Note: Descriptions are shown in the official language in which they were submitted.
1~79164
Back~round Of The Invention
P~osphatizing operations carried on in water have typirally
provided drawbac~s, including sludging and the ~eed for a multi-
~tep operation, to achieve dry, coated articles. In an early
attempt to overcome such problems, a~ described in U.5. Patent
2,515~934, from 13 to 7% of the commercial phosphoric acid 85%
syrup was used in an orga~ic mixture, rather than in water.
Representative of these mlxtures was a S0/50 blend of acetone and
carbon tetrachloride. With the blend, only z few steps were
needed for phosphatizing.
A different approach to overcoming the problems that are
found in water-~ased phosphatizing systems, was taken in the
process of U.S. Patent 2,992,14~. Therein, by ~eans of special
equipment, an aqueous phosphatizing sol~tion was sprayed onto a
metal artici2, while ~he article was being mainta~ned in a ~aoor
degreas~ng zor.e. The vap~r degreasing zone contair.e~ the vapors
from a chlorinated hydrocarbon such as trichlorethylene. The
operation thereby permit~ed enhancad dry~ng of panels aft~r
phosphatizing.
-1079164
In subsequently developed phosphatizing operations that
relied on using chlorinated solvents, the water solution for the
phosphatizing was altogether eliminated. In typical operations,
a metal article for phosphatizing might be dipped in a chlori-
nated hydrocarbon degreasing solution, then come Ln contact with
a non-agueous phosphatizing solution, and thereafter be returned
to the chlorinated hydrocarbon degreasing solution for a final
rinse operation. Such operation has been descri~ed for example
in U.S. Patents 3,100,728 and 3,197,345. As also discussed in
the 3,197,345 Patent, it was ~ecoming recognized that there was a
water-based process, also called an "aqueous" method of phos-
phatizing metal articles, and on the other hand a solvent-based
process, which was therein noted as the "dry" process. The
latter process typically employed a solution of phosphoric acid
in a chlorinated hydrocarbon solvent. Since the compositions of
the 3,197,345 Patent relied on chlorinated hydrocarbons, the
phosphatizing method used was the ~dry" process and the useful
compositions were substantially water-free compositions.
As early as in the 2,515,934 Patent, it was recoqnized that
the commercial phosphoric acid would introduce a small amount of
water into organic phosphatizing compositions. In the 3,197,345
Patent teachL~gs, it was regarded that substantially all of the
water could be distilled from the phosphatizing bath as t~e "dry"
treatment progressed. Getting away from a dependence on phos-
phoric acid was also explored. From this, it was found th~t
special orsanic phosphate complexes could be useful i~ the non-
aqueous solutions. They had the ad~antage of pro~iding pro-
tective coatings of enhanced corrosion ~esistance. This approach
was taken in U.S. Patent 3,249,471. A~othe_ approach t~ the d~y
process, or to the "non-aqueous" process as it was also called,
and that was employed in U.S. Patent 3,297,49~, was the use o~ a
high strength acid. In such Patent, the acid used was pre erably
1()79164
one of 96-100% phosphoric acid. This concentrated acid presented
sludge problems, but these were overcome by employing special
additives.
Other techniques, to maintain the non-aqueous phosphatizing
process "dry", included the use of drying agents such as magne-
sium sulfate and the use of powdered metals. These concepts have
been discussed in U.S. Patent 3,338,754. Therein it was empha-
~ized that small amounts of water are detrimental to the phos-
phate coatings obtained from the non-a~ueous phosphatizing solu-
tions. It was also early recognized in the 2,515,934 Patent that
the presence of water in an organic phosphatizing system could
lead to the formation of two li~uid phases, with attendant prob-
lems developing. Phase separation, and especially with regard to
the formation of a separate aqueous phase, was discussed in U.S.
Patent 3,306,785. It is also noted, from the ~,306,785 Patent,
that in developing the "dry" process with chlorinated hydro-
c~ bons, emphasis was being placed on the commercially important
trichlorethylene and perchlorethylene solvents.
SummarY Of The Invention
It has now been found that a chlorinated hydrocarbon phos-
phatizing composition can produce highly desira5le coating when
such composition is maintained in a more "wet" condition. An
iritial key ingredient for ~he composition is methylene chloride.
A further critical ingredient, in addition to a phosphatizing
proportion of phosphori~ acid, is an amount of water exceedir.g
such proportion of phosphoric acid. But such water is not
present in sufficient amount to provide a liauid composition that
does not retain liquid phase homogeneity. ~oreover, it has now
~een found possible to inc~ease the coating weight of the resul_-
ing phosphate coating, by increasing the water content of the
phosphatizir.g composition well beyond a content of just mi..ute
amounts.
10791~4
A further and most significant discovery, is the achievement
of phosphatized coatings of extremely reduced water sensitivity.
Because of this, phosphate coatings are now achieved wherein the
coatings can be successfully topcoated with water based compo-
sitions. Such compositions can include a~ueous chrome rinses.
They can additionally include such coatings as wate~ reduced
paints and electrocoat primers. With the ingredients that are
Ln the phosphatizing composition, including a solubilizing sol-
vent capable of solubilizing the phosphoric acid in the methylene
chloride, it has furt~ner been found that a vapor zone can be
achieved in connection with the phosphating solution, in which
zone there is obtained enhanced rinsing. For example, with the
solubilizing solvent metnanol, an especially desirable vapor zone
can be obtained.
Liquid blends that can include methylene chloride, methanol
and water as a portion of the blend have been known heretofore.
Further, the methylene chloride/methanol and methylene chloride~
water azeotropes have been recognized to have nearly adjacent
boiling points. Such recognition has been siven for example in
U.S. Patent 3,419,477. As in the 3,419,477 Patent, tiese pheno-
mena have been previously recognized as useful in separation
techni~ues. That is, separation of components can at least be
initiated by making usa of the azeotrope phenomena. ~ow, how-
ever, it has been found that in the vapor zone, c~eated through
the use of the phosphatizing compositions of the present inven-
tion, the vapor can provide for excellent rins ng of phosphate
coated articles. Moreover, on condensation, ~ne licuid conaense~
from the zone will retain complete liquid phase nomogeneity ,
without phase separation.
As a corollary, bath reju~enation, for example, can be
accomplished by introducing into the phosphat zlng batn a ur.ifor~
li~uid. This liquid, in constituency, can be equated to the
1079164
constituency of the vapor zone; it thus will be a homogenous
blend. The blend is amenable to preparation for storage and/or
handling, without loss of liquid phase homogeneity, prior to
use as bath replenishing liquid.
Broadly, the invention is directed to a methylene-
chloride and water-containing liquid composition having a
continuous and homogenous liquid phase. The composition is
suitable for phosphatizing metal with a water-resistant coating,
while the liquid phase contains water in minor amount. More
particularly, the composition comprises methylene chloride,
solubilizing solvent capable of solubilizing phosphoric acid
in methylene chloride, a phosphatizing proportion of phosphoric
acid, and water in an amount exceeding the proportion of
phosphoric acid while being sufficient for the composition to
provide a phosphatized coating of substantial water insolubility,
and while retaining liquid phase homogeneity.
Another aspect to the invention is the process of
providing a phosphate coating, of the nature described herein-
above, by contacting a metal surface with a composition having
a continuous and homogeneous liquid phase and containing water,
in a minor amount, with the composition further containing sub-
stances as described hereinabove. Such process may further
include contacting of the metal surface, before the phosphatizing
with vapors containing methylene chloride, and may also include
contacting, after the phosphatizing, of the coated metal
surface with vapors containing methylene chloride.
Thus, in accordance with the specific teachings of
the present concept, a coated ferruginous substrate is provided
which has an adherent and water-insoluble surface coating that
is a complex coating of the iron phosphate type. The surface
coating contains, in addition to trace elements, the elements
iron, phosphorus and oxygen, plus carbon and nitrogen.
-5-
1079164
In accordance with a further aspect, a coated
ferruginous substrate is provided which has a corrosion-
resistant and water-insoluble composite surface coating. The
base coating of the composite on the substrate surface is a
complex coating of the iron phosphate type and contains, in
addition to trace elements, the elements iron, phosphorus and
oxygen plus carbon and nitrogen with the subsequent coating
in the composite being an adherent coating from a non-
phosphatizing solution for treating metal surfaces.
Additional aspects of the invention include any of
the foregoing phosphatizing processes followed by an aqueous
chromium-containing solution treatment of the phosphatized
metal surface. Other aspects of the invention include a
vapor-containing rinse zone, for rinsing phosphate coated
panels that have been in con-
-5a-
1079164
tact with thephosphatizing liquid, with such zone comprising 2
mixture of methylene chloride vapors, solubilizing solvent vapors
and water vapor.
A still further aspect of the invention is a composition Lor
sustaining phosphatizing from a phosphatizing li~uia medium lS
above described. Such rejuvenating composition includes, in a
homogeneous liquid blend, ingredients also found in the above-
described, vapor-containing rinse zone.
Description Of The Preferred Em~odiments
The methylene chloride, or the "methylene chloride con-
stituency" a~ it is sometimes referred to herein, is ty~ically
comercially available methylene chloride, and may contain addi-
tional ingredients, although the use of a more purified methylene
chloride is contemplated. The methylene chloride may then con-
tain very minor amounts of stabilizers such as cyclohexane. Use-
~ul, commercially available methylene chloride may contain very
mlnor amounts of additional substances such as cther chlorinated
hydrocarbons, including chloroform and vinylidene chloride. It
is further contemplated to use as the methylene chloride con-
stituency, methylene chloride blended with a minor amou~t of
additional solvent. This would be solvent in addition to the
organic solvent discussed in greater detail hereinbelow. Pre-
ferably, the additional solvent will be non-flammable and will
form an azeotrope with the methylene chloride on heating, e.g.,
trichloro tri~luoroethane. Although the methylene chloride
constituency will generally provide the major amcunt of the
liquid phosphatizing solution and w-ll typically provide between
about 60 to about 90 weight percent or such solution, t~is is not
always the case. Most always, when the methylene chloride con-
stituency does not form the major amount of the solution, thesolubilizing sol~ent will be the pred~minant substi.uent in ~e
solution.
107~1~;4
The solubilizing solvent needs to be one or a mixture that
is capable of solubilizing phosphoric acid in methylene chloride.
The solvent can also affect other characteristics of the phos-
phatizing solution, e.g., the solvent may have an effect on the
solubility of water in the phosphatizing solution. It is advan-
tagecus that the solubilizing solvent not create a readily flam-
mable phosphatizing liquid. It is preferable that it effect
enhanced solubilization of water in the methylene chloride. It
is further preferred, for efficient phosphatizing operation, that
the solvent have a boiling point higher than the boiling point
of methylene chloride, or that the solvent, on boiling, form an
azeotrope with methylene chloride. The solvent can be, and on
occasion most desirably is, a blend of organic substances. Such
blends are particularly useful for augmenting the solubility of
water in the phosphatizing solution.
Particularly where the phosphatizing solu~ion will be used
as a li~uid phosphatizing bath, at elevated temperature, thereby
forming a rinse zone immediately above the bath that contains
constituents of the bath in vapor state, it is desirable that the
solubilizing solvent be present in such vapor. When phosphatized
metal articles are removed from the phosphatizing ~ath into such
rinse zone, one ingredient that may be present on the article for
rinsing is phosphoric acid. Since methylene chloride even as a
vapor in the rinse zone will exert little solubilizing activity
towards the phosphoric acid, it is desirable to have solvent
vapor also present in the rinse zone.
~ ost advantageously for efficiency of operation t~e solu-
bilizing solvent is an alcohol havins less than si~ carbon a~oms.
Alcohols of six carbon atoms or more may be used, but should
always be present in m1nor amount with at least one less t;-an
six carbon atoms alcohol being in major amount. Representative
alcohols that can be or have been used include methanol, eth2nol,
107gl64
isopropanol, n-pentanol, n-propanol, n-butanol, allyl alcohol,
sec-butanol, tert-butanol and their mixtures wherein li~uid phase
homogeneity is maintained when in mixture with methylene chlo-
ride. However, additional substances, e.g., 2-butoxyethanol, can
also be serviceable, alone or in combination with alcohol. As
mentioned hereinabove, useful phosphatizing solutions can be
achieved when the solvent provides the predominant constituent of
the phosphatizing composition. Preferably for efficiency and
economy the organic solvent is methanol.
As inferred hereinabove, phosphoric acid has only an ex-
tremely limited solubility in methylene chloride. However, this
situation is obviated by using the solubilizing solvent. There-
fore, although the phosphoric acid is a critical ingredient that
is generally present in a very minor amount, with the solubil-
izing solvent present in the phosphatizing solution the phos-
phoric acid may be contained in the phosphatizing solution in
substantial amount. Such amount might be up to 2-3 weight per-
cent or more. But, for efficient and economical coating opera-
tion, the phosphoric acid is generally used in an amount below
about one weight percent, basis total weight of the phosphatizing
composition. A much greater amount than about 1~, will typically
leave a coating on the metal substrate that is tacky to the
touch. Preferably, for most efficient coating operation, the
phosphoric acid is present in an amount between about 0.2-0.8
weight percent, basis the phosphatizing solution, although an
amount below even 0.1 weight percent _an be ser~iceable.
If it is contemplated that the phosphatizing solution wili
be used for the coating of metals that have been heretofore
rec~snized as susceptible to phosDhatizing, .e., capable of
reacting with phosphoric acid. Thus, it is contemplated that ~he
phosphatizing solution will be userul for phosphatizing aiu~i~m,
zinc, ca~mium and tin substrates as well as the more typical
1079164
ferruginous metal substrates. The "phosphatizing proportion of
phosphoric acid", as such term is used herein, may well be a
"phosphatizing substance", as it might more appropriately be
termed. That is, the use of such terms herein is not meant to
exclude any substances that may be, or have been, useful in the
solvent phosphatizing art for providing a phosphate coating.
Such s~bstances might thus include organic phosphate substanca as
well as the more typical acidic substances of phosphorous, e.g.,
the usual orthophosphoric acid. Purther, it is contemplated that
such substance include salts of such acids in phosphatizing.
Since water is present in the phosphatizing solution in amounts
greater than the phosphatizing substance, although concentrated
acids are contemplated, e.g., phospholeum, the resulting solution
contains the acid in dilution in water. Preferably, for economy,
the orthosphosphoric acid is always the phosphoric substance used
in the phosphatizing solution.
As mentioned hereinbefore, the amount of the phosphatizing
substance in the phosphatizing solution is exceeded by the
amount of water present in such solution. Water must be present
in at least an amount sufficient to provide a phosphatized coat-
ing on ferrous metal of substantial water insolubility. As is
discussed i~ greater detail hereinbelow, this means that the
coating will be, at most, about 20% water soluble. On the other
hand, water may typically be present in an amount as çreat as
water saturation of the phosphatizing solut~on, at the tempera-
ture of phosphatizing. ~owever, saturation is ~ot exceeded as the
solution will then lose liquid phase homogeniety. ~omogeniety as
used herein refers to solution ~niformity free from liquid phase
separation. When water separates, the separate wate phase may
attract phos~horic acid into such phase, to the detriment of
further coating operatior..
1079164
Por many phosphatizing solutions of the present invention,
on one hand water insoluble coatings are achieved, coupled with
an acceptable coating weight, when the water content of the solu-
tion reaches about 1.5-2.5 weight percent. On the other hand,
phase separation for many solutions can occur when ~he water con-
tent reaches about 5-7 weight percent, basis total solution
weight. Such is shown in greater detail, by reference to the
Examples. But, since the solubilizing solvent can affect the
ability of a phosphatizing solution to solubilize water, then
especially those solutions wherein the solubilizing solvent
predominates, may be solutions able to contain substantial
amounts of water, for ex~mple 10-25 weight percent of water
might be reached without achieving saturation. But the water
will always provide a minor weight amount of the phosphatizing
~olution.
Water in the solution will exert a vapor pressure: the solu-
tion water content will thereby directly influence the water con-
tent of the vapor zone associated with the solution. When such
zone is over a bath of phosphatizing solution, a substantial
amount of water vapor may retard the drying time of coated metal
su~strates that are phosphatized in the bath and then removed to
the vapor zone for drying. Thus attention to the water content
of a bath, when such might exceed about the 5-10 weight percent
range is advisable. Since water is present in the phosphatizing
solution in an amount in excess of p~.osphor c acid, it will most
always be present in an amount within the range of abou~ 2-;
weight percent.
Basic to the 'IphOsphatizing solution" or "phosphati~ing
composition" as such ter~s are used herein, are ~he methylene
chloride constituency, solubilizing solvent, phosphatizing pro-
portion of phosphoric acid, and the wate~ further substance
10~9164
that may be present in the phosphatizing solution is an aprotic
organic substance. Although it is contemplated to use aprotic
polar organic compounds for such substance, it is pre~erred for
efficient coating operation to use dipolar aprotic organic com-
pounds. These compounds act in the coating solution to retard
the formation of an undesirable, grainy coating. The aprotic
organic compound can also influence the level at which water
satu ation will occur in the phosphatizing compositions contain-
lng ~uch compound, particularly when they are present in substan-
tial amount. Although it is contemplated that such compound willalways be present in minor weight amount of the phosphatizing
solution, and generally present in an amount less than the amount
of the solubilizing solvent, serviceable phosphatizing solutions
can be prepared th~t contain on the order of ten to fifteen
weight percent or more of such aprotic organic compound.
It is prsferred, for extended retention of the aprotic
organic compound in the phosphatizing qolution during the phos-
phatizing operation, that such compound have a boiling point
above the boiling point of the methylene chloride. Preferably,
for most extended presence in the coatir.g solu~ion, such compound
boils at least about 20~C higher than the methylene chloride.
The aprotic organic compound is often a nitrogen-containing
compound; these plus other useful compounds include N,N-di~ethyl
formamide, dimethyl sulfoxide, ace.onitrile, acetone, nitro-
methane, nitrobenzene, tetramethylenesulfone ~nd their inert and
homogeneous liquid m ~tures where such exist. 3y being inert, it
is meant that such mixtures do not contain substituents that ~ 11
chemically react with one another, in the phosphatizing solution,
at the temperature attained for the solution to be at boiling
condition. Dimethyl sulfoxide is useful as an aprotic or~anic
compound; but, such may further be used as an accelera~or com-
pound, as is discussed h~rein below. In such case when the
1079164
dimethyl sulfoxide is present as an accelerator compound, sub-
stance other than dimethyl sulfoxide is used to supply aprotic
organic compound.
Ano~her substance generally found in the phosphatizing com-
position is the organic accelerator compound. Such compound
serves to increase the rate of formation of the coating during
the phosphatizing process. Acceleration is accomplished without
deleteriously affecting the nature of the coating, e.g., desir-
able uniform and non-grainy crystal structure for the coating.
Serviceable compounds typically act in such manner even when
present in the composition in very minor amount, as for example,
in amount much less than one weight percent basis total composi-
tion weight. Advantageously, for efficient operation, the
accelerator compound has a boiling point greater than the boiling
point of methylene chloride. Many of the useful accelerator
compounds are nitrogen containing organic compounds. More speci-
fically, compounds that can be, or have been, used include urea,
pyridine, thiourea, dimethyl sulfoxide, dimethylisobutylene
amine, ethylenediaminetetraacetic acid and dinitrotoluene.
The use of stabilizers has been taught in the prior art and
such are contemplated for use herein, such as the hydrogen and
hydrogen chloride acceptor substituents that can retard the
corrosive nature o phosphatizing compositions. Stabilizers
against oxidation of a halohydrocarbon, for example, are also
kn~swn. These can likewise assist in reducing the corroslve
nature of the phosphatizing composition. Useful substancss can
include p-~enzo~uinone, p-tertiaryamyl phenol, thymol, hyd-o-
quinone and hydroquinone monomethyl ether.
The methylene chloride containing phosphatizir.g composition
is suitable for use with any of the phosphatizing operations tnat
can be, or have been, used with solvent phosphatizing. Solvent
phosphatizing operations can provide, quickly and e ficiently,
1079164
dry, coated metal substrates; and thus, such operations will most
always provide for quickly achieving same. Sequentially, metal
articles for phosphatizing may be typically degreased in methy-
lene chloride degreasing solution and then immersed in a bath of
the phosphatizing composition with such bath being most always
heated to boiling condition. The phosphatized article, upon
removal from the bath, can then be maintained in the vapor zone
above the bath for evaporating volatile constituents from the
coated article to coating dryness. During such maintenance, the
article may be subjected to a spray rinse. The phosphatizing
composition may also be spray applied to a metal article, such as
in 4 vapor zone that might be formed and/or replenished by vapor
from the spray composition. Other contemplated aspects of suc-
cessful operation include initial rinsing of a metal article with
warm rinse liquid, e.g., immersion rinsing in such liquid, where-
in the liquid is formed from the constituents of the vapor from
the phosphatizing 901ution. Such rinsing is then followed by
phosphatizing, and this can be further followed by an additional
rinse in the warm rinse liquid. For e4ficiency in all opera-
tions, the temperature of the phosphatizing composition is ma n-
tained at boiling condition. At normal atmospheric pressure this
will typically be at a temperature within the range of about 100-
105P. although lower temperatures of operation are contemplated.
In the ambient atmosphere adjacent to the phosphatizing solution,
constituents of such solution may be present in the vapor state.
For convenience, this atmospheric region is there~y termed ~he
~vapor zone".
During phosphatizing, which will take place typically in
degreaser apparatus, the vapor zone, in addition to containing
trace amounts of other substances, will be found to cor.tain
methylene chloride vapor, vapor from the solubilizing solven'
that solubilizes the phosphoric acid in methylene chloride as
1079164
well as water vapor. Since such substances are the chief in-
gredients of the vapor zone, they are the chief ingredients of
the phosphatizing composition that can be expected to be los~
from such composition as vapor loss. It has therefore been found
to be most serviceable to formulate a replenishing liquid com-
position containing methylene chloride, solubillzing solvent and
water. Further, it has been found that such replenishing liquid
can be successfully ussd for sustaining the phosphatizing com-
position, and that such can form a homogeneous and storage-stable
blend. Thus, for convenience, this li~uid is often referred to
herein as the "sustaining solution." The sustaining solution can
be prepared ahead, for later use after storage and/or shipment.
It can be useful for sustaining the formation of water-resistant
and uniform coatings, especially when used for in-ser~ice phos-
phatizing solutions. The coatings from in-service solutions might
be exhibiting loss of coating uniformity, for example.
In the make-up of the sustaining solution, the methylene
chloride will be the predominant ingredient, generally supplying
between 70-97 weight percent of the solution. In the balance, the
solubilizing solvent will supply the major amount, being usually
present in an amount between about 2-25 weight percent of the
total solution. The water is present in minor amount, e.g. 0.5-2
percent or less, and always together with suf'icient solubilizing
solvent to insure solution homogeneity. For the preferred sol-
vent methanol, the sustaining solution will preferably contain,
for best sustaining action, between about 90-96 percent methylene
chloride, about 2-9 percent methanol and 0.4-4 percsnt water, with
the three components totalling 100 weight percent. Preferably,
for enhancad phosphatizing operation, the water, solubilizing
solvent and methylene chloride will be combined in the sustainin~
solution in the equivalent proportions of such substances in the
phospha~izing medium vapor zone. To erficiently prepare a homo-
107916g
geneous sustaining solution, it is preferred to first preblendthe water with solubilizing solvent. Then the methylene chloride
iq admixed with the preblend to quickly obtain a homogeneous
sustaining solution. In the preferred method of preparation, and
for the preferred solubilizing solvent methanol, the weight ratio
of the water to the alcohol in the preblend is generally main-
tained at less than 1:6. Often, such ratio will be on the order
of 1:10-1:12. Also in this preferred method of preparation,
after the methylene chloride addition, additional ingredients, if
pre-~ent, are then generally added.
These additional ingredients will be present in very minor
amounts. Typically these are present in combination in an amount
less than about 1-2 weight percent based on the weight of the
sustaining solution. Such ingredients can include accelerator
compound, stabilizer compound, aprotic organic compound and
phosphoric acid. ~owever, where such sustaining composition is
prepared for extended storage, the phosphoric acid is generally
not ~ncluded to avoid the use of special, acid-resistant con-
tainers. Preferably, for economy, the additional ingredients are
each present in an amount less than about 0.1 weight percent.
For the preferred solvent methanol, in addition to the
constituency of the sustaining solution being as described above,
it is furthe~ advantageous for most efficient coating action that
such solution be added to the phosphatizing medium so as to
maintain the medium at a specific graYity between about 1.14 and
about 1.17. At a specific gravity below about 1.14, commercially
desirable coatings may not be efficiently achieved, while at a
phosphatizing medium specific gravity greater than about 1.17,
when the solubilizing solvent is methanol, coating formation can
require undesirably delicate control. P-eferably, for best
phosphatizing from a methanol containing medium, the sustaining
solution is used to maintain the medium specific gravity between
about 1.15 and about 1.16.
1079~64
As a pre-packaged blend, the sustaining solution in addition
to being useful for sustaining, has further utility in the make-
up of a fresh phosphatizing composition. When using the sus-
tain~g sol~tion for fre-eh solution make-up, it has been found
that typical additional ingredients for the solution make-up may
also be prepared ahead in a storage-stable and uniform blend.
This additional blend will generally contain, as chief ingre-
dients, solubilizing solvent, aprotic organic compound and water.
Further, such additional blend will often contain accelerator
compound and sta~ilizer compound. Such blend is often referred
to herein sLmply as the precursor composition. n As a precursor
composition to the make-up of a fresh bath, substances are gen-
erally simply mixed together for preparing this precursor com-
position and then the composition is pac~aged for storage and/or
handling. Most usually, the solubilizing solvent will comp~ise
the major amount of this precursor composition, and preferably
will supply between about 55-80 weight percent of the composi-
tion. Further, the water and aprotic organic compound may be
present in substantially equivalent amounts. Each ingredient
will generally be present in an amount between about 10-30 weignt
percent. Additional ingredients, e.g., accalerator compound or
stabilizer compound, are each often present in an amount less
than one weight percent, basis the weight of such precursor
composition. In a typical fresh bath maXe-up, the precursor
composition and the ab~ve described sustaining solution, with one
or both of such generally containi~g accelerator plus stabillzer,
are mixed together, often for use in degreasing apparatus, with
phosphoric acid being added during the blending. Thus, only
these two solutions plus phosphoric aci~ need be on hznd at the
inception or phosphatizing solution ma~e-up.
After coating formation on a metal a-ticle, the article c~n
then proceed into a vapor zone that will be su~plied and re?len-
107gl64
ished by vaporized substituents from the phosphatizing composi-
tion. As discussed herein before, such vapor zone can have a
highly desirable make-up of methylene chloride vapor, water vapor
and solubilizing solvent vapor as chief constituents. This vapor
blend has been found to be highly suitable as a rinsing and
drying medium for phosphatized articles. Typically, as in immer-
sion ph~sphatizing, the coated article may be simply removed from
the phosphatizing bath into the vapor zone, maintained in such
zone until dry, and then removed for subsequent operation. The
constituency of the vapor zone, in addition to supplying a desir-
able rinsing medium, will also form, on condensation, a stable,
uniform liquid blend. This phenomenon enhances the simplicity of
recirculation systems, as when coating operation is handled in
degreaser apparatus. Also, such recirculation systems can be
adapted to have the recirculating, condensed vapor replenished
with fresh sustaining solution, which solution has been discussed
hereinabove, with the replenished liquid then being recirculated
to the phosphatizing solution medium.
As such medium in this operation will typically be main-
tained at a temperature at boiling condition, the temperatu~e at
the vapor zone will typically be within the range of about 100-
105F. Further, the methylene chloride will form the predominant
substance in the vapor zone. For example, in a phosphatizin~
composition wherein methanol is the solubilizin~ solvent, the
vapor zone can ~e expected to contain above 90~ by weight of
methylene chloride, exclusive of the ambient air in such zone.
But, because the vapor zone will also contain methanol vapor, as
well as water vapor, such combination insures a highly desirable
rinse vapor. ~ore particularly, with the methanol as solvent,
the vapor zone at normal pressure may be at a temperature from
about 101F. to about 104F. and contain betwee~ about 0.6-0.7
1079164
weight part water, with between about 5.5-6.5 weight parts meth-
anol and the balance methylene chloride to pro~ide 100 weight
parts.
The phosphatizing composition will typically provide a
desirable phosphate coating, i.e., one having a weight of twenty
milligrams per s~uare foot or more on ferrous metal, in fast
operation. Although contact times for ferrous metal articles and
the phosphatizing composition may be as short as fifteen seconds
for spray application, it will typically be on the order of about
forty-five Qeconds to three minutes for dip coating, and may even
be longer. The coating weights, in milligrams per square foot,
can be on the order as low as ten to twenty to be acceptable,
i.e., provide incipient corrosion protection with initial en-
hancament of topcoat adhesion, and generally on the order of as
great as one hundred to one hundred and f i f ty although much
greater weights, e.g., three hundred or so, are contemplated.
Preferably, for best coating characteristics including augmented
topcoat adhesion and corrosion protection, the coating will be
present in an amount between about 20-100 milligrams per square
foot. Such coatings are readily ar.d consistently produced with
desirable coating uniformity.
The coatings that are obtai~ed on ferrous metal will have at
least substantial water insolubility, and hence are also termed
herein to be "water-resistant" coatings. For determining wat~r
solubility, the test employed is sometimes referred to as the
"water soak test". In this test, as is also described in con-
nection with the examples, a coated ferruginous article is
weighed and then immersed in distilled water for ten minutes.
The water is maintained at room temperature, ~ypically 65-75F,
and with no agitation. After this ten minute Lmmersion, the
article is remo~ed from the water, rinsed in acetone and air
dried. Subsequently, on re-weighing, the amount of water sol~-
~07916~
bility of the coating is shown by any weight loss. This loss isgenerally expressed as a percentage loss of the total original
coating. The method used for determining the original coating
weight has been more specifically described in connection with
the examples.
Ad~antageously, for enhanced corrosion protection, the water
solubility of the coating will ~e on the order of less than 20~
as deter~ined by the water soak test. Such a coating, for con-
venience, is often termed herein as a "phosphatized coating of
substantial water insolubility". Preferably, for best coating
per'ormance, including the ability to receive topcoating with
water-based topcoat compositions, the water solubility of the
coating will be less than 5%, basis total weight of the original
coating. In typical processing, the phosphatizing operation of
the present invention will pro~ide phosphatized coatings on
ferruginous surfaces ha~ing virtually no water solubili~y as
determined by the water soak test.
For better determining the nature of the coatings that are
obtained on ferrous substratos, in addition to physical charac-
teristics, they have been subjected to further coating analysis.As detailed more specifically in the examples, coztings from the
phosphatizing operation that are o~ the iron phosphate type have
been sub~ected to analysis by the Electron Spectroscopy for
Chemical Analysis ~ESCA) technique. Further, such coatings have
been subjected to Auger Spectroscopy. Por convenience, these may
be referred to simply as nspectroscopic analysis". Such analysis
confir~s that the water insoluble coatings, that are o~t~ined in
the phosphatizing operatlon on a ferruginous substrate, contain
in their make-up, the elements sodium and calcium in t ace
amounts. The balance of the elements is pro~ided by phospho-ous,
iron, oxygen, carbon and nit-ogen. Under similar analysis,
comparative pnosphatizea coatings, which are wa~er soluble coat-
--19--
1079164
ings prepared from prior art phosphatizing techniques based onchlorinated hydrocarbon phosphatizing methods, fail to show such
combination of elements in a phosphatized coating. Although all
of the coatings are complex, because of the nature of the spec-
troscopic analysis techni~ues used in analyzing the coating, the
make-up of the coating under analysis is expressed in the form of
the elements. That is, it is to be understood that the coating
is basically and completely defined by setting forth the elements.
Although the elements will or may form various bonding relation-
3hips, the coating is defined by the elements is not limited tovarious particular relationships.
Because of the water resistant nature of the phosphate
coating, the resulting coated metal substrates are especially
adapted for further treatment with water based coating and
treating systems. For example, the coated substrates may ~e
further treat~d with acidified aqueous solutions typically con-
tainlng a multivalent metal salt or acid in solution. Such
treating solutions can contain hexavalent-chromium-containing
substance, including the simplistic rinse solutions of chromic
acid and water as mentioned in U. S Patents 3,116,178 or
2,882,189, as well as their e~uivalent solutions, for example the
molybdic and vanadic acid solutions discussed in U. S. Patent
3,351,504. Purther these treating solutions may be non-a~ueous,
it being contemplated to use chromic acid solutions such as d-s-
closed in U. S. Patent 2,927,046. The treatment can include
solutions containing additional, reactive ingredients, as for
example the combination of chromic acid and formaldehyde dis-
closed in U. S. Patent 3,063,877. Additional treatments that are
contemplated include the complex chromic-chromates from solutions
typically containing trivalent chromium, as has been discussed in
U. S. Patent 3,279,958. Further treatments that can be used
1079164
include such as the blended complex chromate salts disclosed in
U. S. Patent 3,~64,175 as well as solutions containing salts of
other metals, as exemplified in U. S. Patent 3,720,547, wherein
salts of manganese are employed in treating solutions. All of
these trea~ents will generally provide a coating having a weight
of from about 2 to about 40 milligrams per square foot o treated
substrate, although such weight may be lower, and is often
greater, e.g., 100 milligrams per square foot or more. For
convenience, these treatments and solutions collectively are
sometLmes referred to herein as "non-phosphatizing solutions for
treating metal substrates".
The phosphatized coating also lends itself ~o topcoating
from electrically deposited primers, such as the electrodepo-
sition of film-forming materials in the well known electrocoating
processes. Further, the phosphatized coatings can for~ the base
coating for a water reducible topcoating. Such topcoating com-
po~itio~s typically contain solubilized polymers, sLmilar to
conventional alkyd, polyester, acrylic and epoxy types, that are
typically solubilized with smaller amounts of organic amine.
Also the resulting phosphate coated substrate can be further
topcoated with any other suitable resin-containing paint or the
like, i.e., a paint, primer, enamel, varnish or lacquer including
a solvent reduced paint. Additional suitable paints can include
the oil paints and the ~aint system may be applied as a mill
finish.
3efore applying the phosphate coating, it is advisable to
remove foreign matter from the metal surface by clean-ng and
degreasing. Although degreasir.g may be accomplished with commer-
cial alXaline cleanins agents which combine washing and ~ild
abrasive treatments, the cleanins will senerally incl~de de-
greasing. Although such degreasins can be accomplished with
typical degreasing sys~ems, such degreasing can be readily and
efficiently h~ndled ~ith methylene chloride degreasing solvent.
107~164
The following examples show ways in which the invention has
been practiced but should not be construed as limiting the
invention. In the examples all parts are parts by weight unless
otherwise specifically stated. In the examples the following
procedures have been employed.
Preparation of Test Panels
Bare steel test panels, typically 6" x 4" or ~" by 4 n unless
otherwise specified, and all being cold rolled, low car~on steel
panels are typically prepared for phosphatizing by degreasing for
15 seconds in a commercial, methylene chloride degreasing solu-
tion maintained at about 104F. Panels are removed from the
solution permitted to dry in the vapor above tAe solution, and
are thereafter ready for phosphatizing.
Phosphatizin~ of Test Panels and Coatin~ Wei~ht
In the examples, cleaned and degreased steel panals are
pho~phatized by typically immersing the panels into hot phos-
phatizing solution maintained at its boiling point, for from one
to three minutes each. Panels removed from the solution pass
through the vapor zone above the phosphatizing solution until
liquid drains from the panel; dry panels are then removed from
the vapor zone.
Unless otherwise specified in the examples, the phosphatized
coating weight for selected panels, expressed as weight per unit
of surface area, is determined ~y first weighing the coated panel
ard then stripping the coating by immersing the coated panel ir.
a~ aqueous solution of 5% chromic acid which is heated to 160-
180F. during Lmmersion. ~fter panel ~mmersion in the chromic
acid solution for S minutes, the st~ipped panel is removed,
xinsed first with water, then acatone, and air dried. Upon
~0 reweighing, coating weight determinations are readily calculatec.
Coating weisht data is ?resented in milligrams per s~uare foot
(~g/ft2 ) ~
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Mandrel Test Bendinq (ASTM-D 522)
The conical mandrel test is carried out by the procedure of
ASTM D-522. Briefly, the testing method consists in deforming z
paint-coated metal panel by fasteninq the panel tangentially to
the surface of a conical steel mandrel and forcing the sheet to
confonm to the shape of the mandrel by means of a roller bearins,
rotata~le about the long axis of the cone and disposed at the
angle of the conical surface, the angle of deformation or arc
travel of the roller bear~ng being approximately 180. Following
the deformation, a strip of glass fiber tape coated with a pres-
sure-sensitive adhesive is pressed against the painted surface on
the deformed portion of the test panel and is then quic~ly re-
moved. The coating is evaluated quantitatively according to the
amount of paint removed by the adhesive on the tape, in compari-
son with the condition of a standard test panel.
Reverse ImPact Stren~th
In the reverse impact test, a metal ram of specified weight,
in pounds, with a hemispherical contact surface is allowed to
drop from a predetermined height in inches onto the test panel.
20 Paint removal is measured qualitatively or quantitatively on the
convex (reverse) surface. In the qualitative measurement the
Lmpacted surface is merely observed by visual inspection and
comparative panels, i.e., those sub~ected to the same impact in
inch-pounds, are rated according to a numerical scale presented
in Example 6 hereinbelow.
Cross-Hatch
This test is conducted by scribing, through the coatlng to
the metal panel with a sharp .~nife, a first set of parallel lines
one-eighth inch apart. A second, s~miiar set of lines, is then
scribed on the panel at right angles to the first se_. Following
this, a strip of glass fiber t~pe coated with a pressure-sensi-
tive adhesive is pressed asainst the painted surface on .he
107916~
scribed portion of the test panel and is then quic~ly removed.
The coating is rated in accordance with the nlmerical scale
presented in Example 6 hereinbelow, based Ol the amount of paint
removed by the adhesive on the tape.
Coin Adhesion
A fresh nickel coin is firmly secured in vise-grip pliers;
the pliers are manually held in a position such that a portion of
th~ rim of the nickel coin contacts the coated substrate at about
a 45 angle. The nickel coin is then drawn down across the panel
for about two inches. The type of coating flaking and/or chip-
ping is evaluated qualitatively by visual obser~ance, and panels
are compared with the condition of a standard test panel.
EXAMPLE 1
To 288 p~rts of methylene chloride there is added, with
vigorous agitation, 102.4 parts methanol, 1.3 parts ortho phos-
phcric acid, and 1~.8 parts N,~-dinethyl for~amide. These
blended ingredients are thereafter boiled for one hour using a
reflux condenser and the solution i5 permitted to ~ool. The
water content of the resulting boiled solution, provided prin-
cipally by the phosphoric acid, is found to be about 0.1 weightpercent. This water content is directly determined ~y gas
chromatogr~ph analysis of a sample wherein the column pac.~ing is
Porapak Q manufactured by Waters Associates, Inc. The resulting
solution is then heated to 102-103F. and panels are phosphatized
in the manner described hereinabove.
Some of the resulting coated panels, selected in sets of ~o
with each panel in the set being coated ~nder identic~l conditions,
are then subjected to testing. One panel in the set is _sed _or
coating weight determination in the manner described hereinabove.
The other panel in the set is subjected to the water solu~
test. For this test the panel is weigr.ed ~d then immersed in
distilled water for ten minutes, the water bei..g naintained at
1()79164
ambient temperature and with no agitation. Thereafter, the test
panel is removed from the water, rinsed in acetone and air dried.
Subsequently, on reweighing, the amount of water solubility of
the coating is shown by the weight loss. This loss, basis total
original coating weight, is reported in the Table below as '.he
percentage or degree, of coating loss.
Coating weights and water solubility of coatings, are deter-
mined initially for test panels that have been phosphatized in
the above-described phosphatizing composition. Such data are
determined thereafter for additional coated panels that have been
phosphatized in compositions of differing water contents, all as
shown in the Table below. These baths of varying water content
are prepared in step-wise fashion by startinS with the above-
described bath, and then adding about one weight percent water to
the bath followed by boiling the resulting solution for one hour.
~his procedure is repeated with additional water increments of
one weight percent, as shown in the ~able below. The phospha-
tizing coating operation for each bath of varying water content
has been described hereinabove. For each phosphatizing bath,
water con~ent determinations are made prior to phosphatizing by
the above-described method.
TABLE I
Coating Degree of
Bath Water Panel Coatin~ Solubility of
Content,Wt.% Wei~ht: mg~ft Coatinq in Water
0.1 4 60%
l.l 6 50%
2.1 10 20
3.1 13 ~ 5
30 4.1 24 ~5%
-25-
1079164
The tabulated results demonstrate the enhancement in the
degree of water insolubility for the phosphate coating as the
water content in the phosphatizing bath increases. As determined
by visual inspection, it is also noted that the degree of uni-
formity of the phosphate coating is increasing as the water
content of the phosphatizing bath increases. For the particular
syst~m of this Example, the desirable wat~r content is deemed to
be between about 2 weight percent and about 5 weight percent.
Below about 2 weight percent, the degree of water solubility for
the coated panels is regarded as being excsssive. By continuing
the step-wise water addition discussed hereinabove, this system
is found to separate free water, i.e., lose liquid phase homo-
geneity, when the water content reaches 5.1 weight percent.
EXAMPT~ 2
A phoqphatizing solution is prepared from 7510 parts o
methylene chloride, 1731 parts methanol, 5 parts ortho phosphoric
acid, 374 parts N,N-dimethyl formamide, and 7 parts dinitroto-
luene. Prior to phosphatizing of steel panels the water content
of the phosphatizing bath is determined, as described in Example
1, to be 373 parts.
Panels coated in the phosphatizing solution are subjected to
the water solubility test. Such testing shows the panels to have
a degree of solubility in water of below 5%. Coati~g wei~hts for
similar panels, but phosphatized for different coating times,
are determined to be 35 mg/ft2 for one panel (lower coating
weight) ar.d 60 ms/ft2 for another panel (higher coatir.g weisht~.
One of each panel of the lower and the higher coatins weisht
is then selected for analysis by the ~lect-on Spectroscopy for
Chemical Analysis (ESCA~ technique. This tec~nique is used to
ev luate the sur ace phenomena of the coated panels by prov~d-ns
a determination of the elements present. The inst-ument used ls
1079164
the ~P 5950A, a spectrometer system with monochromatized X-
radiation and manufactured by the Hewlett Pac~ard Company. Under
such evaluation, the surface of test panels is found to contain
codium and calcium in trace amounts and a balance of phosphorus,
iron, oxygen, carbon and nitrogen.
Such determination for the principal elements found in the
phosphatized coating is further evaluated, using similar test
panels, with Auger spectroscopy. For this analysis the instru-
ment used is the P~I Model 540A thin film analyzer manufactured
by Physical Electronics Industries, Inc. Such analysis confirms
the presence at the surface of the test panels of the elements
phosphorous, iron, oxygen, car~on and nitrogen.
EXAMPT~ 3
To 380.2 parts of methylene chloride there is added, with
vigorous agitation, 81 parts methanol, 2.3 parts ortho phosphoric
acid, 14.9 parts N,N-dimethyl formamide and 0.4 part dinitro-
toluene. These blended ingredients are thereafter processed in
the manner of Example l to prepare a phosphatizins solution
having a water content of about 0.1 weight percent.
Degreased steel panels are then phosphatized in the compo-
sition. Additional phosphatizing compositions but having dif-
fering water contents, as shown in the Table below, are prepar~d
as described in Example 1. Phosphatizing operation for each bath
of varying water content is also as has been described herein-
before. As shown in the T~ble below, for each phosphatizing
bath, water oor.tent determinations are made prior to phospha-
tizing and coating weights and water solubility testing for
coatings, are determined for a71 phosphatized panels.
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1079164
TABLE II
Coating Degree of
Bath Water Panel Coatin~ Solubility of
Content, Wt.% Weight: mq/ft Coatin~ in Water
-
0.1 9 17%
0.8 9 8
2.1 14 ~ 5%
3.0 22 ,
4.2 31 c5~
The tabulated results demonsl-ate the enhancement in the
degree of water insolubility of the phosphate coating as the
water content in the phosphatizing ~ath increases; also, visual
inspection confir~s that the degree of uniformity of the phos-
phate coating is increasing as the water content of the phospha-
tizing bath increases. Also the coating weight shows a dramatic
increase along with the increase in water content of the coating
bath at a water content level above 2 weight percent. For the
particular system of this Example, t~e desirable water content is
deemed to be between about 2 weight percent and about 5 weight
percen~. Below about 2 weight percent, a desirable coating is
not efficiently achieved. Coating weight i3 very small. By
further water addition to the bath, this system is found to
separate free water, i.e., lose liquid phase homogeneity, when
the water content reaches 5.1 weight percant.
EXAMPLE 4
A standard solution was prepared to contain, by weight, 1188
parts of methylene chloride, 253 parts methanol, 7.3 pa~ts or~ho
phosphoric acid, 60 parts water and l.0 part dinitrotoluene.
These ingredients were blended together with vigorous agitation
and thereafter aliquot portions of this solution were tæken.
These aliquots each contained 118.8 par~s of methylene ch~oride
with additional ingredients thus scalad down respectively. To
each aliquot there was then added an aprotic orsanic com?our.d.
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1079164
The aprotic organic substance for each ali~uot, together
with its proportion in each aliquot, are shown in the Table
below. Baths for phosphatizing were prepared from each aliquot,
steel p&~els were phcsphatized and the phosphatizing operation
was carried on all as has been described hereinbefore. For each
aliquot the water content is shown in the Table below; it was
determi~ed as the proportion of the water for each aliquot de-
rived from the sta~dard solution. Coating weights were deter-
mined by visual observation, noting panel color; from experience
with such technique of noting panel coating weight change with
color change, the figures in the Table have been given, as typical
a constant degree of accuracy of +5 mg/ft2.
TABLE III
Coating
A~rotic Orqanic Substance Bath Water Panel Coating
Substance Amt.Wt.~ Content,Wt.~ Wt.mg/ft2
-
~imethyl Sulfoxide 3.5 3.83 35
Acetonitrile 2.5 3.87 80
Acetone 2.6 3.87 25
20 Nitromethane 3.6 3.83 60
Nitrobenzene 3.8 3.8 55
Tetramethylene
Sulfone 4.2 3.82 35
In all cases, desirable uniform phosphate coatings were no~ed by
visual inspection of coated panels.
EXA~PT~ 5
Solu~ions in the nature of the aliquots of Exampl_ 4 were
prepared to contain, by weight, 118.8 parts o' me~hyler.e chlo-
ride, 4.7 parts N,~-dimethyl formamide, 0.73 pa-t ortho phospho-
ric acid and 0.1 part dinitrotoluene. During the ble~ding oreach solution there was added water plus a sclubilizing solvent.
_~9_
1079164
The solvent for each solution, together with its proportion
in each solution, are shown in the Ta~le below. The proportion
of water in each solution is also shown in the Table below.
Baths for phosphatizing were prepared from each solution in the
manner discussed hereinabove. Steel panels, these panels being
2" x 4" cold rolled, low carbon steel panels, were then phospha-
tized. For each panel the coating weight was determined, as
described in Example 4, and data for this is shown in the Table
below.
TABLE IV
Coating
Organic Solvent Bath Watar Panel Coating
Content, Wt.% Wt.mg/ft2
Etha~ol 17.9 3.77 45
n-Propanol 26.4 3.38 ~0
iso-Propanol 23.4 3.50 40
Allyl Alcohol 34.4 3.02 45
n-Butanol 41.7 2.68 40
sec-Butanol 38.5 2.83 55
tert-Butanol 33.9 3.04 25
n-Pentanol 49.9 2.30 35
In all cases, desirable uniform phosphate coatings were ..oted by
~isual inspection of coated panels, including the ba.h containing
the n-pentanol, in which bath the methylene chloride does not
provide the major amount of the bath compositi~n.
E ~PLE 6
In the manner descri~ed hereinabove, a phosphatizing solutio~
is prepared to contain, by weight, the following ingred ents: 60
parts wat~r, 1188 part~ methylene chloride, 253 parts methanol,
7.3 parts ortho phosphoric acid, 47.2 parts ~ dimethyl formamid~
and 1.0 part dinitrotoluene. Hereinafter, for con~enience, the
resulting phosphatizing solution is referred to as the "new
organic phosphatizing composition"
-30-
1079164
Steel panels were phosphatized in this new organic phos-
phatizing composition. Further, in the manner described herein-
before, but for comparative purposes, panels were phosphatized in
a well-known and extensively-used commercial phosphatizing bath
based on trichloroethylene. Hereinafter for convenience, this
bath is referred to as the "standard organic phosphatizing
composition". This standard organic phosphatizing composition
was prepared by blendins together ortho phosphoric acid, with two
products sold under the trademarks of "Triclene-~" and "Triclene-
R", to contain a commercially acceptable amount of phosphoricacid in the blend. ~he use of such a commercial phosphatizins
bath has been described, for example, in U.S. Patent 3,356,540.
Additional comparative test panels used herein for evalua-
tion are panels phosphatized with an aqueous phosphatizing compo-
sition and prepared in accordance with specifications that are
generally accepted as standards for performance in the automotive
and hcusehold appliance industries. These comparative test
panels, for convenience, are generally referred to herein as
prepared from the "comparative aqueous phosphatizing composition".
Such composition is a solution that can contain zinc acid phos-
phate, with the test panels being dipped in this aqueous solution
typically for one minute. ThereaCter, the test panels are rinsed
and then immersed in a diluts solution of chromic acid. Such
test panels are then dried and are thus provided with a chromic
acid rinse coating.
~ 11 test panels are painted, before testing, with a comme--
cial enamel topcoat. The enamel ls a co~mer~ial white alXyd
baking enamel; the enamel ostensibly contains a ~odified alXyd
resin based upon a system of part ally poiymer zed ~hthallc acid
and glycerin, and has 50 weight percent solids. .~f~er coatins
panels with the enamel, the coating is cured on all panels by
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1079164
baking in a convection oven for 20 minutes at a temperature of
320-325F.
Panels are then selected and subjected to the various tests
described hereinbefore for testing paint film retention and
integrity. The tests used, and the results obtained, are listed
in the Table below. In the conical mandrel test, the numbers
listed in the Tabla are centimeters of paint removal after taping;
the reverse impact test is conducted at 64 inch-pounds. For the
reverse impact test and the conical mandrel test, where a range
is presented in the Table, such range results from the testing of
a series of panels.
In the following Table the efficacy of the total coating
obtained on the coated parts in the cross hatch and reverse
impact tests is quantative y evaluated on a numerical scale from
0 to 10. The parts are visually inspected and compared with one
another and the system is used for convenience in the reviewing
of results. In the rating system the following numbers are used
to cover the following resu}ts:
(10) complete retention of film, exceptionally
good for the test used;
(8) some initial coating degradation;
~6) moderate loss of film integrity;
(4) significant film loss, unacceptable degradation
of film integrity;
(2) some coating re~ention only;
(0) complete film loss.
-32-
1079164
TABLE V
Phosphatizing Cross Conical Reverse Coin
Composition ~atch Mandrel Impact Adhesion
New Organic 10 0-1.7 6-9 Good
Phosphatizing
Composition
Sta~dard Organic 10 0.4-1.9 4-8 Good
Phosphatizing
Composition
Comparative Aqueous 10 1.9 4-9 Good
Phosphatizing
Compo~itio~
The above-tabulated results show that the phosphate coating from
the new organic phosphatizing composition can provide paint
adhesion that will compare under a variety of tests as the equal
of or superior to, comparative systems based either on organic
commercial baths or aqueous compositions.
In further and related testing, panels from the new orga~ic
phosphatizing composition are provided with a chrome rinse from a
dilute chromic acid solution. This i9 done to equate the nature
of the coating on the panels with that from the aqueous phospha-
tizing composition. All test panels are topcoated witA an al~yd
enamel paint system and then panels are subjected to a variety of
tests. Comparable results, for each specific test, are obtained
among all tested panels. Such equality of test results is
achieved even when testing of comparative panels in the standard
salt spray (fog) test, AST~ B-117-64.
EXAMPLE 7
To 356.4 parts of methylene chloride there is added, with
vigorous a5itation, 106.6 parts ethanol, 2.4 parts ortho phos-
phoric acid and 15.3 parts ~,N-dimethylformamide. These blended
ingredients are thereafter processed in the manner of Example 1
to prepare a phosphatizing solution having a water content of
about 0.1 weight percent.
1079164
Degreased steel panels are then phosphatized in the compo-
sition. Additional phosphatizing compositions, but having dif-
fering water contents, as shown in the Table below, are prepared
as described in Example 1. Phosphatizing operation for each bath
of varying water content is also as has been described herein-
before. As shown in the Ta~le below, for each phosphatizing
bath, coating weights and water solubility testing for coatings,
are determined for phosphatized panels.
TABLE VI
10Coating De~ree of
Bath Water Panel Coating Solubility of
Content, Wt.~Weiqht; mg/ftZ C02tinq in Water
0.1 14 28%
1.1 lO 303
2.1 22 7%
3.1 27 ~5%
4.1 125 ~5%
The tabulated results demonstrate the enhancement in the
degree of water insolubility of the phosphate coating as the
water content in the phosphatizing bath increases; also, ~isual
Lnspection confirms that the degree of uniformity of the phos-
phate coating is increasing as the water content of the phos-
phatizin~ bath increases. Also, after an initial reversal, the
coating weight increases right along with the increase in water
content of the coating bath. For the particular system of this
Example, the desirable water content is Zeemed to be greater than
2.1 weight percent and up to about 5 weight percent. By further
water addition to the bath, this system is 'ound to sepzrate 'ree
water, i.e., lose li~uid phase homogeneity, when the water con-
tent reaches 5.1 weight percent.
For comparative p~r~oses, the "s~&ndard organic ?hos?ha-
tizing composition" described in Example 6 is used to coat
panels and the panels are tested. This composit~`on, ~ased on
1079164
trichlorethylene, has met with commercial acceptance as a solvent
phosphatizing composition. When the composition contains 0.2
weight percent water, all water determinations being by the
method described in Example 1, the composition provides for a
very uniform coating of desirable weight. All panel coating is
conducted as has been described hereinbefore.
The 0.2 weight percent water content, although not typical
for such a commercial bath, can be presented and contributed hy
the other substituents in the bath, as for example, when the acid
is pro~ided in the orthophosphoric form. A test panel from this
bath, in water solu~ility testing, exhibits a degree of water
solu~ility of 60%. A duplicate bath, except that it is in
equilibrium with 0.5 weight percent water, supplied by water
addition, also yields uniform coati~gs of desirable weight.
At the 0.5 weight percent level, the coating has a deqree of
water solubility of 28%. This approaches the minimum degree for
coatings from such bath, since up~n further water addition, the
bath is found to lose homogeneity at only 0.6 weight percent
water.
EXAMPLE 8
A standard solution was prepared to contain, by volume, 900
parts of methylene chloride, 320 parts methanol, 50 parts N,N-
dimethylformamide, 4 5 parts ortho phosphoric acid and 60 parts
water. These ingredients were blended togethe~ with vigorous
agitation and thereafter ali~uot porticns of ~his solution were
taken. These ali~uots each conta~ned 90 parts of methylene
chloride with additional ingredier.ts thus scaled down respec-
tively. To each aliquot there was then added 0.064 weight
percent of organic accelerator compound, with the exception of
one aliouot that was kept free from accelerator compo~nd for
comparative purposes.
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The particular organic accelerator substance for each
aliquot is shown in the Table below. Baths for phosphatizing
were prepared from each aliquot, steel panels were phosphatized
and the phosphatizing operation was c-~rried on all as has been
described hereinbefore, with all panels being coated for an equal
time. Coatins weights were determined as described hereinbefore
and are shown in the Table below. Relative coating weights for
coatings from each aliquot, basis a given weight of 1.00 for the
coating weight from the aliquot that was maintained free from
accelerator compound, are also shown in the Table.
TABLE VII
Panel Coating ~elative Panel
Organic Accelerator Substance Wt.mg/ft2 Coatinq Weiqht
None 45 1.00
Ethylenediaminetetraacetic acid* 48 1.07
Dinitrotoluene 55 1.22
Dlmethyl Isobutylene Amine 56 1.24
Dimethyl Sulfoxide 62 1.38
Thiourea 63 1.40
Pyridine 71 1.58
Urea 78 1.73
*Disodium salt.
In all cases, desirable phosphate coatings were noted.
EXAMoer~ g
A phosphatizing bath is prepared in the manner of Example
1 to contain, on a basis of 100 parts of prepared bat~: 46.47
parts methylene chloride, 48.96 parts 2-butoxyethanol, 2.34 par_s
water, 1.84 part N,N-dimethylformamide, 0.3S part phosphoric acid
and 0.04 part dinitrototuene. Steel test panels are then ?nos-
~hatized and are thereafter subjected to visual inspection orinterpretation of coating results. By such inspection the ?hos-
phatized panels are viewed to ha~e a desirably uni~orm coat n5 of
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sufficient weight deemed to be acceptable for commercial purposes.
This result is achieved with the 2-butoxyethanol being present as
the organic solvent and with the methylene chloride not being
present in major amount.
EXAMPLE 10
A composition for sustaining phosphatizing by addition to a
depleted phosphatizing ~ath is prepared by blending together
93.28 parts methylene chloride, S.99 parts methanol, 0.71 part
water, O.01 part p-tertiaryamyl phenol and O.01 part p-benzo-
quinone. ~ereinafter, the resulting homogeneous, stable solutionis referred to as the "bath-sustaining solutionn.
There is separately prepared, by blendi~g together into a
homogeneous solution, 62.75 parts methanol, 17.57 parts water,
19.13 parts N,~-dimethylformamide, 0.38 part dinitrotoluene, 0.12
part p-tertiaryamyl phenol, and 0.044 part p-benzoquinone. One
part by volume of this resulting uniform solution is then blended
with three partq by volume of the bath-sustaining solution. To
this resulting homogeneous blend there is then added sufficient
orthophosphoric acid to provide about 0.22~, by volume, of the
orthophosphoric acid in the resulting blend.
The phosphatizing bath thereby prepared is subsequently used
to phosphatize degreased 3" X 4" steel panels. These phospha-
tized panels are referred to hereinafter as the ~initially-
phosphatized panels~. Following this initial working of the
bath, the bath is subjected to heat-induced vapor loss. ~rom the
working and the subsequent vapor loss, t~e bath experiences about
a 31% loss, by volume. This is deemed io be a loss that wou'd
otherwise be observed following very frequent, ex.ended us~ o'
the bath as a phosphatizing bath.
After this contraction in the bath, additional panels, being
degreased 3" X 3" steel panels for reconciliation with the volume
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of the bath, are coated. These coated panels are referred to
hereinafter as the "depleted bath panels".
The resulting depleted bath is then permitted to cool, and
the cool bath ls rest^red to its original volume by adding the
bath-sustaining solution. After addition, ~e bath is then
heated, as described in Example 1, and additional 3" X 4 n steel
panels are coated. Resulting coated panels are referred to as
the n restored bath panels~.
The ~uality of the coating on the panels, from both the new
10 bath panels and the restored bath panels, is deemed to be of a
quality acceptable for commercial purposes. Such qulity is
judged by visual inspection of coating uniformity as well as
determination of coating weight, which determination is conducted
as has been described hereinbefore. On the other hand, the
depleted bath panels c~n ~e seen from visual inspection to have
non-uniform coatings that are judged to be commer~ially unaccept-
able. Thu~, the worked bath of contracted volume that provides
commercially unacceptable panels, can be successfully rejuvenated
with the bath-sustaining solution, as is e~idenced by coatings
20 achieved on resulting coated panels.
EXAMpT,~ 11
To 82.5 parts of methylene chloride there is added, with
vigorous agitation, 17.0 parts methanol and 0.5 part ortho phos-
phoric acid. The resulting phosphatizing solution has a water
content of about 0.1 weight percent, at least principally contri-
buted by the acid. A degreased steel panel is then ?hosphatized
in the composition. Additional phosphatizing compositions, but
having differing water contents, are prepared as descri~ed n
Example 1, and panels are phosphatized in such compcs-tions. ~11
30 phosphatizins operations are as have ~een described herei.~be.or~.
Coating weights and water solubiiity testing 'or coatinss, are
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determined for selected phosphatized panels. As t.~e bath water
content goes from 3% to 4%, the coating weight goes from 20 to 9
mg/ft2 respectively. However, with a bath at the 3.2 percent
water level, the most desirable coating, at a weight of about 35
mg/ft2 and having less than 5% water solubility, is achieved.
This result is obtained although the bath contains no aprotic
polar organic compound.
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