U.S. patent application number 11/749906 was filed with the patent office on 2008-11-20 for rinse conditioner bath for treating a substrate and associated method.
Invention is credited to Jeffrey Allen Greene, Mark W. Simpson, Michel Sudour, Donald R. Vonk.
Application Number | 20080283152 11/749906 |
Document ID | / |
Family ID | 39587034 |
Filed Date | 2008-11-20 |
United States Patent
Application |
20080283152 |
Kind Code |
A1 |
Greene; Jeffrey Allen ; et
al. |
November 20, 2008 |
RINSE CONDITIONER BATH FOR TREATING A SUBSTRATE AND ASSOCIATED
METHOD
Abstract
A rinse conditioner bath that comprises a Jernstedt salt and a
soluble iron is disclosed. A method for treating a substrate with
the disclosed rinse conditioner bath as well as a zinc phosphate
solution is also disclosed.
Inventors: |
Greene; Jeffrey Allen;
(Sterling, MI) ; Vonk; Donald R.; (Clinton
Township, MI) ; Sudour; Michel; (Sebourg, FR)
; Simpson; Mark W.; (Warren, MI) |
Correspondence
Address: |
PPG INDUSTRIES INC;INTELLECTUAL PROPERTY DEPT
ONE PPG PLACE
PITTSBURGH
PA
15272
US
|
Family ID: |
39587034 |
Appl. No.: |
11/749906 |
Filed: |
May 17, 2007 |
Current U.S.
Class: |
148/22 ;
148/254 |
Current CPC
Class: |
C23C 22/80 20130101 |
Class at
Publication: |
148/22 ;
148/254 |
International
Class: |
C23C 22/78 20060101
C23C022/78; C23C 30/00 20060101 C23C030/00 |
Claims
1. A rinse conditioner bath comprising a Jernstedt salt and a
soluble iron.
2. The rinse conditioner bath according to claim 1, wherein said
soluble iron is iron (II).
3. The rinse conditioner bath according to claim 1, wherein said
iron comprises 5-1000 ppm of the total weight of said rinse
conditioner bath.
4. The rinse conditioner bath according to claim 3, wherein said
iron comprises 20-30 ppm of the total weight of said rinse
conditioner bath.
5. The rinse conditioner bath according to claim 1, wherein said
soluble iron is introduced into said rinse conditioner bath via a
salt.
6. The rinse conditioner bath according to claim 1, wherein said
salt is in solid or aqueous form.
7. The rinse conditioner bath according to claim 5, wherein said
salt comprises ferrous nitrate, ferrous sulfate, ferrous chloride,
ferrous gluconate, or combinations thereof.
8. The rinse conditioner bath according to claim 1, wherein said
rinse conditioner bath is prepared from a mixture of a rinse
conditioner concentrate and an aqueous medium.
9. The rinse conditioner bath according to claim 8, wherein said
rinse conditioner concentrate is an aqueous rinse conditioner
concentrate containing said soluble iron.
10. The rinse conditioner bath according to claim 8, wherein said
rinse conditioner concentrate is a powder concentrate and wherein
said powder concentrate contains said soluble iron.
11. The rinse conditioner bath according to claim 1, wherein said
rinse conditioner bath further comprises chelating compounds.
12. The rinse conditioner bath according to claim 1, wherein said
soluble iron is a reaction product of iron (III) and a reducing
agent.
13. A method for treating a substrate comprising (a) applying a
rinse conditioner bath comprising a Jernstedt salt and a soluble
iron to at least a portion of said substrate, and (b) phosphatizing
at least a portion of said portion of said substrate with a zinc
phosphate solution.
14. The method according to claim 13, wherein said soluble iron is
iron (II).
15. The method according to claim 13, wherein said iron comprises
5-1000 ppm of the total weight of said rinse conditioner bath.
16. The method according to claim 15, wherein said iron comprises
20-30 ppm of the total weight of said rinse conditioner bath.
17. The method according to claim 13, further comprising
introducing said soluble iron into said rinse conditioner bath via
a salt.
18. The method according to claim 17, wherein said salt comprises
ferrous nitrate, ferrous sulfate, ferrous chloride, ferrous
gluconate, or combinations thereof.
19. The method according to claim 17, wherein said salt is in solid
form.
20. The method according to claim 17, wherein said salt is in an
aqueous medium.
21. The method according to claim 13, wherein said rinse
conditioner bath is prepared by (i) providing an aqueous solution
and (ii) introducing an aqueous rinse conditioner concentrate
comprising said Jernstedt salt and said soluble iron into said
aqueous solution.
22. The method according to claim 21, wherein said aqueous rinse
conditioner concentrate comprises a liquid thickener, a chelating
compound, and said Jernstedt salt.
23. The method according to claim 13, wherein said rinse
conditioner bath is prepared by (i) providing an aqueous solution,
(ii) introducing a powder concentrate comprising said Jernstedt
salt into said aqueous solution, and (iii) introducing said soluble
iron into said aqueous solution.
24. The method according to claim 13, wherein said rinse
conditioner bath is prepared by (i) providing an aqueous solution,
(ii) forming a powdered mixture comprising said soluble iron and
said Jernstedt salt, and (iii) introducing said powdered mixture
into said aqueous solution.
25. The method according to claim 13, wherein said rinse
conditioner bath further comprises chelating compounds.
26. The method according to claim 13, wherein said soluble iron is
a reaction product of iron (III) and a reducing agent.
27. A rinse conditioner concentrate comprising a Jernstedt salt and
another salt, wherein said another salt comprises a soluble
iron.
28. The rinse conditioner concentrate according to claim 28,
wherein said another salt is in aqueous or solid form.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a rinse conditioner bath
comprising a Jernstedt salt and a soluble iron and a method for
using the same.
[0003] 2. Background Information
[0004] Phosphate conversion coatings are well known for treating
metal surfaces, particularly ferrous, zinc and aluminum metals and
their alloys. When applied, these phosphate coatings form a
phosphate layer, primarily of zinc and iron phosphate crystals,
which provides corrosion resistance and/or enhances the adhesion of
subsequently applied coatings.
[0005] Prior to application of the phosphate coating, the metal
substrate is typically "conditioned" or "activated" by subjecting
the surface of the metal substrate to a diluted aqueous dispersion,
sometimes referred to as a rinse conditioner bath or activator, by
introducing or immersing the metal substrate into a tank that
contains the rinse conditioner bath. "Activation" of the surface of
the metal substrate is achieved due to the adsorption of colloidal
titanium-phosphate particles, which are present in the rinse
conditioner bath, to the metal's surface. These colloidal
titanium-phosphate particles, however, have a tendency to
agglomerate in the rinse conditioner bath due to dissolved calcium
(Ca.sup.2+) and magnesium (Mg.sup.2+) ions (hard water ions) that
are typically present in the rinse conditioner bath. The hard water
ions are usually introduced into the rinse conditioner bath via the
water that is used to create the rinse conditioner bath.
Accordingly, to prevent agglomeration of the colloidal
titanium-phosphate particles, chelating or sequestering compounds,
such as polyphosphates and pyrophosphates, are introduced into the
rinse conditioner bath. These chelating/sequestering compounds,
however, have been found to degrade with time and cause premature
failure of the rinse conditioner bath since the chelating compounds
lose their ability to sequester the hard water ions. If softened
water is used to create the rinse conditioner bath, these chelants
can attack the Jernstedt salt itself and cause the dissolution of
the colloidal titanium-phosphate particles thereby preventing the
"activation" of the surface of the metal substrate. A rinse
conditioner bath having an extended "life span" is therefore
desired.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to a rinse conditioner
bath comprising a Jernstedt salt and a soluble iron.
[0007] The present invention is also directed to a method for
treating a substrate comprising applying a rinse conditioner bath
comprising a Jernstedt salt and a soluble iron to at least a
portion of the substrate, and phosphatizing at least a portion of
the substrate with an aqueous zinc phosphate solution.
[0008] The present invention is further directed to a rinse
conditioner concentrate comprising a Jernstedt salt and another
salt, wherein the another salt comprises a soluble iron.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A full understanding of the invention can be gained from the
following description of the preferred embodiments when read in
conjunction with the accompanying drawings in which:
[0010] FIG. 1 is a top elevation view of a surface of a cold-rolled
steel panel under a scanning electron microscope at 1000.times.
after the cold-rolled steel panel has been phosphatized with a zinc
phosphate solution;
[0011] FIG. 2 is a top elevation view of a surface of another
cold-rolled steel panel under a scanning electron microscope at
1000.times. after the cold-rolled steel panel has been phosphatized
with a zinc phosphate solution;
[0012] FIG. 3 is a top elevation view of a surface of yet another
cold-rolled steel panel under a scanning electron microscope at
1000.times. after the cold-rolled steel panel has been phosphatized
with a zinc phosphate solution; and
[0013] FIG. 4 is a top elevation view of a surface of yet another
cold-rolled steel panel under a scanning electron microscope at
1000.times. after the cold-rolled steel panel has been phosphatized
with a zinc phosphate solution.
DETAILED DESCRIPTION OF THE INVENTION
[0014] As used herein, unless otherwise expressly specified, all
numbers such as those expressing values, ranges, amounts or
percentages may be read as if prefaced by the word "about", even if
the term does not expressly appear. It is also understood that a
plural term can encompass its singular counterpart and vice
versa.
[0015] When referring to any numerical range of values, such ranges
are understood to include each and every number and/or fraction
between the stated range minimum and maximum.
[0016] As used herein, the phrase "rinse conditioner bath" will
refer to an aqueous solution and/or a colloidal suspension that is
applied onto at least a portion of a substrate and/or into which at
least a portion of a substrate is immersed in order to promote the
formation of a zinc phosphate coating on at least a portion of the
substrate that was treated with the rinse conditioner bath. It is,
therefore, understood that the substrate is treated with the rinse
conditioner bath prior to phosphatizing at least a portion of the
treated substrate with a zinc phosphate solution.
[0017] As used herein, the phrase "soluble iron" refers to an iron
compound that is soluble in an aqueous medium such as water or a
solvent. For example, in one embodiment, the "soluble iron" is
ferrous iron (i.e., Fe.sup.2+) that is formed by dissociation of a
salt in an aqueous medium. In another embodiment, the "soluble
iron" is ferrous iron that is a reaction product of ferric iron
(i.e., Fe.sup.3+, Fe(III)) and a reducing agent such as, without
limitation, hydrogen peroxide (H.sub.2O.sub.2), which is produced
in situ.
[0018] As used herein, the term "vehicle" or variations thereof
includes, but is not limited, to civilian, commercial, and military
land vehicles such as cars and trucks.
[0019] The present invention is directed to a rinse conditioner
bath that is utilized to "activate" or "condition" at least a
portion of a substrate prior to phosphatizing at least a portion of
a substrate with a zinc phosphate solution. In other words, the
rinse conditioner bath promotes the formation of zinc and zinc/iron
phosphate crystals on the substrate when at least a portion of the
substrate, which was subjected to the rinse conditioner bath, is
phosphatized with a zinc phosphate solution. Non-limiting examples
of a suitable substrate that can be treated with the rinse
conditioner include, but are not limited to, a metal and/or a metal
alloy. For example, the metal and/or metal alloy can be aluminum,
steel, or zinc. In one embodiment, a steel substrate could include
cold rolled steel, electrogalvanized steel, and hot dipped
galvanized steel. In one embodiment, the substrate may comprise a
portion of a vehicle such as a vehicular body (e.g., without
limitation, door, body panel, trunk deck lid, roof panel, hood,
and/or roof) and/or a vehicular frame.
[0020] The rinse conditioner bath is comprised of a Jernstedt salt
and a soluble iron. The Jernstedt salt typically comprises
titanium-phosphate particles such as colloidal titanium-phosphate
particles. In one embodiment, the Jernstedt salt is
Na.sub.4TiO(PO.sub.4).sub.2. As will be discussed in greater detail
below, the addition of soluble iron to the rinse conditioner bath
dramatically increases the "life span" of the rinse conditioner
bath. As used herein, the phrase "life span" will refer to the
total amount of time (e.g., hours, days, weeks, months, etc. . . .
) that the rinse conditioner bath is capable of promoting the
formation of zinc phosphate on a substrate. Accordingly, it will be
understood that an increase in the "life span" of the rinse
conditioner bath will mean that the rinse conditioner bath will not
have to be replaced as often, when compared to a rinse conditioner
bath that lacks soluble iron, since the rinse conditioner bath
disclosed in this invention is capable of promoting the formation
of zinc phosphate on the substrate over an extended period of
time.
[0021] In one embodiment, the soluble iron is introduced into a
rinse conditioner bath via a salt such as, without limitation,
ferrous nitrate, ferrous sulfate, ferrous chloride, ferrous
gluconate, or combinations thereof. The salt can either be in solid
form (e.g. powder/particulate form) or in aqueous form (i.e.,
dissociated ions in an aqueous medium). In another embodiment, an
aqueous rinse conditioner concentrate, which comprises the salt in
aqueous form, a liquid thickener, chelating compound(s), and a
Jernstedt salt, is added to an aqueous solution, such as water, to
form the disclosed rinse conditioner bath. Suitable liquid
thickeners that can be used in the aqueous rinse conditioner
concentrate would include, but are not limited to, hydroxyl methyl
cellulose, xanthan gum, and polycarboxylic acid, and combinations
thereof. In yet another embodiment, the rinse conditioner is formed
by the introduction of a powder concentrate, which comprises a
chelating compound, into an aqueous solution, such as water, to
form a precursor to the rinse conditioner bath. The salt, which is
in aqueous and/or solid form, is then added to the precursor to the
rinse conditioner bath in order to form the disclosed rinse
conditioner bath. In yet another embodiment, the salt, which is in
solid form, is added to a powder concentrate before the powder
concentrate is added to the aqueous solution to form the disclosed
rinse conditioner. Hereinafter, the aqueous rinse conditioner
concentrate as well as the powder concentrate will be collectively
referred to as a rinse conditioner concentrate. It will be
understood that, as used herein, the rinse conditioner concentrate
is typically used to make the rinse conditioner bath that is
applied onto a substrate prior to the substrate being subjected to
a phosphatizing step using a zinc phosphate solution.
[0022] In the various embodiments described above, the aqueous
solution to which the rinse conditioner concentrate is added could
be an aqueous solution which has low hardness. As used herein, the
phrase "low hardness" refers to an aqueous solution containing
.ltoreq.25 ppm of calcium carbonate and/or magnesium. For example,
the aqueous solution could be deionized water, distilled water,
reverse osmosis water, or combinations thereof.
[0023] The soluble iron can be present in the rinse conditioner
bath in an amount ranging from 5 to 1000 ppm based on the total
weight of the rinse conditioner bath. In another embodiment, the
soluble iron can be present in the rinse conditioner bath in an
amount ranging from 20 to 30 ppm based on the total weight of the
rinse conditioner bath. As demonstrated in the examples below,
addition of soluble iron into the rinse conditioner bath can
increase the "life span" of the rinse conditioner bath. Though not
wishing to be bound by any particular theory, it is believed that
the addition of soluble iron into the rinse conditioner bath
extends the "life span" of the rinse conditioner bath because the
chelating/sequestering compounds, which are typically added to the
rinse conditioner bath, have a preference to attack the soluble
iron as opposed to attacking and causing the dissolution of the
Jernstedt salt. Because the Jernstedt salt is not dissolved by the
chelating/sequestering compounds, the Jernstedt salt would continue
to promote the formation of zinc and iron phosphate crystals on the
substrate that is being treated.
[0024] In one embodiment, the rinse conditioner bath to which the
soluble iron is added comprises sodium phosphate, potassium
phosphate, and titanium wherein the titanium is present as a
complex salt with either or both sodium phosphate and the potassium
phosphate.
[0025] Suitable sodium phosphates useful in the rinse conditioner
bath described in the preceding paragraph include, without
limitation, mono- di- or tri-sodium phosphate, pentasodium
triphosphate (also known as sodium tripolyphosphate), tetrasodium
diphosphate, (tetrasodium pyrophosphate) disodium orthophosphate,
pentasodium triphosphate, or combinations thereof.
[0026] Suitable potassium phosphates useful in the rinse
conditioner bath include, without limitation, mono-, di- or
tri-potassium phosphate, pentapotassium triphosphate (also known as
potassium tripolyphosphate), dipotassium orthophosphate,
tetrapotassium pyrophosphate or combinations thereof.
[0027] A variety of titanium (IV) compounds or salts may be used as
the source of titanium in the rinse conditioner bath as long as the
anion of the salt does not interfere with the subsequent zinc
phosphate pretreatment. For example, titanium halides, titanium
oxides (e.g., titanium dioxide), titanium sulfates and titanium
oxalates may be used. While the selection of the titanium source is
not limited, titanium halides, specifically potassium titanium
fluoride is most suitable.
[0028] The rinse conditioner bath may further comprise additional
optional components such as, without limitation, diphosphonic
acids, alkali metal carbonates or hydroxides and/or thickening
agents (e.g., xanthans, polysaccharides and polycarboxylates).
[0029] The rinse conditioner bath described above can be prepared
by introducing a rinse conditioner concentrate to an aqueous medium
such as water. In one embodiment, the rinse conditioner concentrate
is prepared by mixing in an aqueous medium a sodium phosphate with
a titanium compound and heating the mixture to form a paste-like
pre-mix. For example, the paste-like premix can be made by adding
pentasodium triphosphate to water, which is preheated to a
temperature ranging from 65.degree. C. to 95.degree. C., in order
to form a slurry. A titanium compound is then added to the slurry
and the slurry is agitated. After thorough mixing, disodium
orthophosphate is added to the slurry and the slurry mixed
thoroughly for about 5 to 15 minutes. After the disodium
orthophosphate is mixed with the slurry, a paste-like pre-mix
containing the titanium phosphate complex salt is produced.
[0030] The paste-like pre-mix is then combined with potassium
phosphate and other ingredients, such as a liquid thickener, to
form the conditioner concentrate. The potassium phosphate may be
one or a combination of the potassium phosphates described above.
It is generally suitable to use dipotassium orthophosphate or a
combination of dipotassium orthophosphate and pentapotassium
triphosphate. tetrapotassium pyrophosphate is additionally suitable
when activating aluminum substrates. It is noted that in other
embodiment, the paste-like pre-mix may be added to the potassium
phosphate hot or after a cooling period. In this particular
embodiment, the rinse conditioner concentrate is a concentrated
aqueous dispersion of a titanium containing phosphate
composition.
[0031] Typically, the sodium phosphate is present in amounts of
from 10% to 30% by weight, the potassium phosphate is present in
amounts of from 20% to 40% by weight, the titanium is present in
amounts of from 0.05% to 2.5% by weight, and water is present in
amounts of from 30% to 60% by weight, the percentage by weight
based on the total weight of the ingredients used in making the
rinse conditioner concentrate. Usually, the sodium phosphate is
disodium orthophosphate in combination with pentasodium
triphosphate, and the disodium orthophosphate is present in amounts
of from 10% to 25% by weight and the pentasodium triphosphate is
present in amounts of from 1% to 10% by weight, the percentage by
weight being based on total weight of ingredients used in making
the rinse conditioner concentrate. The potassium phosphate is
preferably dipotassium orthophosphate in combination with
pentapotassium triphosphate, and the dipotassium orthophosphate is
typically present in amounts of from 5% to 20% by weight and the
pentapotassium triphosphate is present in amounts of from 10% to
25% by weight, the percentage by weight being based on total weight
of ingredients used in making the rinse conditioner concentrate. In
the embodiment where tetrapotassium pyrophosphate is used, the
tetrapotassium pyrophosphate is present in amounts of up to 5% by
weight based on total weight of the ingredients used in the making
of the rinse conditioner concentrate.
[0032] In accordance with a method of the present invention, a
substrate is treated by (a) applying a rinse conditioner bath
comprising a Jernstedt salt and a soluble iron to a least a portion
of the substrate, and (b) phosphatizing at least a portion the
substrate with an aqueous zinc phosphate solution. In one
embodiment, the rinse conditioner bath can be applied to the
substrate by spray, roll-coating or immersion techniques. The rinse
conditioner bath is typically applied onto the substrate at a
temperature ranging from 20.degree. C. to 50.degree. C. for any
suitable period of time. After the surface of the substrate has
been "activated", the surface of the substrate is subjected to a
phosphate pretreatment such as a zinc phosphate pretreatment. The
phosphatizing step can be performed by spray application or
immersion of the activated substrate in an acidic phosphate bath
which contains zinc and other divalent metals known in the art at a
temperature ranging from 35.degree. C. to 75.degree. C. for 1 to 3
minutes. After phosphatizing, the substrate is optionally
post-rinsed with a chromium or non-chromium containing solution,
rinsed with water and optionally dried. Paint is then typically
applied, such as, by electrodeposition or by conventional spray or
roll coating techniques.
[0033] The present invention is also directed to a conditioner
stage such as those used in an automotive manufacturing facility.
In one embodiment, the conditioner stage comprises an immersion
tank which contains the rinse conditioner bath that is disclosed in
this invention. In one embodiment, the rinse conditioner bath is
contained within the immersion tank at a temperature ranging from
20.degree. C. to 50.degree. C. A portion of the substrate is
subjected to the rinse conditioner bath by immersing the substrate
in the rinse conditioner bath for any suitable period of time.
After being immersed in the rinse conditioner bath, a portion of
the "activated" substrate is then subjected to a phosphatizing step
by applying a zinc phosphate solution to the "activated" substrate.
It should be noted, however, that prior to the application of the
phosphate solution to the "activated" substrate, additional rinse
conditioner bath can be sprayed onto a portion of the "activated"
substrate via a spraying nozzle as the "activated" substrate is
removed from the immersion tank. For example, the spraying nozzle
could be an "exit halo" which is positioned downstream from the
immersion tank. After the "activated" substrate exits the immersion
tank and/or after additional rinse conditioner is applied onto the
"activated" substrate, the "activated" substrate is phosphatized by
applying a zinc phosphate solution to the "activated" substrate
using techniques that are known in the art such as a spray and/or
an immersion technique.
[0034] In another embodiment, the conditioner stage comprises a
number of spraying nozzles that are used to apply the rinse
conditioner bath onto a least a portion of a substrate. Disposed
beneath the spraying nozzles is a spray tank which is adapted to
collect the rinse conditioner bath that exits the spraying nozzles
and/or any excess rinse conditioner bath that drips off the surface
of the "activated" substrate. The spray tank is connected to the
spraying nozzles in a manner that allows the spraying nozzles to
utilize the rinse conditioner bath that is collected in the spray
tank thereby recycling the rinse conditioner bath. After the rinse
conditioner bath is applied onto at least a portion of the
substrate, the "activated" substrate is then phosphatized as
described in the preceding paragraph.
[0035] Whereas particular embodiments of this invention have been
described above for purposes of illustration, it will be evident to
those skilled in the art that numerous variations of the details of
the present invention may be made without departing from the
invention as defined in the appended claims.
EXAMPLES
Example 1
[0036] Two 4 liter rinse conditioner baths, Baths A and B, were
prepared by adding 1.0 gram of a commercially available Liquid
Rinse Conditioner (available from PPG Industries, Inc. of
Pittsburgh, Pa.) per 1 liter of deionized water. No ferrous iron
(Fe(II)) was added to Bath A while ferrous iron was added to Bath B
at a concentration of 20 ppm (0.4 g FeSo.sub.4.7H.sub.20). It will
be understood that Bath A is the control.
[0037] Two cold-rolled steel test panels (available from ACT
Laboratories, of Hillsdale, Mich.), Steel Panels D and E, were
processed through an alkaline cleaning process and rinsed with tap
water. After being rinsed with tap water, Steel Panel D was
immersed in Bath A for 30 seconds at ambient temperature. Steel
Panel D was then removed from Bath A and phosphatized with a zinc
phosphate solution, CHEMFOS 700AL (available from PPG Industries,
Inc. of Pittsburgh, Pa.), which was maintained at a Free Acid (FA)
range of 0.8 to 0.9, a Total Acid (TA) range of 15 to 16.5, and a
temperature of 52.degree. C. (+/-1.degree. C.). After being rinsed
with tap water, Steel Panel E was immersed in Bath B for 30 seconds
at ambient temperature. Steel Panel E was then removed from Bath B
and phosphatized with a zinc phosphate solution, CHEMFOS 700AL,
which was maintained at a Free Acid (FA) range of 0.8 to 0.9, a
Total Acid (TA) range of 15 to 16.5, and a temperature of
52.degree. C. (+/-1.degree. C.).
[0038] Referring to FIG. 1, this is a top elevation view of the
surface 2 of Steel Panel D after Steel Panel D was phosphatized
with CHEMFOS 700AL. The extensive number of nodular crystalline
structures 4 seen in FIG. 1 is the zinc phosphate coating 6 that
was formed over essentially the entire surface 2 of Steel Panel D
during the phosphatizing process. The formation of the
substantially uniform zinc phosphate coating on the surface of
Steel Panel D was promoted by the rinse conditioner bath of Bath A.
Accordingly, the rinse conditioner bath of Bath A was active. As
used hereinafter in connection with the phrase "rinse conditioner
bath", the term "active" will refer to a rinse conditioner bath's
ability to promote the formation a zinc phosphate coating on a
substrate.
[0039] Referring to FIG. 2, this is a top elevation view of the
surface 8 of Steel Panel E after Steel Panel E was phosphatized
with CHEMFOS 700AL. Similar to the zinc phosphate coating that is
seen in FIG. 1, the extensive number of nodular crystalline
structures 10 seen in this figure is a substantially uniform zinc
phosphate coating 12 that was formed over essentially the entire
surface 8 of Steel Panel E during the phosphatizing process. The
formation of the extensive zinc phosphate coating 12 on the surface
8 of Steel Panel E was promoted by the rinse conditioner bath of
Bath B. In other words, the rinse conditioner in Bath B, like Bath
A, was active.
Example 2
[0040] In order to determine the life span of the rinse conditioner
in Baths A and B, two cold-rolled steel test panels, Steel Panels Y
and Z, were immersed in Baths A and B after a 24 hour period from
when Steel Panels D and E were immersed in Baths A and B. Similar
to Steel Panels D and E, Steel Panels Y and Z were processed
through an alkaline cleaning process and rinsed with tap water.
After being rinsed with tap water, Steel Panel Y was immersed in
Bath A for 30 seconds at ambient temperature. Steel Panel Y was
then removed from Bath A and phosphatized with a zinc phosphate
solution, CHEMFOS 700AL, which was maintained at a Free Acid (FA)
range of 0.8 to 0.9, a Total Acid (TA) range of 15 to 16.5, and a
temperature of 52.degree. C. (+/-1.degree. C.). After being rinsed
with tap water, Steel Panel Z was immersed in Bath B for 30 seconds
at ambient temperature. Steel Panel Z was then removed from Bath B
and phosphatized with a zinc phosphate solution, CHEMFOS 700AL,
which was maintained at a Free Acid (FA) range of 0.8 to 0.9, a
Total Acid (TA) range of 15 to 16.5, and a temperature of
52.degree. C. (+/-1.degree. C.).
[0041] Referring to FIG. 3, this is a top elevation view of the
surface 14 of Steel Panel Y after Steel Panel Y was phosphatized
with CHEMFOS 700AL. Unlike, FIGS. 1 and 2, however, the surface 14
of Steel Panel Y lacked the extensive number of crystalline
structures 4, 10 that were observed on the surface of Steel Panels
D and E, respectively. Rather, a few scattered crystalline
structures 16 were observed on the surface 14 of Steel Panel Y.
Moreover, the surface 14 of Steel Panel Y was actually visible when
viewed under the scanning electron microscope. It will be
understood that the rinse conditioner bath of Bath A, after 24
hours, was unable to promote the formation of a substantially
uniform zinc phosphate coating on the surface of Steel Panel Y. In
other words, the life span of the rinse conditioner bath of Bath A
was essentially 24 hours since the rinse conditioner bath was
unable to promote the formation of a substantially uniform zinc
phosphate coating on the surface of Steel Panel Y.
[0042] Referring to FIG. 4, this is a top elevation view of the
surface 18 of Steel Panel Z after Steel Panel Z was phosphatized
with CHEMFOS 700AL. Unlike Steel Panel Y, Steel Panel Z contained
an extensive number of nodular crystalline structures similar to
those observed in Steel Panels D and E. The formation of the
nodular crystalline structures 20 (i.e., the zinc phosphate
coating) on the surface 18 of Steel Panel Z was promoted by the
rinse conditioner bath of Bath B. Unlike the rinse conditioner bath
of Bath A, however, the rinse conditioner bath of Bath B was
active, even after 24 hours, due to the addition of ferrous iron to
the rinse conditioner bath of Bath B.
* * * * *