature sealing processes; and low
temperature
sealing processes.
s Hydrothermal sealing processes employ steam or boiling water to seal the
anodic
oxide coating. This process is believed to cause a hydration of the oxide
coating, which
results in the constriction of the surface pores. Although good quality sealed
films are
generally obtained, a disadvantage of this process is the cost of extremely
high energy
consumption associated with its operation.
io Mid-temperature sealing processes operate at temperatures between 76 and 93
°C. They generally employ, as the sealant compositions, aqueous
solutions of heavy
metal salts such as nickel or cobalt. Mid-temperature sealing processes enjoy
a signifi-
cant saving in energy consumption as compared to hydrothermal sealing
processes, but
present significant waste disposal problems in view of the presence of heavy
metals.
Such solutions often require expensive pretreatments prior to disposal.
Low temperature sealing processes also require the use of heavy metals. Such
processes typically employ nickel salts such as nickel fluoride and operate at
tempera-
tures of about 32 °C. In addition to waste disposal problems because of
the use of heavy
metal ions, low temperature sealing processes suffer from the disadvantage of
producing
2o a sealed anodic film having a very low crazing temperature.
U. S. Patent 5,411,607 ("the '607 patent"), the entire disclosure of which
except
for any part that may be inconsistent with any explicit statement herein is
hereby incor-
porated herein by reference, teaches what are believed to be the most
advantageous
mid-temperature processes yet in use, but experience since the application for
this
25 patent was filed has revealed some potential problems with the technology
taught in it:
The most generally practiced teachings of this patent can produce sealed
anodized films
that are susceptible to a generally unwanted yellowing when exposed to
sunlight or other
ultraviolet light. Furthermore, the sealing compositions as most commonly used
from the
teachings of the '607 patent can be susceptible to a deterioration in
performance from
so silicon compounds that tend to accumulate in the sealing baths during use.
The
deterioration in performance from accumulating silicon compounds can be
reversed to
a considerable extent by the addition of more of the type of organic smut
inhibitor taught
in the '607 patent, but it has been found that such increased concentrations
of the
preferred smut inhibitor taught in the examples of the '607 patent increase
the yellowing
35 tendency of the sealed coatings. The present invention is an improvement of
the
technology taught in the '607 patent that largely overcomes these deficiencies
of the
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
most common practice of the teachings of the '607 patent, while continuing to
provide
a process and composition for sealing anodized aluminum articles or surfaces
which has
relatively low energy costs, is environmentally friendly, and provides a
sealed anodic
aluminum oxide film of high quality, the aqueous sealing solution being
substantially free
of elements selected from the group consisting of the heavy metals and
phosphorus.
Except in the claims and the operating examples, or where otherwise expressly
indicated, all numerical quantities in this description indicating amounts of
material or
conditions of reaction and/or use are to be understood as modified by the word
"about"
in describing the broadest scope of the invention. Practice within the
numerical limits
io stated is generally preferred, however. Also, throughout this description
unless expressly
stated to the contrary: percent, "parts of", and ratio values are by weight;
the term
"polymer" includes oligomer; the description of a group or class of materials
as suitable
or preferred for a given purpose in connection with the invention implies that
mixtures of
any two or more of the members of the group or class are equally suitable or
preferred;
i5 description of constituents in chemical terms refers to the constituents at
the time of ad-
dition to any combination specified in the description, and does not
necessarily preclude
chemical interactions among the constituents of a mixture once mixed;
specification of
materials in ionic form implies the presence of sufficient counterions to
produce electrical
neutrality for the composition as a whole; any counterions thus implicitly
specified should
2o preferably be selected from among other constituents explicitly specified
in ionic form,
to the extent possible; otherwise such counterions may be freely selected,
except for
avoiding counterions that act adversely to an object of the invention; and the
term "mole"
and its variations means "gram-mole" and its variations and may be applied to
elemental,
ionic, hypothetical, unstable, and any other chemical species defined by
number and
25 type of atoms present, as well as to compounds with well defined molecules.
BRIEF SUMMARY OF THE INVENTION
A sealing composition according to the present invention comprises, preferably
consists essentially of, or more preferably consists of, water and the
following compon-
ents:
so (A) from 0.01 to 50 g/1 of lithium cations;
(B) a first organic smut inhibitor selected from molecules conforming to the
general
formula given in column 5 lines 35 through 40 of the '607 patent, wherein:
3
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
- Y represents a direct bond or a divalent moiety selected from the group
consisting of:
i H3 O O
-C-, -~-, -~-, -0-, and -S-;
CH3
- each of R, and R2, these being alternatively designated hereinafter as the
"hydrophobe moieties" of the smut inhibitors corresponding to said gener-
io al formula, independently represents hydrogen or a C5 - C,4 alkyl moiety,
with the proviso that R, and R2 are not both hydrogen;
- n is an integer from I to 4 inclusive; and
- X~ represents a counterion, such as H~ or an alkali metal cation; and
(C) a second organic smut inhibitor selected from molecules conforming to the
gen-
is eral formula given in column 5 lines 35 through 40 of the '607 patent,
wherein:
- each of Y, n, and X~ has the same meaning as for component (B); and
- each of R, and R2 independently represents hydrogen or a C,5 - C25 alkyl
moiety, with the proviso that R, and R2 are not both hydrogen;
and, optionally, one or more of the following components:
20 (D) a component of pH adjusting agent, buffering agent, or both adjusting
and buffer-
ing agent, that is not part of any of immediately previously recited
components
(A) through (C);
(E) a component of antifoam agent that is not part of any of immediately
previously
recited components (A) through (D); and
25 (F) a component of wetting agent that is not part of any of immediately
previously
recited components (A) through (E);
Various embodiments of the invention include working compositions for direct
use
in treating metals, concentrates from which such working compositions can be
prepared
by dilution with water, articles of manufacture including a surface contacted
with a
so composition according to the invention, and processes. A process according
to the in
vention in its most basic form requires only an operation of contacting an
anodically
oxidized aluminum surface with a sealing composition according to the
invention as
described above. Other operations, usually conventional in themselves, may be
performed before and/or after such contacting in an extended process according
to the
s5 invention.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
Anodized aluminum surfaces suitable for sealing according to the present inven-
4
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
tion include all of those obtainable by anodic oxidation processes that
produce an ano-
dized coating that is at least partially porous. For example, preferred
anodized aluminum
surfaces will generally be those resulting from the process of passing direct
electric
current through an acidic electrolyte solution with the aluminum surface
charged as the
s anode and a distinct counter electrode that is charged as the cathode.
Suitable acidic
electrolyte solutions are generally those containing sulfuric acid, oxalic
acid or sulfamic
acid. It will be appreciated by those skilled in the art that usually, prior
to immersion of
an aluminum article in the electrolyte solution, the article preferably will
be degreased,
washed, and optionally desmutted and/or deoxidized in a conventional manner.
The
1o characteristics of anodizing processes that are particularly preferred for
preparing
surfaces to be sealed according to the invention are set forth in the working
examples
below, but those skilled in the art will appreciate that it is not essential
to the practice of
the invention that the anodizing process be so limited.
Decorative anodized aluminum surfaces such as those which have been colored
i5 either electrolytically or with the use of organic and/or inorganic dyes
may also be sealed
with the use of the present invention. Suitable anodized aluminum oxide films
to be
sealed can be found on aluminum articles having a wide variety of shapes and
configura-
tions and will result from numerous manufacturing and processing means.
Illustrative
examples of suitable aluminum articles are plates, pipes, rods, extruded bars
with irreg-
2o ular or regular cross-sections, and articles formed by deep drawing and
pressing.
Suitable sources of the lithium ions are those lithium containing compounds
which, upon addition to water or an aqueous solution dissolve with
disassociation of the
lithium content into cations in the solution. Particularly suitable for use
herein are lithium
hydroxides and lithium salts. Illustrative examples of suitable sources of
lithium ions are
25 lithium acetate, lithium nitrate, lithium chloride, lithium carbonate,
lithium acid carbonate,
lithium oxide, lithium hydroxide, lithium bromate, and lithium oxalate.
Lithium acetate and
those compounds which are lithium acetate precursors are most preferred.
(Lithium ace-
tate precursors are compounds, such as lithium hydroxide and lithium oxide,
that can re-
act with acetic acid and/or precursors thereof, such as acetic anhydride, in
aqueous solu-
so tion to form lithium acetate and water.)
The sources) of lithium ions may be combined with generally available tap
water
provided that such water is substantially free from phosphate, sulfate, and
silicaceous
matter. (It has been found that, even in the most preferred compositions
according to the
invention, phosphate concentrations of less than 20 parts of phosphate per
million parts
s5 of total sealing solution, a concentration unit that may be used
hereinafter for any ingredi-
ent of any composition and is hereinafter usually abbreviated as "ppm", can
degrade
CA 02390994 2002-05-09
WO 01/34872 PCT/LTS00/30840
sealing quality, as can concentrations of silicaceous matter with a
stoichiometric equiva-
lent as silica that is greater than 90 ppm and/or concentrations of more than
4.1 parts of
sulfate per thousand parts of total composition, this concentration unit being
freely used
hereinafter for any ingredient of any composition and being hereinafter
usually abbre-
s viated as "ppt".) Accordingly, more preferably, the sources) of lithium ions
will be com-
bined with deionized water. Deionized water is commercially available and may
be
defined as water from which all or substantially all ionic constituents have
been removed,
usually by passage of the water successively through acid form cation exchange
resins
and alkali form anion exchange resins or through a mixture of acid form cation
exchange
1o resins and alkali form anion exchange resins. (It should be noted that,
because of the
very low ionization constant of silicic acid, this constituent and some of its
salts may not
be effectively removed by conventional ion exchange processes and instead may
be
concentrated in the deionized water, because at the time of contact with the
ion
exchange resin, the silicic acid or salt thereof is mostly in nonionic form.)
i5 The concentration of lithium ions in a sealing composition according to the
invention may be varied over quite a wide range with little or no variation in
technical
quality of the sealing obtained. More particularly, the concentration of
lithium ions in a
working sealing composition according to the invention preferably is at least,
with in-
creasing preference in the order given, 0.01, 0.05, 0.10, 0.15, 0.20, 0.22,
0.24, 0.26,
20 0.28, 0.30, 0.32, or 0.34 g/1 and independently preferably is not more
than, with
increasing preference in the order given, 20, 15, 10, 5.0, 4.0, or 3.0 g/1 and
for economy
more preferably is not more than, with increasing preference in the order
given, 2.5, 2.0,
1.8, 1.6, 1.4, 1.2, 1.00, 0.90, 0.80, 0.70, 0.60, 0.50, 0.45, or 0.40 g/1.
Each of surfactant components (B) and (C), independently for each and inde-
25 pendently for each preference stated, is preferably selected from molecules
that conform
to the general formula in column 5 lines 35 - 40 of the '607 patent when:
- n is 2 or 3, more preferably exactly 2;
- when n is at least 2, each aromatic ring in the general formula has at least
one
of the -S03 moieties bonded directly to said aromatic ring;
so - Y represents a dimethylmethylene moiety or an -~ moiety, more preferably
the
latter; and
- X~ represents an alkali metal cation, most preferably a sodium cation.
Additional individual preferences that are indicated below for components (B)
and (C)
separately are independent of these general preferences for both components,
and any
35 two or more of the general and the individual preferences may be combined
to result in
more particular preferences.
6
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
Surfactant component (B) with shorter alkyl substituent(s) preferably consists
of
molecules that conform to the general formula in column 5 lines 35 - 40 of the
'607
patent so that, independently for each preference stated, for the entire
component:
- all R, and R2 moieties that are alkyl moieties contain an average number of
car-
s bon atoms that has a value that is at least, with increasing preference in
the
order given, 6, 8, 10.0, 10.5, 11.0, 11.5, or 11.9 and independently
preferably is
not more than, with increasing preference in the order given, 13.5, 13.0,
12.5, or
12.1; and
- at least if all R, and R2 moieties that are alkyl moieties have an average
number
1o of carbon atoms that is at least one of:
-- not more than, with increasing preference in the order given, 10.5, 11.0,
11.5, or 11.9; and
-- not less than, with increasing preference in the order given, 14.0, 13.5,
13.0, or 12.5,
15 the number average of the number of branching carbon atoms, which are
defined
as carbon atoms directly bonded to at least three other carbon atoms, in each
of
said R, and R2 moieties that are not hydrogen atom moieties, is at least, with
in-
creasing preference in the order given, 1.0, 1.5, 2.0, 2.5, or 3Ø
Independently of its exact chemical nature, component (B) preferably is
present
2o in a working sealing composition according to the invention in a
concentration that is at
least, with increasing preference in the order given, 0.10, 0.20, 0.30, 0.40,
0.50, 0.60,
0.65, 0.70, 0.72, 0.75, 0.80, 0.85, 0.88, 0.90, 0.92, or 0.94 g/1 and
independently prefer-
ably is not more than, with increasing preference in the order given, 4.0,
3.5, 3.0, 2.5,
2.0, 1.5, 1.3, 1.1, or 1.02 g/1. If the concentration of component (B) is too
low, an
25 undesirable characteristic called "smutting", "smut", or "bloom" is likely
to occur on the
surface being sealed. These terms describe the deposition of hydrated aluminum
oxide
crystals on the surface of the anodic aluminum oxide film. Such smut or bloom
greatly
impairs the decorative or aesthetic appeal of anodized aluminum. The hydrated
aluminum oxide is easily degraded by even light abrasion or touching and is
particularly
so easily damaged by contact with human hands. Smut also interferes with
attempts to bond
smutted sealed anodized aluminum surfaces to other surfaces. Chemical and me-
chanical desmutting after-treatments are known in the art, but they introduce
undesirable
expense and may themselves adversely affect the overall quality of the sealed
anodized
aluminum film. If the concentration of component (B) is too high, smutting is
usually
35 prevented, but yellowing upon exposure to ultraviolet light becomes far
more likely, and
the amount of component (B) can also become an economic liability.
7
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
Surfactant component (C) with longer alkyl substituent(s) preferably consists
of
molecules selected from the group that conform to the general formula in
column 5 lines
35 - 40 of the '607 patent so that, independently for each preference stated,
for the
average of the entire component:
s - all R, and R2 moieties that are alkyl moieties contain an average number
of car-
bon atoms that is at least 16 and independently preferably is not more than,
with
increasing preference in the order given, 23, 21, 19, or 17; and
- all R, and R2 moieties that are alkyl moieties do not contain an average
number
of branching carbon atoms that is more than, with increasing preference in the
order given, 2.0, 1.0, or 0.1.
Independently of its exact chemical nature, component (C) preferably is
present
in a composition according to the invention in a concentration that is at
least, with in-
creasing preference in the order given, 0.05, 0.10, 0.15, 0.25, 0.35, 0.45,
0.50, 0.55,
0.60, 0.65, 0.70, or 0.75 g/1 and independently preferably is not more than,
with increas-
~5 ing preference in the order given, 4.5, 4.0, 3.5, 3.0, 2.5, 2.1, 1.8, 1.60,
1.50, 1.40, 0.90,
0.85, 0.82, or 0.79 g/1. If the concentration of component (C) is too low,
smutting is likely
to occur on the surface being sealed, while if the concentration of component
(C) is too
high, an excessive cost without any offsetting benefit will be incurred.
Independently of their actual values, the concentration of component (C)
prefer-
2o ably has a ratio to the concentration of component (B) in the same
composition
according to the invention that is at least, with increasing preference in the
order given,
0.1:1.00, 0.3:1.00, 0.5:1.00, 0.55:1.00, 0.60:1.00, 0.65:1.00, 0.68:1.00,
0.70:1.00,
0.72:1.00, or 0.74:1.00 and independently preferably is not more than, with
increasing
preference in the order given, 5.0:1.00, 4.0:1.00, 3.0:1.00, 2.5:1.00,
2.0:1.00, 1.8:1.00,
25 1.6:1.00, 1.4:1.00, 1.2:1.00, 1.00:1.00, 0.90:1.00, 0.85:1.00, or
0.80:1.00.
A working aqueous sealing composition according to the invention preferably
has
a pH value that is at least, with increasing preference in the order given,
1.0, 2.0, 3.0,
4.0, 4.5, 5.0, 5.3, 5.50, 5.60, 5.70, or 5.80 and independently preferably is
not more than,
with increasing preference in the order given, 9.5, 9.0, 8.5, 8.0, 7.5, 7.0,
6.5, 6.3, 6.20,
so 6.10, or 6.00. When the pH is either too low or too high, the protective
value of the
sealed anodized coating, as indicated by an acid dissolution test, will be
impaired. The
higher the concentration of silicaceous matter dissolved, dispersed, or both
dissolved
and dispersed in the working composition, the more easily the protective value
of the
coatings will be diminished by pH values outside the more preferred ranges.
s5 The preferred pH value is preferably stabilized by use of a buffer system
in a
working aqueous liquid composition according to the invention. Normally, the
preferred
8
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
buffer system consists of the anions of the salts) from which lithium cations
are sourced
to the aqueous liquid composition combined with the acids) corresponding to
those an-
ions. Accordingly, when lithium is sourced from lithium acetate as most
preferred, acetic
acid is also preferably present in the aqueous liquid composition according to
the inven-
tion in order to buffer the pH of the composition. If lithium cations are
provided to the
aqueous liquid composition by addition of lithium oxide or hydroxide, an
amount of acetic
acid that is more than sufficient to neutralize the oxide or hydroxide added
is preferably
also included in the aqueous liquid composition, in order to similarly
constitute an acetic
acid-acetate buffer system at the desired pH value. In either of these
instances, the ratio
~o of the molar concentration of unneutralized acetic acid to the molar
concentration of
acetate ions in the same composition preferably is at least, with increasing
preference
in the order given, 0.010:1.00, 0.020:1.00, 0.030:1.00, 0.040:1.00,
0.045:1.00,
0.050:1.00, or 0.055:1.00 and independently preferably is not more than, with
increasing
preference in the order given, 0.6:1.00, 0.4:1.00, 0.2:1.00, 0.100:1.00,
0.080:1.00,
~5 0.070:1.00, 0.065:1.00, or 0.060:1.00 If any adjustment of pH should be
required during
prolonged use of a composition according to the invention in a process
according to the
invention, adjustments may be made as needed with the use of acetic acid to
lower pH
or ammonium hydroxide to raise pH.
Often, optional components (E) and (F), wetting and antifoam agents, are not
2o needed in a composition according to the invention and when not needed are
preferably
omitted, at least for economy. If lack of wetting and/or excessive foam
generation should
be noted during a process according to the invention, those skilled in the art
will know
or will be able to determine with minimal experimentation what kinds of
wetting and
antifoam agents will overcome these problems without unacceptably interfering
with the
25 benefits of the invention. One suitable antifoam agent is FOAMBANT"~
antifoam from
Ultra Additives, Paterson, New Jersey, but many others are also suitable.
For varied reasons, some of which have been indicated above, it is preferred
that
several materials, including some that have been included in previous sealing
composi-
tions for anodized aluminum, should be omitted or at least minimized in
compositions
so according to the invention. More particularly, independently for each
preferably
minimized component listed below, a composition according to the invention
preferably
does not contain more than, with increasing preference in the order given, 1,
0.5, 0.2,
0.08, 0.05, 0.02, 0.008, 0.005, 0.002, 0.0008, 0.0005, 0.0002, 0.00008,
0.00005,
0.00002, 0.000008, 0.000005, or 0.000002 percent of any of the following: any
metal
s5 cations other than alkali metal cations; any anions that contain phosphorus
atoms; any
dispersed or dissolved substance that contains silicon atoms; sulfate anions;
and any
9
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
anions that contain fluorine atoms. (However, if optimum amounts of components
(B)
and (C) as described above are present, larger amounts of silicon atoms and
sulfate
anions may be tolerated without serious impairment of the results achieved.)
A concentrate make-up composition according to the invention preferably
contains all of the ingredients other than water desired in a working sealing
composition
according to the invention and therefore is by definition a "single package"
make-up
concentrate, because it can be converted to a working sealing composition by
dilution
with water only, except that some further pH adjustment may possibly be
required. In
order to increase the savings from supplying a concentrate instead of a
working
io composition and thereby avoiding transportation costs for water that can
usually be
added less expensively at the point of use, a single package make-up
concentrate
according to the invention preferably contains each ingredient as noted above
in a
concentration that is at least, with increasing preference in the order given,
2, 4, 8, 15,
20, 25, 30, 35, 40, or 45 times as great as one of the preferred
concentrations indicated
is above for the particular ingredient in a working composition. In order to
avoid phase
separation and/or other instability during shipment or storage, a make-up
concentrate
composition preferably does not contain any ingredient in a concentration that
is more
than, with increasing preference in the order given, 100, 75, 50, 40, or 35
times greater
than one of the preferred concentrations indicated above for the particular
ingredient in
2o a working composition.
As any particular volume of working composition is used, its ingredients will
be
depleted to some extent by incorporation into the sealed anodized coating
and/or by
mechanical drag-out. It has been found that components (B) and (C) as
described
above, along with component (E) if present, are consumed more rapidly than the
lithium
25 ions or buffering components. Accordingly, a replenisher concentrate
preferably
contains its surfactant components in a concentration with a higher ratio to
the lithium
ion concentration than in a preferred working sealing composition. More
particularly, the
ratio of the concentration of either of components (B) and (C) to the
concentration of
lithium ions in a replenisher concentrate preferably is at least, with
increasing preference
so in the order given, 1.2, 1.4, 1.6, 1.8, or 2.0 times higher than the ratio
of the
concentration of component (B) or (C) to the lithium ions concentration in the
initial
working sealing composition that is being replenished with a replenisher
concentrate.
Independently, the concentration of each of components (B) and (C) in a
replenisher
concentrate has one of the preferred ratios to the concentration of the same
component
s5 in the working sealing composition being replenished as have been already
described
above for the ratios of these ingredients in a single package make-up
concentrate to the
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
concentration of the same ingredient in a working sealing solution made up
from the
make-up concentrate. The degree of preference of various ratios as specified
for the
make-up concentrate also applies to the ratios for the replenisher
concentrate.
In a process according to the invention, anodized coatings formed on aluminum
are preferably contacted with the aqueous sealing composition by immersion of
the work
piece in a composition according to the invention that is maintained at a
temperature that
is at least, with increasing preference in the order given, 30, 40, 50, 60,
65, 70, 73, 76,
79, 81, 83, or 85 °C and independently preferably is not more than,
with increasing pref-
erence in the order given, 94, 92, 90, or 88 °C during the period of
immersion. The time
io of immersion or other contact of the anodized aluminum surface or article
with the aque-
ous sealing composition is a function of the thickness of the anodized
aluminum oxide
film. In general, an anodized aluminum coating to be sealed preferably will
remain in con-
tact with the sealing composition for a minimum of 4.0 minutes with an
additional 1.0
minute preferably added to this minimum for every 2.5 micrometres (hereinafter
usually
~s abbreviated as "Nm") of thickness of the anodized aluminum coating to be
sealed.
The practice of the invention may be further appreciated from the following,
non-
limiting operating examples and comparative examples, in which commercially
available
rectangular Type 6063 aluminum test panels with dimensions of 76 x 89
millimeters were
subjected to the following cleaning and anodization processes in the order
stated: Test
2o panels were initially cleaned by immersion in an aqueous solution
containing 50 g/1 of
NOVACLEAN~ 120 Cleaner Concentrate (commercially available from Henkel Surface
Technologies Division of Henkel Corporation, Madison Heights, Michigan, this
supplier
being hereinafter usually abbreviated as "HST") at a temperature of 66
°C for
approximately five minutes. Thus degreased panels were rinsed with tap water
at room
25 temperature (i.e., 18 - 23 °C), then etched at 66 °C by
immersion for approximately five
minutes in a solution containing 50 g/1 of NaOH and 2.0 % by volume of EA-
1010T'" etch
additive (from HST). Thus etched panels were next rinsed with tap water at
room
temperature, then were desmutted by immersion in NOVOX~ 320 desmutting product
(from HST) at a temperature of about 21 °C for one minute. The panels
were
ao subsequently rinsed with tap water at room temperature. The thus prepared
test panels
were anodized in an electrolyte solution in water of 180 g/1 of sulfuric acid
and 2.5 % of
ANOMAX~ 9000 hard coating additive (from HST). The anodizing electrolyte was
maintained at 21 °C while the panels were anodized with direct current
at a current
density of 1.9 amps per square decimeter for about 32 minutes to produce an
anodized
s5 coating thickness of 18 to 20 Nm. Anodized test panels as thus prepared
were sealed
as described in specific examples below.
11
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
The organic smut inhibitors, alternatively called "surfactants" below, that
were
used in these specific examples were all commercial products obtained from Dow
Chem-
ical, and their characteristics as described below are those reported in this
manufactur-
er's technical literature. Each of them has as its active ingredients
molecules that con-
s form to the general formula given in column 5 lines 35 through 40 of the
'607 patent
when: Y represents -O-; n is 2, and one of the sulfonyl groups is on each
aromatic ring;
R, is hydrogen in about half the molecules and is the same as RZ in the
remainder of the
molecules; and X~ represents a sodium cation. The major distinction among them
is the
chemical nature of the hydrophobe moieties, which are n-hexyl for DOW FAXT""
Hydro-
~o trope surfactant, n-decyl for DOWFAXT"' 3B2, "tetrapropylene" (believed to
be tetra-
methyl-1-octyl) for DOW FAXT"" 2A1, and n-hexadecyl for DOW FAXT"' 8390. Each
of the
surfactants contains from 35 to 47 % of its active ingredients in a solution
in water.
SPECIFIC EXAMPLE GROUP 1
In this group, the variable investigated was the concentration of lithium
cations,
15 which were provided to the composition according to the invention as
lithium acetate di-
hydrate. Each composition additionally contained 2.0 g/1 of DOWFAXT"' 2A1, 2.0
g/1 of
DOW FAXT"' 8390, and sufficient acetic acid to bring the solution to a pH
value of 5.9 at
85 °C, at which temperature it was maintained for 12 minutes of contact
with the ano-
dized test panels in order to seal them. After this period of sealing, the
panels were re-
2o moved from contact with the aqueous liquid composition according to the
invention,
rinsed with deionized water, and dried. The dried panels were then evaluated
visually
for smut and according to American Society for Testing and Materials Test
Methods
B136-84 for dye stain resistance and B680-80 for acid dissolution resistance,
for the last
of which results are reported in grams per square meter, hereinafter usually
abbreviated
25 as "g/m2", or in milligrams per square inch. The concentrations of lithium
acetate and the
results of the acid dissolution resistance test are shown in Table 1. In
addition to these
results, all of the sealed test panels prepared were completely free of smut
and passed
the dye stain resistance test. A value of 4.0 g/m2 or its equivalent of 2.6
milligrams per
square inch in the acid dissolution test is commercially acceptable. It is
therefore
so apparent that all of the working compositions in Table 1 under the process
conditions
used in this Group produced satisfactory sealing.
12
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
Table 1
Working Composition g/1 of Lithium Acetateg/m2 Lost in Acid
Number Dehydrate in the Dissolution Test
Working
Composition
1.1 2.5 1.98
1.2 5.0 2.08
1.3 10.0 2.14
1.4 15.0 2.08
1.5 20.0 1.95
SPECIFIC EXAMPLE GROUP 2
In this group, the pH value of the aqueous liquid sealing composition
according
to the invention was the independent variable studied. The panel test
preparation before
sealing was the same as for Group 1, and the sealing compositions contained
the same
s ingredients as for Group 1 except that: the concentration of lithium acetate
dehydrate was
7.5 g/1 in every instance; when needed to obtain high pH values, ammonium
hydroxide
was added to the composition to adjust the pH instead of acetic acid; for
values under
the column heading "With Silicate", each composition contained a concentration
of sodi-
um silicate that was stoichiometrically equivalent to 60 ppm of SiOZ added to
simulate
~o contamination by silicaceous matter during prolonged use of a sealing
composition; and
the pH values of the compositions were as shown in Table 2 below. The dye
stain
resistance and acid dissolution resistance tests values obtained are also
shown in Table
2. All of the compositions and processes shown in Table 2 produced sealed
surfaces
that were completely free of smut.
13
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
Table 2
CompositionpH of Dye Stain g/m2 Lost in Acid
Dissolution Test
Number CompositionResistance Without Silicate With Silicate
2.1 5.0 Pass 5.5 8.9
2.2 5.5 Pass 2.9 2.9
2.2 5.8 Pass 2.5 2.4
2.3 6.0 Pass 2.5 2.7
2.4 6.5 Pass 2.7 3.4
2.5 7.0 Pass 2.5 6.7
2.6 7.5 Pass 2.9 9.2
2.7 8.0 Pass 3.3 10.3
2.8 8.5 Pass 3.6 10.9
2.9 9.0 Fail 16 19
2.10 10.0 Fail 20 28
15 COMPARISON EXAMPLE GROUP 3
In this group, amounts of surfactant and of sodium metasilicate were independ-
ently varied, and acid dissolution test values and yellowing tendency of the
resulting
sealed specimens were quantitatively measured. The panel test preparation
before
sealing was the same as for Groups 1 and 2, and the sealing compositions
contained
2o the same ingredients as for Group 2 except that: the pH was constant at
5.9, the only
surfactant in the sealing composition was DOWFAXT"' 2A1, and the
concentrations of
surfactant and of added silicate, the latter being measured as its
stoichiometric equiva-
lent as silica, were as shown in Table 3. The value of "DE" shown in Table 3
was mea-
sured on the samples sealed without any silicate added to the sealing
composition and
25 is the value calculated according to American Society for Testing and
Materials ("ASTM")
procedure D2244-85 after exposure to ultraviolet light for 720 hours according
to ASTM
Procedure G53-88. Lower values are preferred over higher ones in this test,
and values
of 1.5 or greater are generally not commercially acceptable, because of the
danger of
yellowing. Thus, it is clear from the results in Table 3 that the
concentration of
so DOWFAXT"~ 2A1 should be limited to less than 6.0 g/1 whenever yellowing
tendencies
in the sealed coating are not acceptable.
14
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
Table 3
g/1 of DOW-Value from 0E
FAXTM 2A1 Acid Dissolution Value
in Test in Milligrams
Sealing per Square
Inch,
When the Sealing
Composition
Contained
"Silica" at
a Concentration
of:
Composition~ 1 ppm 20 40 ppm 60 80 ppm 100
ppm ppm ppm
0.0 4.0 17 19 24 30 36 0.78
2.0 0.63 0.96 1.80 7.0 24 28 0.82
4.0 0.60 1.17 0.76 3.91 6.4 8.6 1.44
6.0 0.78 1.03 0.68 1.36 1.28 1.44 1.84
8.0 0.78 0.71 0.81 1.32 1.53 1.76 2.3
10.0 0.73 0.74 0.83 1.30 1.83 1.80 2.9
COMPARISON EXAMPLE GROUP 4
In this group the independent variables were the chemical structure of the sur-
25 factant used and the concentration of sodium metasilicate, measured as its
stoichiometric equivalent as silica, in the sealing compositions. All other
factors were the
same as for Group 3, except that the surfactant used was varied as shown in
Table 4,
but its concentration was always 6.0 g/1. Results are shown in Table 4 below.
Table 4
Chemical Nature of Value DE
Hydro- from
Acid
Dissolution
Test
in
Milligrams
per
phobe Alkyl Moieties Square Value
of Inch,
When
the
Sealing
Composition
Contained
Surfactant in Sealing"Silica"
Composi- at
a Concentration
of:
tion ~ 1 20 40 60 80 100
ppm ppm ppm ppm ppm
ppm
C6 straight 2.0 2.2 2.2 2.3 2.3 26 1.78
C,o straight 1.06 1.40 1.39 1.84 4.1 6.14 2.7
C,Z branched 0.78 1.03 1.36 1.36 1.2 1.44 1.84
C,6 straight 2.4 3.5 4.6 10.6 14.5 18.4 0.73
The values in Table 4 indicate that at this relatively high concentration,
only the
surfactant with the highest number of carbon atoms in its hydrophobe moieties
has good
yellowing resistance.
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
COMPARISON EXAMPLE GROUP 5
This group was substantially identical to Group 3, except that the surfactant
used
was DOWFAXT"" 8390, with molecules having straight chain hexadecyl hydrophobe
moi-
eties, instead of DOWFAXT"' 2A1. The results are shown in Table 5 below. The
values
in Table 5 show that this surfactant is much less effective at reducing the
acid dissolution
value than is the surfactant used in Group 3. However, the surfactant in this
group also
does not promote yellowing nearly as much as the surfactant used in Group 3.
Table 5
g/1 of DOW- Value 0E Value
FAXTM 8390 from
in Acid
Sealing Dissolution
Test
in Milligrams
per Square
Inch,
When
the
Sealing
Composition
Contained
Silica
at a
Concentration
of:
Composition ~ 1 ppm 10 ppm 20 ppm 30 ppm
0.0 4.0 5.5 16.9 24 0.52
2.0 2.7 1.59 1.74 10.5 0.73
4.0 2.8 2.0 2.0 3.7 0.57
6.0 2.3 2.4 3.4 6.0 0.73
8.0 2.5 2.2 3.1 4.5 0.42
10.0 2.4 2.4 3.5 4.6 0.58
COMPARISON EXAMPLE GROUP 6
This group was like Group 4, except that the amount of surfactant in each
instance was 4.0 g/1 instead of 6.0 g/1 as in Group 4, and the simulated
contaminant
added to most of the sealing compositions was sulfate ions (added as sodium
sulfate)
s instead of silica. Results are shown in Table 6 below.
The results in Table 6 show that the surfactant with branched hydrophobe moie-
ties is more tolerant of sulfate impurities, as it is of silica impurities,
but when used alone
at 4.0 g/1 it does not give quite enough resistance to yellowing.
EXAMPLE GROUP 7
io In this group, two different surfactants were combined. Each sealing
composition
tested contained 2.0 g/1 of DOW FAXT"' 8390 and 2.0 g/1 of another one of the
surfactants
used in the previous groups, the specific surfactant being specified in Table
7 below.
Varying amounts of sulfate as simulated contamination were added as in Group
6, and
16
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
Table 6
Chemical Value 0E
from
Acid
Dissolution
Test
in
Milligrams
per
Square
Inch,
When
Nature the Value
of Sealing
Composition
Contained
Sulfate
at
a
Concentration
of:
Hydrophobe
Alkyl Moieties
of Surfactant< 1 0.50 1.0 1.5 2.0 2.5 3.0 4.0
ppt ppt ppt ppt ppt ppt
in SealingPPm ppt
Composition
C6 straight1.6 14.8 16.3 16.7 13.7 17.0 13.6 18.4 1.40
C,o straight1.37 1.73 3.4 2.7 5.2 4.8 4.8 5.5 2.7
C,2 branched1.07 2.2 1.94 1.98 2.5 2.9 2.2 4.0 1.60
C,6 straight2.8 8.9 13.9 9.6 12.0 16.6 16.9 17.0 0.67
all other conditions were as specified for that Group. Results are shown in
Table 7 be-
low. In addition to these results, the DE value was measured for the sealed
coating re-
sulting from sealing with the "uncontaminated" sealing composition with each
type of sec-
ond surfactant, and in all instances the value was less than 1.0 and therefore
satisfac-
tory. The results in Table 7 indicate that the combination of DOW FAXT"" 2A1
and DOW-
FAXT"~ 8390 produces better sealing quality at every level of sulfate
concentration tested
than does either of the other combinations of surfactants tested, and, as
already noted,
the yellowing resistance of this combination is also fully acceptable.
Table 7
ConcentrationValue from Acid
of Dissolution
Sulfate Test in Milligrams
in Seal- per Square
ing CompositionInch,
When the Sealing
Composition
Contained the
Sulfate Concentration
Specified at
Left and the
Second Surfactant
was:
in Parts DOWFAXTM Hydro-DOWFAXTM 3B2 DOWFAXTM 2A1
per trope SurfactantSurfactant Surfactant
Thousand
< 0.01 3.1 2.4 2.0
0.50 4.0 3.4 2.2
1.0 6.4 4.1 2.3
1.5 4.6 3.0 2.2
2.0 7.3 3.1 2.4
2.5 8.4 3.1 2.4
3.0 9.4 3.1 2.2
4.0 7.9 3.9 2.3
5.0 10.2 4.4 2.5
6.0 13.1 7.1 2.4
7.0 15.2 9.7 3.8
17
CA 02390994 2002-05-09
WO 01/34872 PCT/US00/30840
EXAMPLE GROUP $
Conditions for this group are substantially identical to those for Group 7,
except
that the simulated contaminant added to the sealing compositions was again
sodium
metasilicate, measured as its stoichiometric equivalent as silica, instead of
sulfate, and
3.0 instead of 2.0 g/1 of each surfactant were present in the sealing
composition.
Specific values and results are shown in Table 8.
In addition to the results shown in Table 8, the DE values were measured for
the
sealed coatings formed with the "uncontaminated" sealing compositions of each
type
used in this Group. The DE value was < 1.2 for either DOWFAXT"' Hydrotrope
1o Surfactant or DOWFAXT"" 2A1 Surfactant as the second surfactant and was <
1.5 and
therefore acceptable for DOWFAXT"~ 3B2 Surfactant as the second surfactant.
Therefore, in this Group as well as in Group 7, the same combination of
surfactants
achieved the best results in the acid dissolution test, was satisfactory in
yellowing
resistance, and was highly tolerant of contamination.
Table 8
ConcentrationValue from Acid
of "Silica" Dissolution
in Test in Milligrams
Sealing per Square
Inch,
When the Sealing
Composition
Contained the
"Silica" Concentration
Specified at
Left and the
Second Surfactant
was:
2o Composition DOWFAXTM Hydro-DOWFAXTM 3B2 DOWFAXTM 2A1
in trope SurfactantSurfactant Surfactant
Parts per
Million
< 1 1.6 1.2 1.2
10 1.8 1.5 1.3
20 2.1 1.8 1.6
2.1 1.9 1.6
3.7 2.6 1.3
4.1 3.2 1.8
5.1 3.0 1.7
so 70 Not measured Not measured 1.4
80 Not measured Not measured 2.0
90 Not measured Not measured 2.1
100 Not measured Not measured 3.2
18
