Note: Descriptions are shown in the official language in which they were submitted.
CA 02242995 1998-07-14
WO 97l2700I PCT/US97/00012
a
PASSIVATION COMPOSITION AND PROCESS FOR COATING
Field of the Invention
This invention relates to compositions and processes for passivating, i.e.,
forming
a corrosion protective surface layer. on metal surfaces that consist
predominantly of
aluminum and/or zinc. A wide variety of such surfaces are in normal use,
including
s many kinds of galvanized and/or aluminized steel, and the invention is
applicable to such
surfaces which differ from the underlying metal, as well as to solid alloys of
aluminum
and/or zinc. In fact. the invention is particularly advantageous for use on a
surface of 55
aluminum, 43.5 % aluminum. and 1.5 % Si that is often itself used as a coating
on
underlying steel.
,o Statement of Related Art
Traditionally, most zinciferous and/or aluminiferous surfaces have been
passivat-
ed by chemical treatment with aqueous liquid compositions containing at least
some hex-
avalent chromium. However, the adverse environmental effects of hexavalent
chromium
that have come to public attention in recent years have resulted in
development of aitern-
,s ative, chromium-free compositions for this purpose. A combination of
molybdate and
phosphate has been recommended for this purpose by workers from the Centre for
Ad-
vanced Electroplating of the Technical University of Denmark. However, no
chromiu~m-
free passivating treatment previously known has been found to be suitable for
all com-
1
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WO 97/27001 PCT/US97/00012
mercial uses for which replacement of chromium-containi_:g treatments have
been de-
sired.
IaESC IPTION OF THE INVENTION
Gbiect of the Invention
Various alternative and/or concurrent objects of this invention are: (i) to
provide
an entirely or substantially chromium-free composition and process for
passivating that
will provide an adequate corrosion resistance in comparison with previously
used high
quality chromate containing passivating agents; {ii) to provide an economical
passivating
treatment; and (iii) to reduce pollution potential.
General Principles of Description
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
~s stated is generally preferred, however. Also, unless expressly stated to
the contrary: per-
cent, "parts of', and ratio values are by weight; the description of a group
or class of ma-
terials as suitable or preferred for a given purpose in connection with the
invention im-
plies that mixtures of any two or more of the members of the group or class
are equally
suitable or preferred; description of constituents in chemical terms refers to
the constitu-
zo ents at the time of addition to any combination specified in the
description, and does not
preclude chemical interactions among the constituents of a mixture once mixed;
specifi-
cation 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 spec-
ified should preferably be selected from among other constituents explicitly
specified in
2s ionic form, to the extent possible; otherwise such counterions may be
,freely selected,
except for avoiding counterions that act adversely to the objects of the
invention; the
terms "molecule" and "mole" and their grammatical variations may be applied to
ionic,
elemental, or any other type of chemical entities defined by the number of
atoms of each
type present therein, as well as to substances with well-defined neutral
molecules; the
so first definition of an acronym or other abbreviation applies to all
subsequent uses herein
of the same abbreviation and applies mutatis mutandis to normal grammatical
variations
of the initially defined abbreviation; the term "paint" includes all Iike
materials that may
2
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WO 97/27001 PCT/US97/00012
be designated by more specialized terms such as lacquer, enamel, varnish,
shellac,
topcoat, and the like; and the term "polymer" includes "oligomer",
"homopolymer", "co-
polymer", "terpolymer", and the like.
Summary of the Invention
It has been found that one or more of the objects stated above for the
invention
can be achieved by the use of a passivating aqueous liquid composition that
comprises,
preferably consists essentially of, or more preferably consists of, water and:
(A} dissolved phosphate anions;
(B) dissolved, stably dispersed, or both dissolved and stably dispersed
molybdenum-
containing anions, compounds, or both compounds and anions in which molyb-
denum has an oxidation state less than +6; and, optionally, one or more of the
fol-
lowing:
(C} a dissolved, stably dispersed, or both dissolved and stably dispersed
component
selected from the group consisting of reducing agents, non-molybdenum-can
15 taming products from reactions in which the reducing agents reduce other
materi
al, or both, said reducing agents and products from reactions thereof not
being
part of either of previously recited components (A) and (B);
(D) dissolved, stably dispersed, or both dissolved and stably dispersed
moIybdenum
containing anions, compounds, or both compounds and anions which are not part
zo of any of previously recited components (A) through (C) and in which
molybden
um has an oxidation state of +6;
(E) a dissolved component selected from the group consisting of simple and
complex
anions containing fluorine: atoms, said anions not being part of any of
previously
recited components (A} through (D);
z5 (F) a component of dissolved, stably dispersed, or both dissolved and
stably dis-
persed metal oxide or metal oxides that are not part of any of the previously
recit-
ed components (A) through (E); and
(G) a component of surfactant that is not part of any of the previously
recited com-
ponents (A) through (F).
ao The phrase "stably dispersed" when used herein to describe an insoluble
compon-
ent in a liquid continuous phase, as in the definitions of components (B),
(C), (D), and
(F) recited above, means that the insoluble component is not spontaneously
concentrated
3
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WO 97/27001 PCT/US97/OOOI2
into any separate liquid or solid phase perceptible with unaided human vision
as distinct
from, but in contact with, the liquid continuous phase within a period of
observation of
the combination of stably dispersed insoluble component and liquid continuous
phase for
hours, or preferably, with increasing preference in the order given, for I, 3,
5, 10, 30,
s 60, 90, I20, 240, or 360 days.
Various embodiments of the invention include working compositions for direct
use in treating metals, make-up concentrates from which such working
compositions can
be prepared by dilution with water, replenisher concentrates suitable for
maintaining op-
timum performance of working compositions according to the invention,
processes for
io treating metals with a composition according to the invention, and extended
processes
including additional steps that are conventional per se, such as cleaning,
rinsing, and sub-
sequent painting or some similar overcoating process that puts into place an
organic bind-
er-containing protective coating over the metal surface treated according to a
narrower
embodinnent of the invention. Articles of manufacture including surfaces
treated accord-
is ing to a process of the invention are also within the scope of the
invention.
Description of Preferred Embodiments
For a variety of reasons, it is sometimes preferred that compositions
according
to the invention as defined above should be substantially free from many
ingredients used
in compositions for similar purposes in the prior art. Specifically, when
maximum stor-
zo age stability of a concentrate, avoidance of possibly troublesome anions,
and/or minimi-
zation of pollution potential is desired, it is preferred, with increasing
preference in the
order given, independently for each preferably minimized component listed
below, that
these compositions contain no more than 25, 15, 9, 5, 3, I .0, 0.35, 0.I0,
0.08, 0.04, 0.02,
O.OI, O.OOI, or 0.0002, percent of each of the following constituents:
nitrite; halates and
zs perhalates (i.e., perchlorate, chlorate, iodate, etc.); hydroxyiamine and
salts and complex-
es of hydroxyIamine; chloride; bromide; iodide; organic compounds containing
vitro
groups; hexavalent chromium; ferricyanide; ferrocyanide; and pyrazole
compounds.
Components such as these may not be harmful in some instances, but they have
not been
found to be needed or advantageous in compositions according to this
invention, and
ao their minimization is therefore normally preferred at least for reasons of
economy. ,
The dissolved phosphate ions that constitute necessary component (A) may be ob
tained from a variety of sources as known in the art. Normally much of the
phosphate
4
CA 02242995 1998-07-14
WO 97/2700i PCT/US97/00012
ion content will be supplied by phosphoric acid added to the composition, and
the stoi-
chiometric equivalent as phosphate ions of all undissociated phosphoric acid
and all its
anionic ionization products in solution, along with the stoichiometric
equivalent as phos-
P
phate ions of any dihydrogen phosphate, monohydrogen phosphate, or completely
new
s traiized phosphate ions added to the composition in salt form, are to be
understood as
a
forming part of phosphate ions component (A), irrespective of the actual
degree of ioni-
zation and/or reaction to produce some other chemical species that exists in
the
composition. If any metaphosphoric acid, other condensed phosphoric acids, or
salts of
any of these acids are present in the compositions, their stoichiometric
equivalent: as
phosphate is also considered pa~.-t of component (A). Generally, however, it
is preferred,
at least partly for reasons of economy, to utilize orthophosphoric acid and
its salts as the
initial source for component (A). (The formation of complex phosphomolybdate
ions in
a final composition according to the invention is believed likely to occur,
but the precise
chemical nature and concentrations) of any such species formed are not known.)
In a working passivating aqueous liquid composition according to the
invention,
the concentration of phosphate ions and/or their stoichiometric equivalents as
noted
above preferably is at least, with increasing preference in the order given,
2.0, 3.0, 4.0,
5.0, 6.0, 7.0, 8.0, 9.0, I 0.0, 10.5, I I .0, 11.5, 12.0, or 12.2 grams per
liter (hereinafter usu-
ally abbreviated as "glL") of total composition and independently preferably
is not more
zo than, with increasing preference in the order given, 200, 100, 80, 70, 65,
60, 55, 50, 46,
43, 40, 30, 27, 24, 2I, 19, I7, 15, or 13 g/L.
The dissolved and/or dispersed substances) which contain molybdenum in a val-
ence state lower than +6 and constitute the second necessary component of a
working
passivating aqueous liquid composition according to the invention are
preferably, at least
zs in part for reasons of economy, provided by in situ reaction between
molybdenum triox-
ide (in which molybdenum has the +6 valence state) and a reducing agent in the
presence
of water and phosphate ions, preferably, in order to complete the reaction
within a rea-
sonable time, at a temperature well above normal ambient temperature. This
reaction
preferably is caused to occur in a mixture which comprises, more preferably
consists es-
ao sentially of, or still more preferably consists of, water, molybdenum
trioxide, orthophas-
a
phvric acid, and reducing agent and which is suitable for use, after this
reaction, as a
make-up concentrate composition according to the invention that, when diluted
with wat-
CA 02242995 1998-07-14
WO 97/27001 PCT/US97/00012
er only, supplies alI of components (A), (B), (C), and (D) as defined above
that are need-
ed in a working passivating aqueous liquid composition according to the
invention. In
such a concentrate make-up composition: (i) the amount of molybdenum trioxide
used
0
preferably is at least, with increasing preference in the order given, 20, 40,
60, 70, 80, 85,
s 90, 95, 100, 105, 108, I 11, or I I3 grams per kilogram of the total amount
of material t
mixed (hereinafter usually abbreviated as "glkg") and independently preferably
is not
more than, with increasing preference in the order given, 400, 350, 300, 250,
200, 175,
155, 140, 130, 125, 120, or 1 I5 g/kg; {ii) independently, the amount of
phosphate ions
used preferably is at least, with increasing preference in the order given,
20, 40, 60, 70,
,0 75, 80, 85, 90, 95, or 100 g/kg and independently preferably is not more
than, with in-
creasing preference in the order given, 700, 600, 550, 500, 475, 450, 445,
435, 430, 400,
350, 300, 250, 200, 150, or 125 g/kg; (iii) independently, the amount of
reducing agent
used preferably is at least, with increasing preference in the order given, 2,
4, 6, 8, 10,
12, 14, 16, 18, 30, 50, 70, or 90 g/kg and independently preferably is not
more than, with
,s increasing preference in the order given, 200, 175, 150, 125, or 100 g/kg;
(iv) all other
ingredients constitute the balance of the material mixed to form the
concentrate make-up
composition; and (v) independently, the ratio of the amount of molybdenum
trioxide to
the amount of phosphate ions mixed to prepare the concentrate make-up
composition is
at least 0.20:1.0, 0.30:1.0, 0.35:1.0, 0.45:1.0, 0.65:1.0, 0.75:1.0, 0.85:1.0,
0.95:1.0, or
2o I .05:1.0 and independently preferably is, with increasing preference in
the order given,
not more than 4.0:1.0, 3.5:1.0, 3.0:1.0, 2.5:1.0, 2.0:1.0, 1.5: i .0, I
.3:1.0, or 1.2: I Ø All
of these stated preferences also apply to concentrate make-up composition
prepared in
any other way, except that the stoichiometric equivalent as Mo03 of the total
molybdenum content of components (B) and (D) as described above is substituted
for the
zs amount of Mo03 specified in the preferences in this paragraph.
Only actual reducing agent is preferably mixed with other ingredients as noted
in the immediately preceding paragraph to prepare a passivating aqueous liquid
concen-
trate composition according to the invention, but one or more products from
the reduc-
tion effected by the reducing agent may of course remain in the composition.
The reduc-
so ing agent added initially preferably is selected from the group consisting
of organic com- ,
pounds in which the ratio of oxygen atoms to carbon atoms is at least, with
increasing
preference in the order given, 0.3:1.0, 0.6:1.0, 0.7:1.0, or 0.8:1.0 and
independently pref-
6
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WO 97/27001 PC~'/US97/00012
erably is not more than, with increasing preference in the order given,
1.5:1.0, 1.3:1.0,
or 1.1:1Ø Independently, primarily for reasons of economy, the reducing
agent is pref
erably selected from substances containing no atoms other than carbon, oxygen,
and hy-
drogen, and most preferably is starch. Whatever the reducing agent used, it
preferably
s is sufficiently effective as a reducing agent and is used in a sufficient
amount to react
with the preferred amounts of molybdenum trioxide as given above in the
presence of
water and the preferred amounts of phosphoric acid as given above to convert
the entire
amount of molybdenum trioxide used into one or more soluble and/or stably
dispersed
molybdenum-containing substances, in which at least part of the molybdenum is
in a vaI-
,o ence state lower than +6.
The amount of molybdenum that is in a valence state lower than +6 in a composi-
tion according to the invention may be and preferably is measured by titration
of a samp-
le of the composition with potassium permanganate solution to a color change
from blue
or green to yellow, orange, or brown. This method indicates that not nearly
all of the
,s total dissolved and/or stabiy dispersed molybdenum atoms in most preferred
concentrate
make-up compositions according to the invention are in a lower valence state.
( A conse-
quence of this fact is that the presence of optional component (D) in a
passivating aque-
ous liquid composition according to the invention is normally preferred.)
Inasmuch as
the actual valence state or states lower than +6 in which molybdenum atoms
exist in
2o compositions according to the invention are not known, for convenience in
calculation
it is assumed that all such atoms are in the +5 valence state. Based on this
assumption
and a measurement by titration as described above, it has been found to be
preferred,
based primarily on the degree of corrosion protection achieved, for the
fraction of dis-
solved andlor stably dispersed molybdenum atoms in a composition according to
the in-
2s vention that are in a valence state lower than +6 to be at least, with
increasing preference
in the order given, 1.0, 2.0, 3.0, 4~.0, 5.0, 6.0, 7.0, 7.5, 8.0, 8.5, 9.0,
9.3, or 9.5 % and in-
dependently preferably to be not more than, with increasing preference in the
order giv-
en, 30, 25, 20, I5, or 10 %.
It is also normally preferred that at least one of optional components (E) and
(F)
so should be present in at least working compositions according to the
invention, because
the presence of at least one of these components normally increases the
corrosion protec-
tion and/or the resistance to discoloration of the passivated surface formed.
Normally
7
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WO 97/27001 PCTJLTS97/00012
fluoride-containing component (E) is more preferred than component (F),
particularly
when selected from the group consisting of fluozirconic acid, fluotitanic
acid, fluosilicic
acid, fluoboric acid, and the salts of all these acids. Fluozirconic acid and
its salts are
most preferred. In a working passivating aqueous liquid composition according
to the
s invention, the total concentration of fluorine atoms in anions in component
(E) preferably
is at least, with increasing preference in the order given, 0.02, 0.04, 0.06,
0.08, 0.10,
0.1 S, 0.20, 0.22, or 0.24 g/h and independently preferably is, primarily for
reasons of
economy, not more than, with increasing preference in the order given, 2.0,
1.5, 1.0, 0.80,
0.70, 0.60, 0.50, 0.45, 0.40, 0.35, 0.30, 0.28, or 0.26 g/L.
,o If component (F) is present in a working or a concentrate passivating
aqueous li-
quid composition according to the invention, it is preferably selected from
silica and/or
aIumina in colloidally dispersed form.
Surfactant component (G) is not normally needed, but in some cases may be ad-
vantageous to promote thorough and uniform wetting of the surface to be
passivated.
~s A working passivating aqueous liquid composition according to the invention
preferably has a pH value that is not more than, with increasing preference in
the order
given, S, 3, 2.5, 2.2, 1.9, or 1.7 and independently preferably is at least,
with increasing
preference in the order given, -1.0, -0.5, 0.0, 0.5, 0.70, 0.80. 0.85, 0.90,
0.95, or I.O.
A process according to the invention in its simplest form consists of bringing
a
2o metal surface to be passivated into physical contact with a working
composition accord
ing to the invention as described above for a period of time, then
discontinuing such con
tact and drying the surface previously contacted. Physical contact and
subsequent sepa-
ration can be accomplished by any of the methods well known in the metal
treatment art,
such as immersion for a certain time, then discontinuing immersion and
removing adher-
zs ent liquid by drainage under the influence of natural gravity or with a
squeegee or similar
device; spraying to establish the contact, then discontinuing the spraying and
removing
excess liquid as when contact is by immersion; roll coating of the amount of
liquid
followed by drying into place, and the like.
Preferably the temperature of the working passivating aqueous liquid
composition
so during a passivation process according to the invention is at least, with
increasing prefer- ,
ence in the order given, 15, 20, 25, 30, 34 or 37 °C and independently
preferably, primar-
ily for reasons of economy, is not more than 66, 60, 55, or 50 °C. The
quality of the pas-
8
CA 02242995 1998-07-14
WO 97/27001 PCT/IJS97/00012
sivation layer formed is not known to be substantially affected by the
temperature doting
passivating if the temperature is within any of these preferred limis; the
primary reason
for the preference for a minimum temperature during passivating that is
greater than the
normal ambient temperature is that with such a passivating temperature and
squeegeeing
s off of any adherent liquid promptly after discontinuing contact of the
surface to be
t
gassivated with a working passivating aqueous liquid composition according to
the
invention, the surface will dry spontaneously in ambient air within a few
seconds to form
a passivated surface according to the invention. This method of operation is
particularly
well adapted to most existing coil processing plants.
The time during which physical contact is maintained between the metal surface
to be passivated and a working passivating aqueous liquid composition
according to the
invention preferably, for reasons of economy of operation, is as short as
possible, consist-
ent with formation of a passivating layer as effective as desired. More
specifically, the
time of contact preferably is not more than, with increasing preference in the
order given,
,s 200, 150, 100, 75, 50, 40, 30, 25, 20, 15, 13, 11, 10, 9.0, 8.0, 7.0, 6.0,
5.0, 4.0, 3.0, 2.0,
1.5, or 1.0 seconds. Spraying a heated working passivating aqueous liquid
composition
onto the surface to be passivated followed by removing excess liquid with a
squeegee has
been found effective in forming a passivated surface according to this
invention within
a few seconds at most.
2o Normally the surface to be passivated preferably is not rinsed with water
or other
diluent between contact with a working passivating aqueous liquid composition
accord-
ing to the invention and drying. Drying can be accomplished by simple exposure
to am-
bient air for a sufficient time, and indeed is preferably accomplished in this
way if the
passivated surface has been formed at a sufficiently high temperature that
drying occurs
as within a few seconds of separation from contact with the working
passivating aqueous
liquid composition according to the invention as described above.
Alternatively, one
may hasten the drying by exposure of the wet surface after passivation to a
higher tem-
perature than the normal ambient temperature, in an oven or by any of the
other means
such as infrared radiant heating, microwave drying, and the like well known
per se in the
30 art.
T'he passivating coating formed in a process according to the invention
includes
molybdenum in sufficient amounts to be detected by X-ray fluorescence.
Preferably, the
9
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WO 97/27001 PCT/LTS97/00012
coating is thick enough that the amount of molybdenum added-on during the
passivation
process, including drying after the contact with a working passivating aqueous
liquid
composition according to the invention corresponds to at least, with
increasing prefer-
ence in the order given, 1.0, 3.0, 5.0, 7.0, 9.0, 10.0, or 10.5 milligrams per
square meter
s of the metal surface passivated (hereinafter usually abbreviated as
"mglm2"), measured
as molybdenum atoms, and if very high corrosion resistance is needed more
preferably
is at least, with increasing preference in the order given, 12, I5, 20, 25,
30, or 32 mg/mz
measured as molybdenum atoms and independently preferably, primarily for
reasons of
economy, corresponds to not more than 100, 75, 65, 55, 50, 45, 40, or 35 mg/mz
mea-
,o sured as molybdenum atoms. The amount of molybdenum added-on may
conveniently
be measured with a commercially available instrument, a PORTASPECTM Model 2501
X-ray spectrograph from Cianflone Scientif c, or by other means known to those
skilled
in the art.
After forming the initial passivating layer as described above, it is normally
pre-
~s ferred to further improve the corrosion andlor staining resistance of the
passivated sur-
face by overcoating it with a protective layer containing at least an organic
binder. Any
of a wide variety of clear and pigmented paints and like materials, as
generally known
per se in the art can be used for this purpose. A particularly useful type of
overcoating
for many purposes is a clear acrylic coating formed by drying into place a
liquid layer
zo of acrylic latex emulsion formed on the initially passivated surface. Such
an overcoating
preferably has a thickness after drying that is at least, with increasing
preference in the
order given, 0.2, 0.4, 0.6, 0.8, or 1.0 micrometres (hereinafter usually
abbreviated as
"gym") and independently preferably, primarily for reasons of economy, is not
more than
10, 7, 5, 3, 2.5, 2.0, 1.5, or 1.3 um. When the passivated surface is to be
used in an appli-
zs cation where a metallic appearance is desired, as in roofing for example,
this relatively
thin clear acrylic overcoating can serve adequatelyas the final coating layer
in many in-
stances. For more severe service, additional thicker coatings of paint and
Like materials
adapted to a specific purpose as known per se in the art may be applied
directly over this
initial thin acrylic overcoating, or directly over the passivated metal
surface itself.
so Before passivating according to this invention is to be used for any metal
sub-
strate, the substrate to be passivated is preferably thoroughly cleaned by
arty of various
methods well known to those skilled in the art to be suitable for the
particular substrate
CA 02242995 1998-07-14
WO 97/27001 PCTlUS97/00012
to be coated.
The practice of this invention may be further appreciated by consideration of
the
following, non-limiting examples, and the benefits of the invention may be
appreciated
by contrast with the comparison examples set forth below and additional
comparisons
s known to those skilled in the art.
~renaration of Concentrate Make-Up Compositions Accordin~~to the Invention
The amounts of materials shown in Table 1 were used to make five concentrates
according to the invention.
TABLE i
Ingredient Parts
of
Ingredient
in
Composition
#:
C-1 C-2 C-3 C-4 C-5
Deionized Water 583 354 549 320 226
75 % Aqueous H3P04 114 343 114 343 114
Starch 11.4 I1.4 45.7 45.7 14.3
~s Molybdenum Trioxide 91.4 91.4 91.4 91.4 45.7
All the materials shown in Table 1 except the Mo03 formed a solution, which
was boiled
in contact with the solid Mo03 for one hour or until alI the Mo03 had
dissolved. Tliiis
produced a concentrate composition with a dark blue color but no visually
apparent sepa-
zo rate solid phase. These concentrates had the characteristics shown in Table
2.
TABLE 2
Characteristic Value
of
Characteristic
in
Composition
#:
C-1 C-2 C-3 C-4 C-5
Specific Gravity 1.i8 1.35 1.19 1.37 1.26
zs % of Mo Atoms with Valence3.15 7.7I 9.36 19.6 I5.8
< 6 ~ ~ I ~ I
Working Compositions According to the Invention
' The first four of the concentrate make-up compositions as described above
were
used to prepare working compositions that contained 10 % by volume of the
liquid co~n-
so centrate make-up compositions. In some instances, aqueous fluozirconic acid
was also
11
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WO 97/27001 PCT/US97/00012
added to the working compositions, to produce the working composition
concentrations
shown in Table 3 below.
TABLE 3
Working Grams
C per Liter
i in Working
i Composition
of:
-
ompos PO,~ 3 Mo as Mo03 Starch HZZrF6
t Ions
on
Number
W-1.1 12.3 I3.4 1.6 none
W-1.2 12.3 I 3.4 1.6 0.45
W-2.1 42.7 15.6 1.6 none
W-2.2 42.7 15.6 1.6 0.45
W-3.1 12.3 13.4 7.8 none
W-3.2 12.3 13.4 7.8 0.45
W-4.1 42.7 15.6 7.8 none
W-4.2 42.7 15.6 7.8 0.45
Passivatin~ Processes
Test panels of GALVALUMETM sheet, which is steel sheet coated with an alloy
of 55 % Al, 1.6 % Si, and 43.4 % AI and is a product of Bethlehem Steel
Corporation,
were cleaned in a cleaning solution prepared from PARCO~ Cleaner 338, which is
a
s commercial cleaner recommended for cleaning aluminiferous and zinciferous
surfaces,
is available from the Parker Amchem Division of Henkel Corporation, Madison
Heights,
Michigan, USA, and was used according to the manufacturer's directions. The
cleaned
panels were then rinsed with water and subsequently immersed for a period of
time noted
below in a working composition according to the invention, which was
maintained at a
~o temperature of 49 to 54 °C, or in a comparison passivating
composition as also described
below. The passivated panels were then removed from contact with the
passivating com-
position and allowed to dry in ambient air. Drying was complete within 5
seconds. In
some instances as shown in the Tables, the thus gassivated and dried surfaces
were fur-
ther coated with a mixture of 50 % each of RHOPLEXTM HA-16 and AC-73 acrylic
latex
Y
,s emulsions. (These emulsions were commercially supplied by Rohm & Haas
Company.)
The thickness of the acrylic coating was controlled to be equivalent to 1.0 ~
0.2 pm after
12
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WO 97/2?001 PCTlUS97/00012
drying, and the coating was then dried into place on the passivated surface
without rins-
ing. Panels were then physically tested. Some results are shown in Tables 4
and 5.
TABLE 4: RESULTS OF ASTM D45$5-87 TEST ("CLEVELAND CONDENSATION",1
Process Working Passi- Test Results osure
After Time
Exp Showrn:
-
Test Compo- eating Without With
Number sition Time, Acrylic Acrylic
Coat Coat
Used Seconds 72 Hrs 672 72 Hrs 672
Hrs Hrs
1 W-1.1 5 4 n.m. 10 9
2 W-1.2 20 6 1 1 6
3 W-2.1 30 4 n.m. 10 8
4 W-2.2 20 4 n.m. 10 9
5 W-3.1 n.r. 5 n.m. 10 8
6 W-3.2 n.r. 6 0 10 10
7 W-4.1 n.r. 2 n.m. 10 6
8 W-4.2 n.r. 1 n.m. 10 5
9 See Note n.lc. 10 10 n.a. n.a.
I
10 See Note n.r. n.a. n.a. 10 10
2
Numbered Notes for Table 4
1. This process, which was not according to the invention, used commercially
sup-
plied "mill passivated" panels from National Steel Corp., which are believed
to have been
passivated by a process requiring the use of hexavalent chromium.
2. This process, which was not according to the invention, utilized a
conventional
prior art mixed hexavalent chromium and acrylic emulsion passivating process;
it did not
have a separate acrylic coating thereafter, but because of the presence of
acrylic in the
passivating layer itself, the results are listed under the column "With
Acrylic Coat".
Abbreviations for Table 4
ASTM = American Society For Testing and Materials; Hrs = Hours; n.m. _ not
measured; n.r. = not recorded, but estimated to be 20 to 30 seconds; n.k.. =
not known;
n.a. = not applicable.
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WO 97/27001 PCT/US97/00012
TABLE 5
RESULTS OF "STACK TEST" AT 70 °C AND 100 % RELATIVE HUMIDITY
Process Acrylic Rating
T T after
t C Exposure
for:
- -
es op -
Number oat 168 Hours 336 Hours 504 Hours672 Hours
Used?
11 * No 9 n.m. n.m. 6.7
12* Yes 10 10 10 10
See Note n.a.. 10 9.0 8.0 4.3
1
See Note n.a.. 10 10 10 10
2
Numbered Notes for Table S
1. This process, which was not according to the invention, used commercially
supplied "mill passivated" panels from National Steel Corp., which are
believed to have
been passivated by a process requiring the use of hexavalent chromium.
2. This process, which was not according to the invention, utilized a
conventional
prior art mixed hexavalent chromium and acrylic emulsion passivating process.
Footnote for Table 5
*The working composition according to the invention used for this process test
was made
in the same general manner as described above for other working compositions
according
to the invention, but it contained 12.1 g/L of P04 3 ions from H3P04 used in
making the
corresponding concentrate make-up composition, 6.7 g/L of molybdenum, measured
as
its stoichiometric equivalent as Mo03, 1.7 g/L of starch, and no other
ingredients except
water, counterions, and reaction products of the four ingredients (i.e.. H,O,
H3P04,
Mo03, and starch mixed to make the concentrate.
her Note for Table 5
In the "stack test", an assembly of six panels is placed one atop another so
that passivated
sides are touching each other, then exposed in a controlled atmosphere cabinet
to the
conditions noted in the title of the table. After exposure, the passivated
surfaces were
separated and examined visually. The ratings are on a scale of 0 (worst,
completely
blackened surface) to 10 (best, no staining or other discoloxation of the
surface).
In addition to the tests noted in Tables 4 and 5, a panel prepared in the same
manner as for Process Test 12 in Table 5 and three controls, specifically an
unpassivated
sample and samples treated in the same manner as in numbered notes 1 and 2 in
Table
S were tested by exposure to steam and water: Each panel tested was used to
cover a
beaker in which water was boiling from a liquid volume of one-fifth to one-
half of the
total capacity of the beaker, with the tested surface of the panel facing
down, so that it
functioned as a reflux condenser for the steam boiling from the water below.
The unpas-
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WO 97/27001 PC~'/CTS97100012
sivated test panel turned black within 5 minutes of exposure to these
conditions, while
the other three panels mentioned remained unblackened after 30 minutes of such
ex-
A
posure.
