Note: Descriptions are shown in the official language in which they were submitted.
1~7~45
COAq`ING SOLUTION FOR METAL SURFACES
,, _ .
Field of the Invention
This invention relates to the application to metal
surfaces of coatings which are corrosion resistant and to
which overlying coatings such as those formed from paints,
inks, and lacquers adhere ti~htly. ,~ore particularly, this
invention relates to acid c aqueous coating solutions which
are free of toxic materials such as chromates and ~erricyanide,
and which form the af~rementioned types of coatings OII
aluminum surfaces.
.
It is known to coat aluminum surfaces with aqueous
coatings ~olutions that are ~ffective in forming thereon
coatings which are corrosion resistant to thereby protect
the surface from degradatian due to attack by corrosive
materials. In general, the coatings formed from such
coatings solutions should also have properties such that
overlying coatings which are applied thereto adhere tightly
and strongly. Such overlying coatings are decorative or
functional in nature and are formed from materials such as
paints, lacguers, inks, etc. (hereinafter referred to as
"siccative coatings").
Certain aspects of the present invention will be
described in connection with the coating of aluminum cans.
The invention has, nevertheless, broader applicability.
' ' .
~,
~74~4S
Corrosion resistant coatings which are applied to aluminum
cans should be uniformly clear and colorless so that the
coated cans have the bright shiny natural appearance of the
underlying aluminum. This bright shiny natural appearance is
desired in the final product even thou~h portions of the can
may be covered with overlying siccative coatings~ (It is
noted that there are other aluminum coating operations in which
it is desired that the corrosion resistant and adherent coating
imparts to the aluminum surface a colored appearance, for
example a yellowish to green tint. ~owever, this is not
generally desired when coating aluminum cans~) The corrosion
resistant coatings should also have properties such that the
overlying coatings, which are decorative or functional in
nature, adhere tigIltly and strongly thereto.
... . . ..
Another property that coated aluminum cans should have
is the ability to resist discoloration when the coated can
is subjected to moderately hot water, for example, water
having a temperature within the range o~ about 140F to about
170P. This occurs in operations referred to in industry as
"Pasteurization" of the cans. This treatment has a tendency
to cause an uncoated or an inadequately coated aluminum surface
to blacken or otherwise discolor thereby leaving the can with
an unattractive appearance. The term "corrosion resistance"
is used herein, unless otherwise specifically stated, to mean
,
,
, -2-
945
. .
that the coated surface resists blackening or other discolor-
ation when exposed to the aforementioned hot water or boiling
water treatment. Such a coating will be referred to herein-
after as a "corrosion-resistant coating".
A further property that is desirable in coated aluminum,
cans is the ability of such cans to undergo a simple test to
confirm the presence of such ccating. ~his property allows
can manufactures to randomly sample cans from their line
and by means of such test determine that the clear and
colorless coating is actually present on the cans. One such
test conventionally employed in the can industry is known as
the "muffle test".
Coating solutions are p,resently ava~ilable which form
on aluminum surfaces uniformly clear and colorless coatings.
One of the most widely used coating solutions, which forms
such coatings, contains chromic acid, phosphoric acid and
hydxofluoric acid. In recent years, however, there has
been an industry-wide switch from hexavalent chromium-based
coating compositions to coating compositions which do not
contain this material, the use of which creates, in general,
waste disposal problems.
This invention relates to the provision of an a~ueous
coating solution which does not require the use of hexavalent
chromium or similarly toxic materials, and which is capable
--3--
~1'74~4S
of forming a clear and colorless, corrosion-reSistant coating
on an aluminum surface, which coating excellently adheres
to overlying, siccative coatings.
PEPOR$ED DEVELOPMENTS
Recent developments in the industry are exe~plified
by the disclosures of the following: pu~lished UK Patent
Application GB 2,014,617 A; U.S. Patent Nos. 4~107r334
3,9~4,936; and 4,148,670, the last two mentioned being
assigned to the same assignee as the present developmen~.
Compositions which are the subject of the aforementioned
are described as being capable of forming non-chromate
coatings on aluminum surfaces and each is acidic and includes,
as essential ingredients, a fluoride-containing compound and
variously either a zirconium-,titanium-,or hafnium-containing
compound. Phosphate is described as an additional essential
constituent o the composition of the '670 patent, while a
polyhydroxy compound having six or fewei~ carbon atoms is
described as an optional ingredient. Both phosphate and
tannin are described as additional essential constituents
of the composition of the '334 patent.
The presence of phosphate in the solution is said to
contribute to the corrosion resistance and adherent
properties of the coating, and to allow the coating to
undergo the so-called "muffle test'' which may be used to
49~S
.
confirm the presence of the coating on an aluminum surface.
However, phosphate has been found to cause a decrease in
the adhesion of certain water-borne siccative coatings, and
thus it would be desirable to produce a coating in which
phosphate is not an essential ingredient.
BRIEF DESCRIPTION OF THE I~7ENTION
In accordance with the present invention there is
provided an acidic aqueous coating solution that is capable
of forming a non-chromate, clear ana colorless, corrosion-
resistant coating on an aluminum surface and which solution
contains at leàst about 0.5 x 10 3 mole/liter of a metal
selected from the group consisting of zirconium, hafnium,
titanium, and mixtures thereof, fluoride in an amount at least
sufficient to combine with all of said metal, and characterized
in that it contains one or more of the following organic
compounds: at least about 10 ppm of a surfactant or at least
about 0.025 x 10 3 mjl of a polyhydroxy compound having no
more than 7 carbon atoms or a mixture thereof, said solution
being free of phosphate and boron when the or~anic compound
is the polyhydroxy compound.
The acidic aqueous coating solution of the invention can
be used to treat a bright shiny aluminum surface in a manner
such that the bright shiny appearance of the surface is not
changed, while forming on the surface a uniformly colorless and
clear coating which exhibits excellent corrosion resistance and
to which overlying siccative coatings adhere tightly.
. ' , .
4945
The coating solutions of the present invention are capable
of effectively forming the aforementioned type o coatings on
an aluminum surface in the absence of toxic materials and
materials of the type which create waste disposal problems,
including, for example, hexavalent chromium and elements such
as manganese, iron, cobalt, nickel, molybdenum and tungsten,
and also materials such as ferricyanide and ferrocyanide.
Accordingly, it is not necessary to add to the coating solution
of the present invention materials, which if added, would
mandate that effluents comprising the solution be treated
specially before the effluent is discharged to the environment
or to a sewage disposal plant.
Several of the advantages which flow from the use of
the present invention relate to the use of water-based compo-
~lstions from which there aré forme'd the siccative coatings
that ~overlie coatings formed from the composition of the
present invention. By way of background, it is noted that
there has been a relatively recent trend in the industry away
from the use of organic solvent-based coating compositions
and to the use of watér-based coating compositions. Industry
experience has shown that coatings formed from water-based
compositions do not tend to adhere as well to underlying coat-
ings of the prior art Zr, Ti, or Hf type as coatings formed
from organic solvent-based compositions. For example,
siccative coatings formed from water-based compositions
do not tend to adhere as well to underlying coatings formed
from the phosphate-containing compositions described'in afore-
mentioned U.S. Patent No. 4,148,670 as those formed from '
--6--
`"` ~17494S
.
organic solvent-based compositions. The compositions of the
present invention can be use~ to form on aluminum surfaces
coatings that provide an excellent adherent base or
siccative coatings formed from water-based compositions.
It has been observed that the corrosion resistance of
coatings formed from acidic aqueous coating solutions of the
invention in which the polyhydroxy compound is the organic
compound may tend to vary, depending on the type of water
used in preparing such compositions. The corrosion resistance
properties are better when the coatings are formed from com-
positions prepared from hard water than when they are formed
from compositions prepared from soft water. As wili be
described more fully below, it appears that the relatively
low calcium concentration in soft water affects adversely
... . . . . .
the corrosion resistant properties of the coatings. To
state it otherwise, the relatively high concentration of
calcium in hard water improves the corrosion resistance of
the coatings. ~his variatio in coating resistance with
variation in water hardness is not expexienced when the
5urfactant or the mixture of the surfactant and t~e poly-
hydroxy compound is the organic compound in the aqueous
acidic coating solutions of the present invention.
The term "surfactant" is used herein to mean a material
which when used in a small amount is capable of reducing
markedly the surface tension of water. For example, the presence
of as little as 2 ppm of surfactant dissolved in water can
9'~5
reduce the surface tension of water by more than one-third
of its normal value. Of the various classes of surfactants
that can be used (anionic, cationic, nonionic and amphoteric),
the use of a nonionic surfactant is preferred in accordance
with the present invention.
Detailed Description of the Invention
The coating solution of the present invention can be
used to coat surfaces of pure aluminum or alloys of
aluminum, for example, aluminum alloys containing minor
amounts of metals such as, for example, magnesium, manganese,
copper and silicon. Presently, the most popular alloy used
in the aluminum can industry is aluminum alloy 3004. It is
believed that one of the widest uses of the coating solution
of the present invention will be the coating of aluminum
suxfaces which have a bright shiny appearance. Aluminum
cans and aluminum strip are examples of articles that can
be treated effectively with the composition of this
invention.
The acidic aqueous coating solution can be prepared
from a variety of compounds which contain the aforementioned
essential ingredients (a metal selected from the group
consisting of titanium, zirconium and hafnium compounds and
mixtures thereof, a fluoride compound, and an organic compound
selected from the group consisting of a polyhydroxy compound
having no more than 7 carbon atoms, a surfactant, and a mixture
li~49~5
of said polyhydroxy compound and said surfactant) and which
are soluble in the solution. As to the source of the zirconium,
titanium, or hafnium, there can be used soluble fluozirconate,
fluotitanate or fluohafnate compounds such as, for example,
acids ~fluozirconic, fluotitanic, and fluohafnio) thereof
and ammonium and alkali metal fluozirccnates, fluotitanates,
and fluohafnates. The coating solution can be prepared also
from metallic fluorides such as zirconium fluoride ~ZrF4),
titanium fluoride (TiF3, TiF4), and hafnium fluoride (HfF4).
In addition, the coating solutions can be prepared from a
mixture of soluble compounds, one of which contains zirconium,
titanium, or hafnium, and the other of which contains fluoride.
Examples of such compounds are water soluble salts comprising
nitrates and sulfates of Zr, Ti or Hf (for example, zirconium
nitrate, zirconium sulfate, titanium (iv) sulfate, hafnium
.. , .,.~- .
nitrate), and hydrofluoric acid and water soluble salts
thereof, for example, ammonium and alkali metal salts.
Satisfactory coatings can be formed from coating solutions
D a~-t~ng as little as ab~ut 0.5 x 10 3 mDle/liter ("m/l") of either
Ti, or Hf (about 0.05 g/l of Zr, about 0.02 g/l of Ti, and
about 0.09 g/l of Hf). When utilizing a mixture of one or
more of Zr, Ti or Hf, the total of the amounts of the metals
should be at least about 0.5 x 10 m/l. However, as will be
explained below, greater amounts of these ingredients may be
required to produce satisfactory coatings depending on other
parameters of the coating process.
_9_ ,
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1~74945
zirconium, titanium, or hafnium can be used in amounts
up to their solubility limits in the acidic aqueous coating
solution. The solubility limits of the inyredients will
depend on other parameter3 of the coating solution, including
particularly, the acidity of the coating solution, the amount
of fluoride in the coating solution, and the amounts of optional
ingredients that mi~ht be used. These parameters should be
controlled so that the formation of zirconium, titanium, or
hafnium precipitate is avoided. The formation of such precip-
itate is undesirable for several reasons. Precipitation depletes
the amounts of the ingredients. Also, the deposition on the
coated aluminum surface of precipitate can adversely affect
the coating properties. In addition, the formation and
accumulation of any type o precipitate can tend to interfere
with the application of the coating solution. For example,
~: . .... .
it can clog spray nozzles. If precipitation is encountered
in a specific application, the pH of the coating sol~tion can
be lowexed, and/or the amount of fluoride can be increased.
As to the fluoride concentration, the minimum concentration
should be that which is sufficient to combine with all of the
zirconium, titanium, or hafnium to form a soluble complex
therewith, for example, a fluozirconate, fluotitanate, or
fluohafnate. Accordingly, the minimum amount of fluoride
is dependent on the amount o zirconium, titanium, or hafnium
in the solution. In general, at least about 4 moles of fluoride
per mole of Zr, Ti or Hf is necessary to prevent precipitation
of such metals. Preferably, at least about six moles of
fluoride are employed per mole of Zr, Ti or Hf.
,
--10--
11749~5
In situations wherein the coating solution is recycled
or a bath of the solution is used continuously, there is a
build-up in concentration of the aluminum dissolved by the
solution,~hich build-up may adversely affect the coating
process. Therefore, the coating solution should contain
an amount of fluoride sufficient to complex the dissolved
aluminum.
Thus, from a practical standpoint, the coating solutio~
should contain, when operating on an industrial scale, an
excess of fluoride, that is, an amount above that complexed
with aluminum and any other constituents in the solution that
form complexes with the fluoride. Such excess fluoride is
referred to herein as "availa~le fluoride" and the means for
calculation thereo is well known in the art. A coating
.;:. . . .
~olution which contains available fluoride is one in which
fluoride is available to complex with aluminum. In order to
avoid undue etching of the aluminum surface which tends to
produce a aull and frosty surface and to avoid adverse
affeats on corrosion resistance and adherent properties of
the coating as well as precipitation of calcium or other such
ions present in the solution, it is recommended that the
available fluoride concentration be no greater than about
26.3 x 10 3 mole/liter, or no greater than about 500 ppm.
Any material which is soluble in the coating solution,
which is a source of fluoride capable of complexing aluminum
and which does not contain a constituent which adversely
~'74945
affects the coating process can be used. If fluorlde i5
added as a complex fluoride of titanium, zirconium, or hafnium,
however, there should be added to the solution another
material such as HF, salts thereof, NH4F-HF, alkali metal
bifluorides, H2SiF6 or HBF4, which is a source of fluoride
for complexing the aluminum that builds up during continuous
use. HF and ~BF4 are particularly preferred sources o~ fluoride.
As mentioned above, it is preferred that the surfactant
for use in the present invention be selected from the nonionic
class of surfactants. Although in some cases noticeable
improvements will be observed when using about 10 ppm of sur-
factant, it is preferred to use the surfactant in an amount of
about 20 to about 100 ppm. Higher amounts, for example, up to
about 500 ppm, can be used, but in general, little or no
additional improvements are realized at higher concentrations.
.
As regards the polyhydroxy compound, any water soluble
polyhydroxy compound having no more than seven carbon atoms
or any compound soluble in the coating solution which when
dissolved th~n yields polyhydroxy compounds having seven or fewer
carbon atoms and which does not interfere with the ability
of the coating solution to coat or provide coatings having
the desired corrosion resistance and paint adherence may be
used. Examples of such compounds include gluconic acid, salts
of gluconic acid, sodium glucoheptonate, sorbitol, mannitol,
dextrose, ethylene glycol, and glycerine. Particularly preferred
polyhydroxy compounds are gluconic acid and alkali metal and
9'~S
ammonium salts thereof~ Any compound soluble in the coating
solution which yields gluconate and/or gluconic acid may be
used. Examples of such compounds are stable gluconolactones
such as glucono-delta-lactone and glucono-gamma-lactone.
It has been found that the use of the polyhydroxy compound
in the coating solution allows the user to conduct a simple
test to confirm the presence of the coating on the aluminum
surface even when the solution is free of phosphate. In an
industrial operation which can involve the treatment of vast
quantities of aluminum in a relatively shoxt time, it is
helpful to have a simple test to confirm that the coating
solution is forming a coating since the coating is not visible
to the eye. An unnoticed change in the operating parameters
of a bath of the coating solution which renders it ineffective
~, , .................. .. .~
may take place as a result of mechanical or human failure.
For example, improper replenishment of the coating solution
may go unnoticed.
.
It has been found that an aluminum surface coated with
such a composition of the present invention containing the
polyhydroxy compound of the invention and no phosphate changes
in color varying from light golden brown to darker shades of
brown or purple when subjected to a relatively high temperature
for a relatively short period of time ! for example, 900F for
S minutes. This test, referred to herein as the "muffle test",
can be used to randomly sample treated aluminum 9urfaces to
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~1749~5
determine whether or not the coating solution is depositing
on the aluminum surface. If the coating is not being
deposited, the aluminum surface has a dull greyish appearance
after the muffle test. The ability of such surfaces to
successfully undergo this test is quite surprising as
heretofore it had been believed that the presence of phosphate
was necessary to obtain a positive test.
Another advantage derived from the polyhydroxy compound,
and one also experienced with the surfactant, is that it en-
~lances the ability of coatings formed from coating solutions
containing this ingredient to withstand blackening or other
discoloration for a period of at least 5 minutes and up to as
long as 15 minutes when subjected to water having a temperature
within the range of about 140F to about 170~F. As noted
above, aluminum cans are sometimes treated in this manner
when subjected to so-called "pasteurization" procedures.
It has been found also that the use of the polyhydroxy
compound contributes to the corrosion resistance and adherent
properties of the coatings, particularly coatings formed from
a coating solution having a pH below about 3~5. In addition,
it has been found that overlying siccative coatings, particularly
water-borne coatings, adhere very well to coatings which
contain polyhydroxy compounds. While organic-borne siccative
coatings adhere well to coatings containing phosphates, certain
water-borne coatings have not been found to adhere nearly as
well to such coatings.
11749~5
Coated aluminum cans having a high level of water stain
resistance and capable of discoloring when subjected to the
aforementioned muffle test have been produced from coating
compositions containing as little as about 0.025 x 10 3
mole/liter of the polyhydroxy compound. Preferably, such
coating compositions contain from about 0.3 x 10 mole/liter
to about 1.75 x 10 3 mole/iiter of the polyhydroxy compound.
Higher amounts, for example, up to about 2.5 x 10 mole/liter,
can be used, but in general, little or no additional improve-
ments are realized at higher concentrations.
.
When the polyhydroxy compound is employed in the solutions
of the present invention along with the surfactant, it is
recommended tnat at least about 40 ppm of the polyhydroxy
compound be used. Although higher amounts can be used, it is
recommended that the polyhydroxy compound be present in an
amaunt no greater than about 1000 ppm. Preferably about 40
to about 400 ppm of the polyhydroxy compound are used~
The pH of the coating solution can vary over a wide range,
for example, about 1.5 to about S. Improvements in corrosion
resistance attributed to the surfactant, when present in the
solutions of the present invention, are observed particularly
at a pH within the range of about 3.5 to about 4.5. Improve-
ments in corrosion resistance attributed to the polyhydroxy
compound, when present in the solutions of the present invention,
-15-
~1749~5
.
are observed particularly at a pH within the range of about
3.0 to about 5.0, and preferably, a pH within the range of a~out
3.0 to about 4.0 is used. The p~ of the solution may be adjusted
by using appropriate amounts of nitric acid or ammonium
hydroxide. Although nitric acid and ammonium hydroxide are
recommended as pH adjusters, any acid or base which will
not interfere with the coating process can be used. For
example, perchloric acid or sul~uric acid can be used.
The coating solution of the present invention should be
free of chromium, iron cyanides, and any materials that form
in the solution solids which tend to precipitate.
Examples of other materials which can be optionally
added to the coating solution of the present invention are
, . . . .
those which have been reported heretofore as being useful in
Zr, Ti, or Hf and fluoride-containing compositions For
example, aforementioned U.S. Patent No. 3,964,936 discloses
the use of materials which are a source of boron in an
amount of at least about 10 ppm and ranging up to about 200 ppm.
When a boron compound is added to the acidic aqueous coating
solutions of the present invention which contain surfactant,
it is particularly preferred that the boron compound be added
as boric acid in the aforementioned amounts. Boron compounds
are not added to the solutions of the present invention that do
not contain the surfactant~ Tannin is another optional ingredient
that can be added to the solution in concentrations of at least
about 25 ppm and ranging up to about 10 g/l (see U.S. Patent
No. 4,017,334 and U.K. Patent Application GB 2,014,617).
-16-
ll'~g9~5
When using organic solvent-based coating compositions to
form the overlying siccative coating, the solution of the present
invention can Optionally include phosphate in an amount of
about 10 ppm to about 1000 ppm, as described in U.S. Patent
No. 4,148,670, except when the solution contains the poly-
hydroxy compound and does not contain the surfactant.
Still other materials which can be optionally added to
the coating solution of the present invention are various
.
other acids including, for example, glutaric, ascorbic, maleic,
and salicylic. Such acids can be used in amounts of at least
about 5 ppm and preferably within the range of about 100 to
about 500 ppm to realize various advantages, including improving
the adhesive properties of coatings formed from the solution.
.
Amount xanges for ingredients comprising the composition
of the present invention have been described above. Consider-
ations should be taken into account in formulating specific
compositions for spécific applications while working within
the aorementioned ranges. When operating at a relatively
high pH, relatively small amounts of zirconium, titanium and/or
hafnium should be used to deter precipitation. When contacting
the aluminum surface with the coating solution for a relativeiy
short time, relatively high amounts of the aforementioned
metals should be used. Similarly, when the temperature of
contact between the coating solution and the aluminum $urface
is relatively low, relatively high amounts of ingredients
should be used.
-17-
9~5
One preferred embodiment of the present invention ~herein-
after "preferred embodiment A") has a pH within the range of
about 3.4 to about 4 and contains:
Approximate Concentration
Ingredient in Moles~Liter
Zr 0.5 x 10 3 to 1.75 x 10 3
Polyhydroxy Compound 0.3 x 10 3 to 1.75 x 10 3
Available Fluoride -0.5 x 10 3 to 2r5 x 10 3
The preferred source of Zr in preferred em~odiment A is
ammonium fluozirconate, and the preferred polyhydroxy compound
is gluconic acid. Preferably hydrofluoric acid is used as
the source of available fluoridej and nitric acid is used
to adjust the pH.
When hafnium is added to preferred embodiment A, it is
preferably added in an amount of from about 0.5 x 10 mole~liter
to about 1.75 x 10 3 moles/liter. The preferred source of
hafnium i5 HfF4. Other preferred ingredients and amounts
thereof which may be employed in the preferred Zr-containing
solution of preferred embodiment A have been previously desaribed.
.
Another preferred embodiment of the present invention
~hereinafter "preferred embodiment B") has a pH within the
range of about 3.5 to about 4.5 and contains about 0.75 x 10 3
to about 2 x 10 3 m/l of zirconium and about 10 ppm to about
500 ppm of surfactant and, most preferably,a pH within the
range of about 3.7 to about 4.3 and contains 1 x 10 3 to
-18-
~i749~5 .
about 1.75 x 10 3 m/l of zixconium and about 20 to about 100 ppm
of surfactant, each of the aforementioned containing enough
fluoride to complex all of the Zr and the dissolved aluminum
present in the solution.
The preferred source of both Zr and fluoride in the
make-up composition of preferred embodiment B is fluozirconic
acid and nitric acid is preferably used to adjust the pH.
The coating solution of the present invention can be
prepared con~eniently by diluting an aqueous concentrate
of the ingredients with an appropriate amount of water. For
example, with regard to preferred embodiment A, a concentrate
should be such that when a coating solution contains about
0 5 to about 10 weight percent of the concentrate, the amounts
o ingredients present in the coating solution are: ~A)
at least about 0.5 x 10 mole /liter of zirconium and/or
hafnium; (B) at least about 0.025 x 10 3 mole /liter of
polyhydroxy compound, and (C) fluoride in an amount at least
sufficient to combine with substantially all of the zirconium
or hafnium to form a complex therewith, and the pH of the
coating solution is within the range of about 3 to about 5.
More preferably, the concentrate is such that when the coating
solution comprises about 0.5 to about 10 weight percent of
the concentrate, the coating solution comprises: (A) about
0.5 x 10 3 moles/liter to about 1.75 x 10 3 moles/liter of
zirconium, added as a fluozirconate such as sodium or potassium
--19--
1~74945
fluozirconate, most preferably ammonium fluozirconate; (B)
about 0.3 x 10 3 mole /liter to about 1.75 x 10 (~ole /liter
A of polyhydroxy compound added as gluconic acid; ~t about
0.5 x 10 3)mole /liter to about 2.50 x 1.0 3 mole /liter of
HF; and ~e~ nitric acid in an amount such that the pH of the
coating solution is within the range of about 3.4 to about 4.
.
By way of further example, with regard to. preferred
embodiment B, the concentrate should be such that when a
coating solution comprises about 0.5 to about 10 wei~ht
percent of the concentrate, the amounts of ingredients present
in the coating solution are: (A) at least about 0.5 x 10 3 m/l
of one or more of zirconium, titanium, and ha.fnium; and (B)
fluoride in an amount at least sufficient to combine with
~ubstantially all of the Zr, Ti, or Hf to form a complex
~ . . . -~ .
therewith, and (C) at least about 10 ppm of surfactant.
In a continuous coating operation, fluoride and the metal
are consumed and tt~se ingredients as well as others are
additionally depleted a9 a result of drag-out of the.solution
on the aluminum surface. The rate of depletion is related
to the shape of the surface being coated as well as the means
of application of the coating solution to the surface. In
addition to this depletion, there is a build-up in
concentration of dissolved aluminum as noted above. Therefore,
in a continuous coating operation, the ingredients should be
replenished.
-20-
- -
11~ 5
Replenishment may be effected by monitoring each ingre-
dient and adding an additional amount thereof as it is depleted
but preferably replenishment is accomplished by adding an
aqueous concentrate containing the ingredients to be replenished
in amounts effective to maintain said ingredients in the solution
in effective operating amounts. The replenishing composition
preferably contains a relatively high proportion of fluoride
when aluminum build-up is experienced in the coating solution.
Preferred sources of available fluoride for use in replenishing
are HF or ammonium bifluoride or a mixture thereof or HBF4.
Thus by way of example and with reference to preferred
embodiment A, the following is a recommended aqueous concentrate
for replenishing the coating solution of preferred embodiment A.
~A) about 31 x 10 3 mole/liter to about 251 x 10 3
mole/liter of zirconium and/or hafnium;
(B) about 19 x 10 3 mole/liter to about 148 x 10 3
mole/liter of the polyhydroxy compound; and
(C) a material which is a source of about 90 x 10 3
mole/liter to about 695 x 10 3 mole/liter of available
fluoride, preferably HF or ammonium bifluoride or a mixture
thereof.
By way of further example and with reference to preferred
embodiment B, the following is a recommended aqueous concentrate
for repleni5hing the coating solution of preferred embodiment B.
(A) about 0.05 mole/liter to about O.S mole/liter of
zirconium, titanium and/or hafnium;
(B) about 0.2 mole/liter to about 10 moles/liter of
fluoride; and
(C) about 1 to about 100 g/l of surfactant.
-21-
74945
The coating solutions of the present invention should
be applied to a clean aluminum surface. Available cleaning
compositions such as alkaline or acid cleaning sol~ltions can
be used to clean the aluminum surface according to conventional
techniques.
When coating drawn and ironed aluminum cans it is preferred
to subject the cans to a cleaning solution comprising an acidic
aqueous solution of a mixture of HF, H2SO4 and surfactant,
for example, solutions such as those described in U.S. Patent
Nos. 4,009,115; 4,116,853; and 4,124,407, each assigned to the
same assignee as the present invention, and the disclosures of
which are incorporated herein by reference.
.
The coating solution can be applied to the alumin~m
surface by any suitable method. For example, the solution
can be applied by spraying the aluminum surface, or the
aluminum surface can be immersed in the solution, or it can be
applied by roll or flow coating techniques or misting techniques.
The solution can be used to coat individual articles such as,
for example, cans, or it can be used to coat forms of
aluminum, such as aluminum strip, which are subsequently
fabricated into articles.
,
The temperature of the coating solution should be such
that the reactive ingredients of the solution bond to the
aluminum surface. For example, with a solution such as
-22-
1~7~345
preferred embodiment A, a temperature of at least about 110F
is generally required to produce the desired degree of corrosion
resistance and preferably such coating solution should have a
temperature of about 130F to about 150F. With a solution
such as preferred embodiment B, a temperature of at least
about 90F is generally required to produce the desired degree
of corrosion resistance and temperatures of up to about 140F
can be used, preferably about 110F to about 130F.
If the temperature of the coating solution is too high,
problems such as a dull and frosty appearing surface may be
encountered. The temperature at which this occurs depends on
various of the parameters of the coating operation, including~
for example, the time of contact of the solution with the
aluminum surface and the reactivity of the solution which
., .
depends on pH and concentration of ingredients in the solution.
By way of further example, with solutions such as preferred
embodiment A, precipitation of zirconium and/or hafnium
oxides.at temperatures in excess of about 160F may become
a problem if the p~ of the coating solution rises above about 4.5.
Desired coatings can be formed by contacting the coating
solution and the aluminum surface for at least about 5 seconds,
preferably at least about 15 seconds. The lower the temperature
o the coating solution, the longer should be the contact time,
and the higher the temperature of the solution, the shorter
-23-
1174~45
the contact time required. In general, it will be unnecessary
to contact the surface with the coating solution for more than
one minute
After the coating solution has been applied to the
aluminum surface, it should be water rinsed, including a
final deionized water rinse. Rinsing with water that contains
a small amount of dissolved solids may lead to a coating wh~ich
does not adhere well to a subsequently applied siccative
coating. In utilizing the present invention, it is not necessary
to rinse the coated surface with an aqueous solution of
chromium such as, for example, a hexavalent chromium solution.
After the coated surface has been water rinsed, or
otherwise treated as described above, the coating should be
dried. This can be done by any practical means, such as,
for example, oven drying or forced circulation of hot air.
Other available drying methods can be used.
After the coating has been applied, it can be subjected
to sanitary or decorative coating operations which include,
for example, applying to the coated surface siccative coatings.
These coatings are usually applied after the aluminum surface
has been coated, water-rinsed, and dried. In some applications
the sanitary c~ating is applied after the water rinse and both
the coating of the present invention and the sanitary coating
are dried simultaneously.
-24-
945
Siccative coatings which comprise the functional and/or
aesthetic coatings which overlie the coatings formed from the
coating solution of the present invention are well known, of
course, and can be formed from either water-based or organic
solvent-based compositions.
By way of example, it is noted that in an application
where aluminum cans are to be filled with beer, the cans
are treated with the coating solution of the present invention
and then sanitary and/or decora~ive coatings are applied.
Thereafter, the cans are filled with beer and sealed; after
which the beer-filled cans are subjected to pasteurization.
It is believed that the zirconium, titanium, or hafnium
present in the coating solution of the presént invention is
.. . . ..
present in a complexed form which is both soluble in the
solution and reactive with the aluminum surface to form thereon
a coating containing such metal without affecting the bright
shiny appearance of the aluminum surface. Accordingly, the
solution should be free of constituents which combine with
the aforementioned metals to form compounds and/or complexes
which precipitate from the solution and/or compounds or com-
plexes which are not reactive with the aluminum surface or
which are reactive, but in a mannér such that the bright shiny
appearance of the aluminum surface is altered.
-25-
4945
EX~PLES
The following examples present illustrati~e but non-
limiting embodiments of the present invention. Comparative
examples are also set forth.
Unless stated otherwise, the aluminum surfaces treated
with the solutions identified in the examples were drawn and
ironed aluminum cans which were first degreased, a~ necessary,
in an acidic aqueous cleaner containing sulfuric acid, hydro-
fluoric acid and detergent. Unless stated otherwise, the
coating solutions were applied by spraying for about 20 seconds
at the temperatures set ~orth below. After treatment with the
solutions identified in the examples, the aluminum surfaces
were rinséd with tap water and then with deionizea water, and
thereafter dried in an oven for 3.5 minutes at about 400F.
.
Thereafter, the aluminum cans were tested for corrosion
resistance by subjecting them to a water stain resistance
test simulating can exposure during commercial pasteurization
processes. The test consisted of immersing the cans for a
period of 30 minutes in a hot solution of distilled or
deionized water containing 0.22 g/l of sodium bicarbonate,
0.082 g/1 of sodium chloride, and 2.18 g/l of a water con-
ditioner ~Dubois 915, a proprietary product, supplied by Dubois
Chemical Inc., which exhibits a total alkalinity of 5.8% Na2O
and on analysis contains NaNO3, carbonate, triethanolamine and
-26-
1174945
dodecylphenyl polyethylene glycol). The solution was maintained
at 150- 5F during the test. After immersion, the cans were
rinsed with tap water, dried wlth a paper towel and then examined
~or staining. A cleaned-only aluminum surface, when subjected
to this test, turns black or brown after a few minutes. It
will be seen from examples set forth below that prior treat-
ment of aluminum surfaces with coating solutions of the present
invention can result in the provision of coated surfaces
which are not blackened or otherwise discolored or which xesist
blackening or other discoloration. The aluminum surfaces
were rated as follows: 5, perfect - identical to a treatea
but untested suxface; 4.5 - very slight diminishing of the
bright appearance of the suxface; 4.0 - very slight discoloration;
3.5 - light discoloration, but commercially acceptable; 3.0 -
discoloration that is considered not commexcially acceptable;
" ..~
0 - total failure, characterized by severe blackening.
In some of the examples the aluminum cans, aftex txeatment
with the indicated solutions, were also tested for paint
adhesion. After the treated surface was dried, as described
above, a portion of the surface was painted with a waterborne
white base coat (No. CE3179-2 white polyester sold by PPG
Industries Inc.) and the other portion of the surface was
painted with a waterborne overvarnish (Purair* S145-121 sold
by Inmont Corp.). After tne paint was cured, the painted
surface was immersed in boiling water for 15 minutes. After
removing the painted surface from the solution, it was cross
.
* "Purair" is a registered trademark
-27-
li7'~9~5
hatched, using a sharp metal object to expose lines of aluminum
which showed through the paint or lacquer, and tested for paint
adhesion. This test included applying Scotch** transparent
tape No. 610 firmly over the cross hatched area and then
drawing the tape back against itself with a rapid pulling
motion such that the tape was pulled away from the cross hatched
area. The results of the test were rated as follows: 10,
perfect, when the tape did not peel any paint ~rom th~ surface;
8, acceptable; and 0, total failure.
Examples 1-15, and
Comparative Examples Cl-C3
The following acidic aqueous concentr~te wasprepared for
use in connection with the first group of examples.
g~
fluozirconic acid (100~) 10.5
aqueous ammonia (29 wt. %) 5.9
nitric acid (70 wt. ~) 9
deionized water to make 1 liter
The above composition was prepared by combining an aqueous
solution of 23.4 grams of 45 wt. % fluozirconic acid with a
portion of the water, and thereafter the aqueous ammonia was
added to the resulting solution. A white precipitate was
formed, but it dissolved upon addition of nitric acid.
** "Scotch" is a registered trademark of the 3M Co.
-28-
.. . . ..
117~9~5
The resulting clear solution was diluted to 1 liter with
deionized water resulting in a concentrate that was used to
prepare treatment solutions at 2.5~ by volume in water comprising
2 parts deionized water and 1 part hard water. ~In the
examples, the term "hard water" refers to tap water rom
Ambler, Pennsylvania, which inclu~es about 80 to about lOb ppm
of calcium and has a conductivity o about 400 to about 600 mhos.)
To this soluti~n, there was added, in the amounts indicated in
Table 1 below, a nonionic surfactant sold under the trademark
Surfonic LF-17 by Jefferson Chemical Co., Inc. and which is
reported to be a low-foaming alkyl polyethoxylated ether.
Solutions of varying acidity were prepared by adjusting the
pH of the aforementioned base composition with appropriate
amounts of an aqueous solution of 15~ (w/v) ammonium
carbonate or dilute nitric acid.
.. .
The water-stain resistance of aluminum cans coated
with the compositions is reported in Table 1 below.
-29-
~i'7~9~
T~ble I
Cbnc. of p~l 3'esiS~rce
E:c. No.Sur~., F~ of ~nq Solu~
~1 5 3.5 3.3
S 3.~ 3.6
2 10 3.5 3.6
3 20 3.5 4.1
? 40 3.5
S 80 3.5 4.2
C-2 o 4 3.7
6 5 4 4.4
7 10 4 4,7
8 20 ~ ~1.5
9 40 4 4.5
- 10 80 4 4.6
C-3 0 4.5 ~.
~1 5 4.5 4.4
12 10 4.5 4.7
. 13 20 1.S 4.8
14 40 4.5 . 4.7
~S 80 4.5 ~.
The improvements in corrosion resistance achieved over the
pH range of 3.5 to 4.5 for the compositions evaluated in Table I
are clearly shown. Other tests show that for the particular type
of composition evaluated in Table 1, the water-stain resistance
of coatings formed from compositions with and without surfactant
were about the same when the pH of the composition was about 2.5.
Still other tests showed that for the particular type of composition
evaluated in Table I, but prepared from deionized water only and
containing 20 ppm of surfactant, improvements in water-stain
resistance were achieved when the pH of the composition was in
excess of 3.5, with substantial improvements being achieved at
a pH of about 4.
-30-
11'749~5
Examples 16-39, and
Comparative Examples C4-C6
.
The next group o examples shows the use of compositions
of the type described in Examples 1-15 and Comparative Examples
Cl-C3 but including also 0.1 g/l of gluconic acid which is
effective in improving the water-stain resistance of the coated
surface. Compositions of varying acidity and containing either
the surfactant used in the compositions of the first group of
examples or another surfactant were evaluated. Said other
surfactant was a modified polyethoxylated straight chain
alcohol which is considered to be a low-foaming material and
which is sold under the trademark Triton DF-16 by Rohm and
Haas Company. The specific compositions evaluated and the
results of the testing are set forth in Table II below.
't: _
Example ~0
Table III below shows the effect of gluconic acid
concentration on water stain resistance of coatings applied at
varying temperatures from 90F to 150F. Zirconium was
present in each solution in the form of ammonium fluozirconate
~(NH4)2ZrF6) at a concentration of 1.25 x 10 3 m/l,
and each solution was adjusted to a pH of 3.8 by the addition
of concentrated nitric acid. Two cans were employed in
determining the water stain resistance rating of each solution.
-31-
o e I
~ _ ¦ DDO~DOD.DD_-O_~_O__~O~ _~_~D___O~N~O_~D_N~DDDN
I ............................................................
~ O _ _D ~_~N~ ~ ~
c ~ a
_ o
e _ o DDOOOODODODDDDDDDDDDDDDODDOODDDDDODDODDDDDDDDDDDDDDDDDDDDDD
I _ _ _ _, _ _ _~ _ _ _ _ _ _ _ _ _ _ _ _ _ ~ O~ ", ~ _ O~ _ _ ~ O~ _ _ _ D~ _ _, U~ ~ _ ~ _, O~ _ ~ U~ C~ _ ~ ~ O~
C C
C- ~
~ L ~
O O
C _ I
I
_ N O DDDDDDDD~___~NN~ ~DDDD~N~N~DDDDDDDD
O~ ~ ¦ ODODDDDDDDODDDDDDDODOOOOODDDOOOODODO___________~__~NNN~
-C, _ I
_ D
L~ O
L~_ _~D-N~-~O~N~N~,__,.~.~ _~
1~ ~
~C
O C~ O C~ ~ O O ~ ~ O ~ C~ ~ ~ ~ ~ ~ ~ ~ ~ C~ ~ N
n~
~7 U~ o o O O O O O O O
D.~
~1
D.
a o o o o O O O O O O O O O O O O o o o o o o o O O o o
O L ~ U~ O O _~ 1/1 O O _1 It~ 0 0 _1 Ul O O --I Itl O O
I r~ o ~ o t~ o ~o '.D ~O 1~ O ~O ~O
b.~ ~ h.~ ~L b. h. ~ L~Lb. b. ~ b. b.~L
~O ~ ~ C~ O ~ N ~ I ~ N~N N~ N N ~ ~ I N ~ 3 ~O
-32-
~lL1'745~'~5
Example 41
Table IV below also shows the effect of gluconic acid con-
centration on water stain resistance, as well as on the adhesion
of water-borne siccative coatings, at two different pH and
temperature levels. Once again, zirconium was present in each
solution in the form of ammonium fluozirconate ~NH4)2ZrF6) at
a concentration of 1.25 x 10 3 mole/liter, and the pH of each
solution was adjusted by the addition of concentrated nitric
acid. Two cans were employed in determing each paint adhesion
rating ("Adhesion") while each watex stain resistance rating
("Resistance") represents the average rating of six cans.
TABLE IY
~rr-ot or Cluoonlo Aold Conoontrotlon on Hotor Stoln RoolJt~noo und Adhoolon Or ~utorborno Slooutlvo
Co-tln6o t 1,25 x 10 3M ~NH4)2Zr~6Conoontrutlon
_ _ _ _
Oluoonlo Aol~ Adhoolon
8-~Dl- No. Cono. ~ x 10 3)~HromD. ~P) Roolotonou CL3179-2 S145-121
1 0 3.5 125 110, 10 10, 7
2 0 3.5 135 2-2/310, 10 10, 8
3 0 4.25 125 410, 10 10, 10
4 0 4.25 135 2-2/310, 8 10, 8
0.5 3.5 125 510, 10 10, 10
6 0.5 3.5 135 510, 10 10, 10
7 0.5 4.25 125 4-2~310, 10 10, 10
ô 0.5 4.25 135 4-2/310, 9 10, 10
9 1.25 3.2 125 4-1/610, 10 10, 10
1.25 3.5 135 510, 10 10, 10
11 1.254.25 125 510, 10 10, 10
12 1.254.25 135 510, 10 10, 10
13 2.5 3.5 125 1-1/610, 10 10, 10
14 2.5 3.5 135 2-2/310, 8 10, 10
2.5 4.25 125 1-2/310, 10 lo, 10
16 2.5 ~.25 135 4-2/39, 9 10, 10
Examples 42-45
An aqueous concentrate of the tupe used to formulate the
compositions of Examples 1-15 was diluted with a sufficient
amount of water (two parts deionized water and one part hard
-33-
`Sd,~
i'i-
~1'7'~4S
water ~to yield) a coating solution containing 2.5% by volumeof the concentrate, to which was added 20 ppm of Surfonic LF-17.
Four solutions were thus prepared, to each of which was added
0.1 g/l of one of the following ingredients: glutaric acid,
asorbic acid, maleic acid or salicylic acid. The pH of each
of the compositions was 3.5 and each was used in treating
aluminum cans in the manner described above in connection with
the preceding examples. For all of the cans treated in this
way, water stain resistant ratings were above 3.5 and improved
adhesion was exhibited when the cans were painted with either
PPG CE 3179-2 or Inmont S145-121, water-based coating compo-
sitions, or with Clements P1099-7A or Clements P550-G, organic
solvent based coating compositions.
Examples 46-49
Other compositions were formulated by including 0.5 x 10 3
m/1 gluconic acid in each of the compositions of Examples
42-45 above. Coatings formed from such compositions exhibited
improved adhesion with respect to top coats formed from various
water-based resin coating compositions.
Example 50
Table V below shows the effect of ammonium fluozirconate
concentration on water stain resistance of coatings applied at
varying temperatures from 90F to 150F. Gluconic acid was
present in each solution at a concentration of 0.5 x 10 3 mole/
liter, and each solution was adjusted to a pH of 3.8 by the
addition of concentrated nitric acid. Two cans were employed in
determining the water stain resistance rating of each solution.
-34-
1 ~'J~ 345
TA~LE V
Erfect Or (NH4)2ZrF6 Conoentratlon on Water Staln Reslstance
at 0.5 x 10-3M Gluconlc Acld Concentratlon and pH of 3.8
~ater Staln
Sample No. (NH4)2zrF6cono. Temp. (~F) ~eslstanoe
0 90 o, O
2 0 110 0, 0
3 0 130 o, 0
4 o 150 0
0.1go o o
6 0.1110 0, 0
7 0.1130 0, 0
8 0.1150 0, 0
9 0.2590 -
0.25110 0, o
11 0.25130 3, 3
12 0.25150 3, 3
13 0.5090 0, 0
14 0.50110 2 2
0.50130 3 3
16 0.50150 4, 4
17 0.7590 2, 2
18 0.75110 2, 2
19 0.75130 3, 3
0.75150 4, 4
21 1.2590
22 1.25110 2, 2
23 1.25130 3, 3
24 1.25150 4, 4
1.7590 1, 1
26 1.75110 2 2
27 1.75130 4 4
28 1.75150 5, 5
29 2.2590 1, 1
2.25110 2, 2
~1 2.25130 4, 4
32 2.25150 5, 5
33 5 0 9 2, 2
34 5.0110 2, 2
5.0130 4, 4
36 5.0150 4, 4
Example 51
Table V~ below shows the effect of ammonium fluozirconate
concentration on water stain resistance, as well as on the
adhesion of waterborne siccative coatings, at three different
pH and two different temperature levels. Again, gluconic acid
was present in each solution at a concentration of 0.5 x 10 3
mole/liter, and the pH of each solution was adjusted by the
addition of concentrated nitric acid. Two cans were employed in
determining each paint adhesion rating while each water stain
resistance rating represents the average of six cans.
-35- -
T~aLE VI
Erroot o~ (NH4)2ZrF6 Conoontrotlon on ~ater Stoln Ro~lat~no~ and Adhoalon Or ~at~rborno Sloo~tlv~
Co-t~ng~ at 0.5 1 10 3~ Gluoonlo Aoid Conoontratlon
(NN )2ZrF ~at~r St~ln Adb~ion
~ample No. ~ono. (M ~6 lo~3) PH Temv. ~F)~oalatano~ CE3179-2 S145-121
1 0.75 3.5 125 4-2~310, 8 10, 10
2 0.75 3.5 135 5 10, 10 10, 10
3 0.75 4.o 125 4-s~6 9, 9 lo, lo
4 0.75 4.0 135 4-2/3 10 8 10, 10
0.754.25 125 4 lo 1~ 10 o
6 0.754.25 135 4 10, ô 9 9
7 1.25 3.5 125 5 10 10 10, lo
8 1.25 3.5 135 5 10 10 lo lo
9 1.25 4.0 125 5 10, 10 10 10
1.25 4.0 135 5 10, 8 l~o 9
11 1.254.25 125 4-2/3 10, 10 10 10
12 1.254.25 135 4-1~3 10 9 10 10
13 1.75 3.5 125 4 lo 10 10 8
14 1.75 3.5 135 4 lo, 8 9, 9
1,75 4.0 125 4 10, lo 10 10
16 1.75 4.0 135 4 10, 10 10 10
17 1.754.25 125 4 10 10 10 10
18 1.754.25 135 4 10 10 10 10
19 - - - - - - - Cl~an~d Only - - - - - - - - - - - - - - O 10, 9 10, 10
Example 52
Table VII below illustrates the water stain resistance of
coatings formed from a solution of hafnium tetrafluoride,
~ydrofluoric acid and gluconic acid at varying temperatures from
90F to 150F. The solution contained 1.25 x 10 mole/liter
of hafnium tetrafluoride, 2.5 x 10 mole/liter of gluconic
acid. For comparative purposes, coatings were also formed from
a like solution free of gluconic acid. The pH of both solutions
were adjusted to 3.8 by the addition of concentrated nitric
acid. Two cans were employed in determining the water stain
resistance rating of the solutions.
-36-
1~4~3~S
TA~LE VII
~at~r St~ln Re~lstano~ ot C~atlngs Form~d Fro~ A Sol~tlon or
N~rnlum T~trorluorlde, ~ydro~luorlc Acld ~nd Gluoonlo Aold
~rF4 HF Gluoonlc Acld ~t~r ~t~ln
sa~Dlo No. ~M ~ 1~ 3~ M ~ 10 3) pN Te~ ~ F) Ro~latnnco_
1 1.25 2.5 0 3.~90 0
2 1.25 2.5 0 3.~110
3 -1.25 2.5 0 3.ô130
4 1.25 2.5 0 3. B 150 2
1.25 2.5 0.5 3.890
6 1.25 2.5 0 5 3.8110
7 1.25 2.5 0.5 3.8130 5
8 1.25 2.5 ~.5 3.8150 5
Examples 53-56
Tables VIII, IX and X illustrate the effect of pH and
temperature on the water stain resistance of coatings formed
from a solution of ammonium fluozirconate and gluconic acid, as
well as on the adhesion of water-borne siccative coatings to
such coatings. The solution employed contained 1.25 x 10 3
mole/liter of the ammonium fluozirconate and 0.5 x 10 3 mole/
liter of the gluconic acid. For comparative purposes, coatings
were also formed from a like solution free of gluconic acid.
The pH of both solutions was adjusted to the values shown in
the tables by the addition of concentrated nitric acid. Such
solutions were then applied at varying temperatures from 90F
to 160F. Two cans were employed in determining each water
stain resistance rating and one can was employed in determining
each paint adhesion rating at each pH and temperature value.
The condition of each solution (clear or cloudy) at each pH and
temperature level employed is also set forth. As can be seen
from Tables X and XI, the presence of gluconic acid is important
at pH 4.5 and 5.0 in maintaining a clear solution and preventing
pr~cipitation.
-37-
~ L~
TALLE YIII
er~ot Or Somperaturo on ~ater Staln Rosi~tanoe Or Coatlng~ Formod From a Solution Or
1.25 ~ 10 3N (NN4)2ZrF6 and 0.5 ~ 10 3H Cluoonlo Aold at a pH Or 3.0, ~nd on the Adhe~ion
or ~atorborno Sloo~tlve Coatln~a to Suoh Coatln~s
Gluoonlo Aold ~ater StalnAdhe~lon Solu~lon
Sample_No. Cono. (M x 10 3) SeQD. (P) ~e~l~tanco Ce3179-2 Condltlon
1 090 2,2lrJ Clear
2 D100 2,210 Clear
3 0110 1,110 Cloar
4 0120 1,110 Cl~ar
0130 1,110 Clear
6 0140 2 210 Clear
7 0150 3 310 Clear
8 0160 3,310 Cle~r
9 0-590 3,310 Cle~r
o.5 100 3~3 10 Clear
11 0.5 110 3~3 10 Clear
12 0.5 120 4 4 10 Cl~ar
13 0.5 130 4 4 10 Clear
14 0.5 140 5,5 10 Ciear
0.5 150 5,5 __ Cloar
16 0.5 160 5,5 7 (hoavy Cloar
palnt)
~ TAOLE IX
Erroot Or S--poraturr on ~ator Staln ~o~l~tanoe or Coatln6~ Formod From a Solutlon Or
1.25 % 10 3M (NH4)2ZrP6 and 0.5 ~ 10 3M Gluoonlo Aold at a pH Or 3.5, and on the Adbe~lon
Or ~atorborno Slooatlve CoatlnEs to Suoh Co~tln~
aluoonlo Aold ~ater StalnAdhoslon Solutlon
samDlo Uo.Cono. (M x 10 3) Tomp. (~F~Posl~tanoo CE3179-2 Condltlon
1 090 0,0 10 Cl~ar
2 0100 0 0 10 ClAar
3 0110 0 0 10 Cloar
4 0120 0,0 10 Clear
0130 1 1 10 Cloar
6 0140 2 3 10 Cloar
7 0150 2,3 10 Clear
8 0160 2 3 10 Cloar
9 0.5 90 2 2 10 Clear
0.5 100 2,2 10 Cloar
11 0.5 110 3,3 10 Clear
12 0.5 120 3,4 10 Cloar
13 0.5 130 ll~4 10 Cloar
14 0.5 140 5,5 10 Clear
0.5 150 5 5 10 Ciear
16 0.5 160 5 5 10 Cloar
--38--
~1 7 .~ ~3 4 5
ShSLE X
Erroot Or Somporaturo on Wator Staln R~al~tanoo Or Co~tln~ Por~od Fro~ a Solutlon Or 1 25
~ 10 3N (NH4)2ZrF6 and 0 5 ~ 10 3M Oluconlo Aold at a pN or 4 5, and ln tho Adboolon Or
Watorborno Slooatl~e Coatlng~ to Suoh Coatln~
aluoonlo Aoid 3 ~ater StalnAdhoolon 901utlon
9a~plo No Cono ~N ~ 10 ) TOrD. 1 F~ Roolatanoe CE3179-2 Condltlon
1 0 90 0,0 10 Cloar
2 0 100 0,0 10 Sll~ht Naz~
3 0 110 0,0 10 Falnt Nazo
4 0 120 3,1 10 Cloudy
0 130 2,1 10 Cloudy
6 0 140 2,2 10 Cloudy
7 0 150 2,2 10 Cloudy
ô 0 160 2,3 10 ~ory Cloudy
9 0 5 90 0,0 10 Cloar
0 5 100 0,1 10 Cloar
11 0 5 110 2,1 10 Cloar
12 0 5 120 3,1 10 Cl~r
13 0 5 130 4 4 10 Cl~ar
14 0 5 140 4,4 10 Cloar
0 5 150 4,4 10 Cloar
16 0 5 160 4,4 10 Cloar
SANLE XI
Ett-ot ot Souporaturo on W~tor Staln Roalatanoo Or Co~tlnza For~od Fron Solutlon or 1 25
10 3N (hN4)2ZrF6 and 0 5 ~ lD 3N Oluoonlo Aold at a pH Or 5 0, and on tho Adboalr,n Or
~-torborno 9100-tl~ Coatlnga to 9uoh Coatlnga
aluoonlo Aold Wator ~talnAdhoaloD Solutlon
SanDlo No Cono(N ~ 10 3)So~P ( F)RoJlatanoo CE3179-2 Condltlon
1 0 90 2,Z 10 Cloudy
2 0 100 2,2 10 Cloudy
3 0 110 3,3 10 Cloudy
4 0 120 4,3 10 Cloudy
0 130 4,3 10 Cloudy
6 0 160 4,3 10 Cloudy
7 0 5 90 3,2 10 Cloar
ô 0 5 100 3~3 10 Cloar
9 0 5 110 3,3 10 Clo-r
0 5 120 4,3 10 Cloar
11 0,5 130 4 3 10 Cloar
12 0 5 140 4 3 10 Clo-r
13 0 5 150 4,3 10 Cloar
14 0 5 160 4,2 10 Cloar lnltl-lly,
oloudy artor
otandln~ tor,Jl hr
--39--
'X
945
Exsmple 57
Table XII below shows how the addition of phosphate to an
ammonium fluozirconate solution adversely affects the adhesion
of water~orne siccative coatings to coatings formed from such
solutions. The concentration of phosphate and ammonium fluo-
zirconate in each of the solutions prepared is shown in the
table. The phosphate was added as phosphoric acid. The pH
of the solutions varied as shown in the table. Once again,
nitric acid was employed to adjust the pH. The solutions were
applied at a temperature of 130F. Two cans were employed in
determining each paint adhesion rating of each solution.
TA3LE YII
erroot Or Phosphato Conoontratlon On Adhoslon Or ~atorborn~
Sloaatlv~ Coatlng~ to Coatlnt~ Forood rron Fluozlroonate ~olutlona
(~4)2ZrF6 PhoJphato Adhoslon
S ~Dlo No.~M x 10 3) ~H x 10 3) DH CE179-2 S145-121
1 0.5 0 3.5 10, 9 9,6
2 0.5 0 4.0 10,10 8,7
3 0.5 0.1 3.5 10, 5 8,6
4 0.5 0.1 4.0 10, 5 7.0
0.5 0.25 3.5 O, 0 9,6
6 0.5 0.25 4.0 O, O ~,7
7 1.25 0 3.5 10,10 9,6
8 1.25 0 4.0 10, 9 8,7
9 1.25 0.1 3.5 7, 0 8,7
1.25 0.1 4.0 6, 5 10,0
11 1.25 0.25 3.5 O, 0 7,7
12 1.25 0.25 4.0 O, 0 8,0
13 2.5 0 3.5 10,10 10,8
14 2.5 0 4.5 10, 9 9,6
2.5 0.1 3.5 0, 0 10,9
16 2.5 0.1 4.0 9, 8 8,8
17 2.5 0.25 3.5 7, 5 8,5
18 2.5 0.25 4.0 O, 0 9,5
19- - - - - -Cloanod Only- - - - - - - - - - - - - - -10,10 10,8
-40-
," !
.l'~ ` .
s
Example 58
Table XIII below shows how the addition of phosphate and
gluconic acid to ammonium fluozirconate solutions affects the
adhesion of waterborne siccative coatings to coatings formed
from such solutions. The concentration of each of these
materials in each of the solutions prepared is shown in the
table. The phosphate was added as phosphoric acid. The pH
of the solutions was varied as shown in the table and concen-
trated nitric acid was employed to adjust the pH. The
solutions were applied at the temperatures indicated. Two cans
were employed in determining each paint adhesion rating of each
solution.
TABLE XIII
Erroot Or Phooph-to nnd Cluoonlo ~old Conoontratlon on Adhonlon Or ~atorborno Slooatlvo
Co-tlngo to Co-tlnga Yor-od rro- Fluozlroon~to Solutlono
~NH4)2zrF6 Phoophatc aluoonlo ~old ~h-~lon
90~Dlo No, ~H ~ 10 3) ~H x 10 3) ~H ~ 10 3) DH ~ L~l CE3179-2 S145-121
1 0.25 0 0 4.0 110 10,10 10, 8
2 0.25 0 0 4.0 130 10,10 8, 8
3 0.25 0.1 0 4.0 110 10, 8 10,10
4 0.25 0.1 0 4.0 130 7, 7 10 ô
0.25 0 0.5 4.0 110 10,10 10 10
6 O.Z5 0 0.5 4.0 130 10,10 10,10
7 0.25 0.1 0.5 4.0 110 ~ 6 10,10
8 0.25 0.1 0.5 4.0 130 0 0 10, 7
9 0.25 0 0 3.5 110 10 10 10 10
0.25 0 0 3.5 130 10 10 10 10
11 0.25 0.1 0 3.5 110 5, 5 10, 7
12 0,25 0.1 0 3.5 130 0 5 0, 0
13 0.25 0 0.5 3.5 llo lo lo lo,lo
14 0.25 0 0.5 3.5 130 10,10 lo,lo
0.25 0.1 0.5 3:5 110 10 7 7, 6
16 0.25 0.1 0.5 3.5 130 t 7 7, 7
17 1.25 0 0 3.5 110 10 10 10 7
la 1.25 0 0 3.5 130 10 10 9 7
1,25 0.1 0 3.5 110 10,10 10,10
1.25 0.1 0 3.5 130 0, 0 7, 5
21 1.25 0 0.5 3.5 110 10,10 10, 8
22 1.25 0 0.5 3.5 130 10, 8 10, 8
23 1.25 0.1 0.5 3.5 110 10 7 5 5
24 1.25 0.1 0.~ 3.5 130 10 8 7 0
25- - - - - -Cloanod Only- - - - - - - - - - - - - - - - - - - - - - - - - - 10,10 10,10
-41-
~r
~p.
Example 59 ~ 4S
In order to demonstrate that aluminum surfaces coated with
a coating solution containing gluconic acid, zirconium and
fluoride undergo the so-called "muffle test", while aluminum
surfaces coated with a like coating solution free of gluconic
acid do not, a number of aluminum cans were coated with
solutions having the compositions shown in Table XIV below.
The coated cans were then heated at a temperature of 900F for
5 minutes and the color of the cans was observed. The results
observed are set forth below in Table XIV. The solutions
employed each had a pH of 4.25, obtained by addition of con-
centrated nitric acid, and were supplied at the temperatures
shown in Table XIV.
TA~LE XIII
Huttlo Tont Ronultn or Cootod Alumlnuo Surraol~r
(NN4)2Zrr6 Oluoonlo Aald 8urr~loo Color At~or Ro~tlnB
Dl- NO, ~IS X 10 3) (1~X 10 3) _ TO~ID. ~F) t 900F rOr 5 ~lnut-o
1. 25 0 125 ~llvor
2 1.25 0 135 811v-r
3 1.25 O.S 125 llght goldon bro~ln
4 1.25 0.5 135 llght gold-r brolln
Cl-on-d Orly 811v-r
In summary, it can be said that the present invention
provides the means for forming on an aluminum surface a non-
chromate coating which is colorless and clear without modifying
the appearance of the aluminum surface. The coated surface
exhibits improved corrosion resistance, as exemplified by the
test results reported above, and exhibits excellent adhesion to
overlying siccative coatings formed from either water-based or
organic-solvent based coating compositions.
-42-
.;'
j
