U.S. patent application number 10/831581 was filed with the patent office on 2004-11-11 for method for preparing and using silicate systems to treat electrically conductive surfaces and products obtained therefrom.
Invention is credited to Bass, Jonathan L., Chandran, Ravi, Heimann, Nancy G., Heimann, Robert L., Soucie, Wayne L..
Application Number | 20040222105 10/831581 |
Document ID | / |
Family ID | 33425177 |
Filed Date | 2004-11-11 |
United States Patent
Application |
20040222105 |
Kind Code |
A1 |
Heimann, Robert L. ; et
al. |
November 11, 2004 |
Method for preparing and using silicate systems to treat
electrically conductive surfaces and products obtained
therefrom
Abstract
The disclosure relates to treating a silicate medium and using
the treated medium for improving the surface of metallic or
electrically conductive materials. The treated medium provides a
silicate medium having a defined degree of polymerization and
predetermined quantities of the desired silicate polymer. The
treated silicate medium can be employed in an electroless or
electrolytic process.
Inventors: |
Heimann, Robert L.;
(Centralia, MO) ; Soucie, Wayne L.; (Columbia,
MO) ; Bass, Jonathan L.; (Audobon, PA) ;
Chandran, Ravi; (New Brunswick, NJ) ; Heimann, Nancy
G.; (Centralia, MO) |
Correspondence
Address: |
ORSCHELN MANAGEMENT CO
P O BOX 280
2000 US HIGHWAY 63 SOUTH
MOBERLY
MO
65270
|
Family ID: |
33425177 |
Appl. No.: |
10/831581 |
Filed: |
April 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60465414 |
Apr 25, 2003 |
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60510230 |
Oct 8, 2003 |
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60528034 |
Dec 9, 2003 |
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Current U.S.
Class: |
205/674 ;
205/705 |
Current CPC
Class: |
C25D 9/04 20130101; C23C
28/00 20130101; C23C 28/04 20130101; C23C 26/00 20130101 |
Class at
Publication: |
205/674 ;
205/705 |
International
Class: |
C25F 001/00 |
Claims
The following is claimed:
1. A method for treating a substrate having an electrically
conductive surface comprising: preparing a medium comprising water
and at least one silicate and wherein the medium has a basic pH,
passing a current through the medium and then; contacting at least
a portion of the surface with the medium.
2. The method of claim 1 wherein the medium further comprises
colloidal silica, and wherein the medium is substantially free of
chromates and VOCs.
3. A method for treating a metallic or an electrically conductive
surface comprising: preparing a medium comprising water and at
least one silicate and wherein the medium has a basic pH, placing
an anode and a cathode in electrical contact with the medium,
exposing at least a portion of the surface to a medium, passing a
current through the medium wherein the surface is not in direct
contact with the anode or cathode.
4. The method of claim 3 wherein the colloidal silica has a
particle size of less than about 50 nanometers.
5. The method of claim 1 wherein the surface comprises at least one
member selected from the group consisting of copper, nickel, tin,
iron, zinc, aluminum, magnesium, stainless steel and steel and
alloys thereof.
6. The method of claim 1 further comprising drying and rinsing and
said rinsing comprises contacting the surface with a second medium
comprising a combination comprising water and at least one water
soluble compound selected from the group consisting of carbonates,
chlorides, fluorides, nitrates, zironates, titanates, sulphates,
water soluble lithium compounds and silanes.
7. The method of claim 1 wherein the medium comprises at least one
dopant selected from the group consisting of zinc, cobalt,
molybdenum, nickel and aluminum.
8. The method of claim 6 wherein said drying is conducted at a
temperature of at least about 120C.
9. The method of claim 5 wherein said surface comprises zinc or
zinc alloys.
10. The method of claim 1 wherein said surface comprises a
chromated surface.
11. The method of claim 3 wherein the surface comprises a chromated
surface.
12. The method of claim 3 wherein said medium further comprises at
least one water dispersible polymer.
13. The method of claim 1 wherein said method further comprises
contacting with at least one acid.
14. The method of claim 9 wherein said surface comprises zinc
nickel alloys.
15. The method of claim 1 further comprising pretreating the
surface prior to said contacting.
16. The method of claim 1 further comprising applying at least one
coating selected from the group consisting of latex, silanes,
epoxies, silicone, amines, alkyds, urethanes, polyester and
acrylics.
17. The method of claim 15 wherein the pretreating comprises
contacting the surface with at least one member selected from the
group consisting of sodium acetate, aluminum ammonium sulfate,
aluminum phosphate, aluminum nitrate, aluminum fluoride, aluminum
potassium sulfate, aluminum tartate, sodium ammonium phosphate and
sodium gluconate.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/465,414, filed Apr. 25, 2003, U.S. Provisional
Application No. 60/510,230, filed on Oct. 08, 2003 and U.S.
Provisional Application No. 60/528,034, filed on Dec. 09, 2003. The
disclosure of the previously identified Provisional Applications is
hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The instant invention relates to preparing silicate mediums
and using silicate mediums for modifying the surface of metals and
other electrically conductive materials.
BACKGROUND OF THE INVENTION
[0003] Silicates have been used in electrocleaning operations to
clean steel, tin, among other surfaces. Electrocleaning is
typically employed as a cleaning step prior to an electroplating
operation. Usage of silicates for cleaning described in "Silicates
As Cleaners In The Production of Tinplate" is described by L. J.
Brown in February 1966 edition of Plating; European Patent No.
00536832/EP B1 (Metallgesellschaft AG); and U.S. Pat. Nos.
5,902,415, 5,352,296 and 4,492,616.
[0004] Processes for electrolytically forming a protective layer or
film by using an anodic method are disclosed by U.S. Pat. No.
3,658,662 (Casson, Jr. et al.), and United Kingdom Pat. No.
498,485. U.S. Pat. No. 5,352,342 to Riffe, which issued on Oct. 4,
1994 and is entitled "Method And Apparatus For Preventing Corrosion
Of Metal Structures", describes using electromotive forces upon a
zinc solvent containing paint. U.S. Patent Nos. 5,700,523, and
5,451,431; and German Patent No. 93115628 describe processes for
using alkaline meta-silicates to treat metallic surfaces. All of
the aforementioned patents, patent applications and publications
are hereby incorporated by reference.
[0005] There is a need in this art for an environmentally benign
metal treatment (e.g., substantially chromate free) that imparts
corrosion resistance to metallic surfaces.
CROSS REFERENCE TO RELATED AND COMMONLY ASSIGNED PATENTS AND PATENT
APPLICATIONS
[0006] The subject matter herein is related to the following
commonly assigned patents and patent applications: U.S. Pat. Nos.
6,149,794; 6,258,243; 6,153,080; 6,322,687; 6,572,756B2 and U.S.
patent application Ser. Nos. 09/816,879; 09/775,072; 09/814,641;
10/211,051; 10/211,094; 10/211,029 and 10/359,402. The disclosure
of the foregoing patents and patent applications is hereby
incorporated by reference.
SUMMARY OF THE INVENTION
[0007] Broadly, the instant invention relates to treating a
silicate medium and using the treated medium for improving the
surface of metallic or electrically conductive materials. The
treated silicate medium can be employed in an electroless or
electrolytic process.
[0008] By "electroless" it is meant that the treated silicate
medium is used in a metal or surface treatment process wherein no
current is applied from an external source (a current may be
generated in-situ due to an interaction between the metallic
surface and at least one medium). By "electrolytic" or
"electrodeposition" or "electrically enhanced", as used herein it
is meant to refer to an environment created by introducing or
passing an electrical current through a silicate containing medium
while the metallic or electrically conductive surface contacts the
silicate medium (but not in direct contact with an electrode).
Electrolytic also means passing a current through a silicate medium
while in contact with the electrically conductive substrate (or
having an electrically conductive surface). By "metal containing",
"metal", or "metallic", it is meant to refer to sheets, shaped
articles, fibers, rods, particles, continuous lengths such as coil
and wire, metallized surfaces or electrically conductive films,
among other configurations that are based upon at least one metal
and alloys including a metal having a naturally occurring, or
chemically, mechanically or thermally modified surface. Typically a
naturally occurring surface (e.g., a passivating film), upon a
metal or metallized surface will comprise a thin film or layer
comprising at least one oxide, hydroxides, carbonates, sulfates,
chlorides, among others. The naturally occurring surface can be
removed or modified by using the inventive process. The metal
containing surface refers to a metal article or body as well as a
non-metallic member having an adhered metal or a conductive layer.
While any suitable surface can be treated by the inventive process,
examples of suitable metal surfaces comprise at least one member
selected from the group consisting of galvanized surfaces,
sheradized surfaces (e.g, mechanically plated), zinc, chromium,
iron, steel and other iron alloys, brass, copper, nickel, tin,
aluminum, lead, cadmium, magnesium, silver, barium, beryllium,
calcium, strontium, cadmium, titanium, zirconium, manganese,
cobalt, alloys thereof such as zinc-nickel alloys, tin-zinc alloys,
zinc-cobalt alloys, zinc-iron alloys, among others.
[0009] In some cases, the metal surface has been pretreated with
another metal or compound that can interact with the silicate
medium. While any suitable pretreatment metal or compound can be
used, examples of suitable pretreatments comprise at least one
member selected from the group of aluminum, copper, tin, titanium,
chromium, molybdenum, tungsten, vanadium, selenium, arsenic,
antimony, gold, silver, nitrates, phosphates, organic precursors
thereof, among others. In some cases, the pretreating metal is
delivered to the metal surface via a carrier comprising at least
one member selected from the group consisting of water, at least
one silicate (e.g., sodium silicate), solvent or water dispersible
polymers, electrically conductive polymers, among others.
[0010] If desired, the inventive process can be employed to treat a
non-conductive substrate having at least one surface coated with a
metal, e.g., a metallized polymeric article or sheet, ceramic
materials coated or encapsulated within a metal, among others.
Examples of metallized polymer comprise at least one member
selected from the group of polycarbonate, acrylonitrile butadiene
styrene (ABS), rubber, silicone, phenolic, nylon, PVC, polyimide,
melamine, polyethylene, polyproplyene, acrylic, fluorocarbon,
polysulfone, polyphenyene, polyacetate, polystyrene, epoxy, among
others. Conductive surfaces can also include carbon or graphite as
well as conductive polymers (polyaniline for example).
[0011] The process of using the silicate medium is a marked
improvement over conventional methods by obviating the need for
solvents or solvent containing systems to form a corrosion
resistant film or layer, e.g., a mineral layer. In contrast, to
conventional methods the inventive process can be substantially
solvent free. By "substantially solvent free" it is meant that less
than about 5 wt. %, and normally less than about 1 wt. % volatile
organic compounds (V.O.C.s) are present in the electrolytic
environment. The inventive process is also a marked improvement
over conventional methods by reducing, if not eliminating, chromate
and/or phosphate containing compounds (and issues attendant with
using these compounds such as waste disposal, worker exposure,
among other undesirable environmental impacts). While the inventive
process can be employed to enhance chromated or phosphated
surfaces, the inventive process can replace these surfaces with a
more environmentally desirable surface (e.g., a treating a
trivalent chromate containing surface with the inventive process).
The inventive process, therefore, can be "substantially chromate
free" and "substantially phosphate free" and in turn produce
articles that are also substantially chromate (hexavalent and
trivalent) free and substantially phosphate free. The inventive
process can also be substantially free of heavy metals such as
chromium, cobalt, lead, cadmium, barium, among others. By
substantially chromate free, substantially phosphate free and
substantially heavy metal free it is meant that less than 5 wt. %
and normally about 0 wt. % chromates, phosphates and/or heavy
metals are present in a process for producing an article or the
resultant article.
[0012] The process of using the silicate medium can provide an
improved surface upon metallic or electrically conductive
materials. The improved surface can comprise a first film or layer
(including a colloidal layer on a metal or conductive polymer), in
contact with the surface, which may comprise a metal silicate and a
second film or layer upon the first that comprises at least one
siliceous species (e.g., as described in Pages 83-94 of R. K. Iler,
"The Chemistry of Silica: Solubility, Polymerization, Colloid and
Surface Properties, and Biochemistry", John Wiley & Sons, NY,
1979; Page 86 of Englehardt and Michel, "High Resolution Solid
State NMR of Silicates and Zeolites" John Wiley & Sons, NY
1987; and Bass and Turner "Anion Distribution In Sodium Silicate
Solutions. Charateristization By Si29NMR And Infrared
Spectroscopies And Vapor Phase Osmometry", Journal of Physical
Chemistry B, 1997 Vol 101(50), Pages 10638 to 10644; all hereby
incorporated by reference). A silica containing film or coating can
then be deposited upon the mono or disilicate film as a monomeric
silica species (e.g., monomeric, dimer or oligomeric siliceous
species). The silica containing film or coating may also include
colloidal silica. The colloidal silica can be generated in situ
(e.g., in an electrolytic process adjacent to the Helmholtz zone of
the anode), or added to the silicate medium.
BRIEF SUMMARY OF THE DRAWINGS
[0013] FIG. 1 is an SEM photomicrograph illustrating a potential
defect that may be associated with the presence of hydrogen. FIG. 2
is a graphical representation of an NMR scan of a silicate medium
before being used to treat metal components. FIG. 3 is a graphical
representation of an NMR scan of the silicate medium of FIG. 2
after treating metal components. FIG. 4 is a schematic drawing of a
barrel apparatus for treating metal containing material in
accordance with one aspect of the invention.
DETAILED DESCRIPTION
[0014] The instant invention improves the previously disclosed
processes by providing a silicate medium having a defined degree of
polymerization and predetermined quantities of the desired silicate
polymer (e.g., the instant invention can increase or decrease
silicate polymerization in order to obtain the desired
concentration and type of silicate species). The inventive method
comprises exposing the silicate medium to a current source for a
time and under conditions sufficient to obtain the desired degree
and concentration of polymerized silicate (e.g., oligomers ranging
from monomeric [Q0] to tetramers [Q4] and colloids). The silicate
medium can be used for improving the surface characteristics of
metallic or electrically conductive materials. The silicate medium
can be exposed to a current source before, during or after
contacting a metallic surface with the silicate medium. The degree
of polymerization or speciation can be obtained or modified by
varying the pH (e.g., by increasing the pH by adding a caustic
compound such as sodium hydroxide, TMOH, among others), or, in the
case of sodium silicate, by varying the ratio of sodium to silicon
in the medium. The degree of polymerization or speciation can also
be modified by applying a current greater than the over potential
of water so that hydrogen and oxygen are introduced into the
silicate medium. The presence of hydrogen can increase the pH of
the medium on a localized basis which in turn can cause silica
depolymerization. The pH of the medium can also be increased by
adding a caustic (e.g., sodium hydroxide, TMOH, etc.) which also
can cause silica depolymerization and change the concentration of
siliceous species.
[0015] The compositions and processes described in the
aforementioned Cross Referenced Patents And Patent Applications
employ silicate containing mediums for improving the surface of a
metal. These processes may form a mineral-like metal disilicate
upon the metal surface and a silica containing surface upon the
disilicate. When a zinc surface is contacted with the silicate
medium, a metal silicate, e.g., zinc silicate layer can formed by
an interaction between certain oligimers or silicate species within
the silicate medium. The silicate oligomers or silicate speciation
can range from Q0 for monomeric, Q1 for dimeric silica groups, Q2
for trimeric silica groups or species (that can include at anion)
to Q4 for polymer. When interacting the silicate medium with a zinc
surface, a silicate medium comprising Q0 and Q1 species is
desirable. The instant invention can be employed in order to obtain
a silicate medium having a desirable concentration of Q0 and Q1
species. The type and concentration of silicate species can vary
depending upon the chemistry of the surface exposed to the silicate
medium.
[0016] By treating or electrifying the silicate medium, the
inventive method can reduce potential defects that can be
associated with hydrogen (e.g., hydrogen embrittlement, cracking,
non-uniform films, among potential defects associated with in-situ
hydrogen evolution). Further, a metallic surface that is treated by
the inventive process can possess improved corrosion resistance,
increased electrical resistance, heat resistance (including to
molten metals), flexibility, resistance to stress crack corrosion,
adhesion to sealer, paints and topcoats, among other
properties.
[0017] When a silicate medium is employed in a cathodic
electrolytic process for treating metallic surfaces, hydrogen gas
can evolve upon the surface of the metallic surfaces while silica
containing material is precipitated. Without wishing to be bound by
any theory or explanation, it is believed that hydrogen bubbles can
adversely affect the deposited silica or become trapped within the
deposited silica. Referring now to FIG. 1, FIG. 1 is an SEM
photomicrograph of what is believed to be a hydrogen bubble trapped
within the deposited silica surface.
[0018] The instant method for treating the silicate medium can be
practiced in the absence of the metal surface to be treated within
the silicate medium. Therefore, in addition to providing a silicate
medium having a desirable concentration of certain silicate
oligomers or species, the instant invention can reduce the amount
of hydrogen present in the silicate medium. While hydrogen may be
undesirable in certain metal treating operations, hydrogen can be
employed in the instant invention in order to obtain a desired
silicate oligomer (e.g., monomer, dimer, etc) and concentration
thereof (e.g., depolymerization of one silicate specie into a more
desirable specie).
[0019] In one aspect of the invention, the silicate medium is
present between or adjacent to an anode and a cathode under
conditions sufficient to evolve hydrogen at the cathode and oxygen
at the anode (e.g., at least equal to the overpotential of water
when using an aqueous carrier). The anode and cathode can be
fabricated from dimensionally stable materials or materials that
contribute desirable compounds or elements (e.g., zinc, nickel,
iron, titanium, aluminum, among others). Examples of dimensionally
stable materials comprise platinum, platinum plated niobium,
platinum plated titanium, iridium oxide, among other materials
stable at a pH of about 10-14.
[0020] While the inventive process for treating the silicate medium
can be practiced in any suitable manner non-limiting examples
comprise treating the silicate in one vessel and pumping into a
container for contacting metallic surfaces, a weir wherein the
silicate is treated and then transferred to contact metallic
surfaces, among other methods for treating the silicate medium
separate from the metallic surface. If desired, the silicate can be
treated in the same vessel as the metallic surfaces provided that
hydrogen evolved from the silicate treatment has been substantially
dehydrogenated or treated in order to substantially remove hydrogen
from the medium (e.g., electrify the silicate solution for about 15
minutes, turn off power and then introduce metal components into
the treated silicate solution, or electrify the silicate solution
while in the presence of the metal components wherein the metal
components are not in direct contact with the anode or
cathode).
[0021] If desired, at least one compound can be added to the
silicate medium for improving the electrical conductivity of the
medium. While any suitable compound or mixtures thereof can be
added to the medium, an example of such a compound comprises TMOH
(TMOH can also be employed as a stabilizer as described below in
greater detail).
[0022] In one aspect of the invention, the silicate treatment is
conducted adjacent to a metal finishing operation (e.g., a barrel,
basket or rack process for treating metallic components in the
silicate medium). The silicate medium is withdrawn from a tank
housing the medium, treated (e.g., electrified) in order to obtain
the desired silicate polymerization and then reintroduced into the
tank. Depending upon the condition of the silicate medium
additional silicate, water, stabilizers, among other materials can
be added to the silicate medium before, during or after being
treated. If desired, the silicate medium can be filtered before,
during or after treatment. Examples of suitable filtration systems
comprises fibers, plates, media, among other filtration techniques.
One suitable filtration example comprises passing the treated or
untreated silicate medium through a media comprising diatomaceous
earth (e.g., Auto-Vac System supplied by Alar Engineering, Mokane,
Ill.).
[0023] In one aspect of the invention, waste filtrate (e.g., used
diatomaceous earth media or filtrate therefrom), or silicate medium
that is undesirable for continued usage in treating metal surfaces
is employed for buffering other metal plating wastes. After
filtration, silicate medium acceptable for reuse is transported to
a metal finishing tank, and unacceptable silicate medium can be
employed for treating metal plating waste streams. That is, the
silicate medium has a basic pH that can be employed for buffering
or precipitating solids from other metal plating processes (e.g.,
zinc plating or chromating waste streams). Employing the silicate
medium for treating metal plating wastes reduces the overall cost
of waste disposal while obtaining additional value from the
silicate medium.
[0024] In a further aspect of the invention, the metal part is
treated while in the silicate medium without being in direct
contact with an anode or a cathode (e.g., the metal part is within
the silicate medium while a current is passed between an anode and
a cathode within the medium). The metal part can be located
between, or adjacent to the anode and/or cathode thereby causing
the metal part can become bipolar. By "bipolar" it is meant that a
portion of the metal part functions as an anode or a cathode or
both depending upon the relationship to the anode and cathode
within the medium. The bipolar nature of the part can vary
depending upon displacement of the metal part and/or electrodes.
The spatial orientation can cause a portion of the metal part to be
exposed to a cathodic environment and another portion of the same
part to be exposed to an anodic environment. This environment can
be created by supplying DC or AC current to the anode and
cathode.
[0025] In another aspect of the invention, the silicate medium is
treated and then introduced (e.g., pumped from a silicate treatment
vessel) into a tank. Metal parts can be introduced into the tank
via a dip-spin basket or container having metal parts. The metal
parts are exposed to the silicate medium for a time and under
conditions sufficient to form the aforementioned improved silicate
surface. If desired, the parts within the container can be
activated or cleaned prior to exposure to the treated silicate
medium. After removal from the silicate medium, the metal parts can
be dried, coated with a sealer or topcoat, among other
post-treatments.
[0026] In some cases, the metal surface has been pretreated with
another metal or compound that can interact with the silicate
medium (e.g., an organic or inorganic film or layer containing the
other metal is applied prior to contact with the silicate medium).
While any suitable pretreatment metal or compound can be used,
examples of suitable pretreatments comprise at least one member
selected from the group of aluminum (e.g., sodium aluminate,
aluminum ammonium sulfate, aluminum fluoride, aluminum nitrate,
aluminum phosphate, aluminum potassium sulfate, aluminum tartrate,
among others), copper, tin, titanium (e.g., titanates), chromium
(e.g., chromates), molybdenum (e.g, molybdates), tungsten,
vanadium, selenium, arsenic, antimony, gold, silver, nitrates,
phosphates (e.g., sodium ammonium phosphate), sodium acetate,
sodium d-gluconate, inorganic or organic precursors thereof, at
least one dopant (described below in greater detail), among others.
In some cases, the pretreating metal is delivered to the metal
surface via a carrier comprising at least one member selected from
the group consisting of water, at least one silicate (e.g., sodium
silicate), solvent or water dispersible polymers, among others. The
concentration of the pretreating metal within the carrier (e.g.,
water) can vary but is normally about 0.001 wt % to about 5.0 wt. %
(e.g., about 0.5 wt %). If desired, the pretreating metal is
dissolved in at least one acid such as HCl, muratic, nitric, among
others. In one aspect of the invention, an iron or a steel surface
is pretreated with a phosphate (e.g., sodium polyphosphate), and
then exposed to the silicate medium. The time and temperature of
the pretreatment can vary depending upon the desired results and
concentration of the metal (e.g., about 10 to about 90 seconds
[normally about 30 seconds] under ambient conditions).
[0027] In one aspect, the surface is pretreated with an inorganic
film or layer. The inorganic film or layer can comprise at least
one of the aforementioned pretreating metals. The inorganic film or
layer can be formed by any suitable process. An example of a
suitable process comprises one of the processes disclosed in the
aforementioned Cross-Referenced Patents And Patent Applications
(e.g., a zinc or zinc alloy surface is exposed to an electrolytic
silicate medium and then by the inventive process). Another example
of a suitable process comprises forming a film or layer by contact
with a potassium silicate containing solution.
[0028] Without wishing to be bound by any theory or explanation, it
is believed that the film or layer formed by pretreating the
surface can interact with the silicate medium (e.g., by ion
exchanging). That is, it is believed that the film or layer can
comprise metal species capable of ion exchange with the silicate
medium (e.g., sodium silicate with zincate balanced sodium to form
silica films/colloids).
[0029] The silicate medium can comprise water and at least one
water soluble silicate such as at least one member selected from
the group of sodium silicate, potassium silicate, lithium silicate,
ammonium silicate, tetramethylammonium silicates, tetraakylammonium
silicates, tetrabutylammonium silicates, among other silicates,
siliceous species such as monomeric silica, oligomeric silica,
polymeric silica, colloidal silica, among other water silicates and
combinations thereof. While any suitable silicate can be employed,
an example of suitable silicate comprises an oligomeric sodium
silicate (e.g., available commercially from PQ Corporation as "D"
grade sodium silicate). The oligomeric sodium silicate has a ratio
of SiO2 wt./Na2Owt of about 2.00 wherein the amount of NaOw/w % is
about 13 to about 15 (e.g., about 14.7+-0.15) and the amount of
SiO2w/wt % is about 28 to about 30 (e.g., about 29.4). The amount
of at least one water soluble silicate normally comprises about 1
to about 30 wt. % of the first medium. If present in the silicate
medium, the siliceous species (e.g,. colloidal silica, monomeric or
oligomeric silica-containing species) can have any suitable size
and, normally, range from about 10 to 200 nanometers (e.g., about
15 to about 90 nm). The silicate medium has a pH of about 10 to 14
(e.g., about 11.5).
[0030] In one aspect of the invention, a commercially available
sodium silicate (N Grade sodium silicate which has SiO2 wt/Na2Owt
ratio of 3:22 and a lower viscosity relative to oligomeric silicate
[D-Grade]) is combined with D-grade sodium silicate in order to
obtain the silicate medium. A blend of N-Grade and D-Grade sodium
silicate can be employed to tailor the pH, degree and range of
silicate polymerization, cost, among other parameters of the
inventive silicate medium. The addition of at least one stabilizer
such as TMOH (e.g., about 25 wt. % to either N-grade or D-grade
sodium silicate or mixtures thereof) can change the SiO2: alkali
ratio of the medium thereby enhancing condensation of silica
species onto a metal surface (e.g., a non-amphortic metal
surface).
[0031] The silicate medium can further comprise at least one
stabilizer. The stabilizer is employed for controlling or
inhibiting growth of colloidal silica. Without wishing to be bound
by any theory or explanation it is believed that dimer, trimer and
other oligomeric forms present in the silicate medium can
agglomerate or grow into colloidal silica. The stabilizer inhibits
colloidal growth thereby maintaining the desired silicate
polymerization within the silicate medium. While any suitable
stabilizer can be employed, examples of such stabilizers comprise
at least one member selected from the group of tetraalkylammonium
hydroxides such as tetramethyl, tetraethyl, tetrapropyl and
tetrabutyl ammonium hydroxides. The amount of stabilizer can vary
depending upon the composition of the stabilizer, condition of
silicate medium to which stabilizer is introduced, among other
parameters (e.g,. about 1% to 50 wt. % stabilizer). A non-limiting
example of a stabilized silicate medium comprises a blend of 4.78
gal H2O, 2.58 gal sodium silicate (N-Grade sodium silicate), and
2.24 gal tetramethylammonium hydroxide (TMAOH).
[0032] The specific electrolytic parameters used within the
silicate medium depend upon the composition of the medium, extent
to which the medium has been used for treating metallic materials,
time, temperature, flow rate, among other parameters. Normally, the
temperature of the medium ranges from about 25 to about 95 C (e.g.,
about 75C), the voltage from about 6 to 24 volts, with a silicate
solution concentration from about 1 to about 15 wt. % silicate
(e.g., about 10 wt. % sodium silicate), the current density ranges
from about 0.025A/in2 and greater than 0.60A/in2 and typically
about 0.04A/in2 (e.g., about 180 to about 200 mA/cm2 and normally
about 192 mA/cm2), contact time with the first medium from about 10
seconds to about 50 minutes and normally about 1 to about 15
minutes, and anode to cathode surface area ratio of about 0.5:1 to
about 2:1 (e.g., 1:1). Depending upon whether a bipolar medium is
desired, DC or AC current can be supplied to the silicate
medium.
[0033] In an aspect of the invention, the silicate medium can be
modified to include at least one dopant material (e.g., to improve
corrosion resistance, reduce torque tension, increase heat
resistance, among other chemical and physical properties). Dopants
can be added before, during or after treatment in accordance with
the instant invention (e.g., the previously described metal
pretreatment). The dopants can be useful for building additional
thickness of the film or layer obtained when exposing metallic
articles to the silicate medium. The amount of dopant can vary
depending upon the properties of the dopant and desired results.
Typically, the amount of dopant will range from about 0.001 wt. %
to about 5 wt. % (or greater so long as the deposition rate is not
adversely affected). Examples of suitable dopants comprise at least
one member selected from the group of water soluble salts, oxides
and precursors of tungsten, molybdenum, titanium (titatantes),
zircon, vanadium, phosphorus, aluminum (aluminates), iron (e.g.,
iron chloride), boron (borates), bismuth, gallium, tellurium,
germanium, antimony, niobium (also known as columbium), magnesium
and manganese, sulfur, zirconium (zirconates) mixtures thereof,
among others, and usually, salts and oxides of aluminum and iron,
and other water soluble or dispersible monovalent species. The
dopant can comprise at least one of molybdenic acid, fluorotitanic
acid and salts thereof such as titanium hydrofluoride, ammonium
fluorotitanate, ammonium fluorosilicate and sodium fluorotitanate;
fluorozirconic acid and salts thereof such as H.sub.2ZrF.sub.6,
(NH.sub.4).sub.2ZrF.sub.6 and Na.sub.2ZrF.sub.6; among others.
Alternatively, dopants can comprise at least one substantially
water insoluble material such as electropheritic transportable
polymers, PTFE, boron nitride, silicon carbide, silicon nitride,
aluminum nitride, titanium carbide, diamond, titanium diboride,
tungsten carbide, metal oxides such as cerium oxide, powdered
metals and metallic precursors such as zinc, among others.
[0034] The aforementioned dopants can also be employed for
modifying the chemistry of the silicate medium and/or physical
properties of the silicate film or layer formed on the metallic
surface, as a diluent for the medium, among others. Additional
examples of such dopants are iron salts (ferrous chloride, sulfate,
nitrate), aluminum fluoride, fluorosilicates (e.g., K2SiF6),
fluoroaluminates (e.g., potassium fluoroaluminate such as
K2AlF5-H2O), mixtures thereof, among other sources of metals and
halogens. The dopant materials can be introduced to the metal
surface in pretreatment steps and/or post treatment steps
(described below in greater detail), and/or by alternating exposing
the metal surface to solutions of dopants and solutions of the
silicate medium.
[0035] The silicate medium can also be modified by adding at least
one diluent. Similar to the dopant, the diluent can be added
before, during or after treating the silicate medium in accordance
with the instant invention. Examples of suitable diluent comprise
at least one member selected from the group of sodium sulphate,
surfactants, de-foamers, colorants/dyes, conductivity modifiers,
among others. The diluent (e.g., sodium sulfate) can be employed
for reducing the affects of contaminants entering the medium,
reducing bath foam, among others. When the diluent is employed as a
defoamer, the amount normally comprises less than about 5 wt. % of
the medium, e.g., about 1 to about 2 wt. %.
[0036] In one aspect of the invention, exposing metallic materials
to the treated silicate medium of the invention is preceded and/or
followed by procedures known in this art such as cleaning or
rinsing, e.g., immersion/spray within the treatment, sonic
cleaning, double counter-current cascading flow; alkali or acid
treatments, among other treatments. By employing a suitable post-
or pre-treatment the solubility, corrosion resistance (e.g.,
reduced white rust formation when treating zinc containing
surfaces), sealer and/or topcoat adhesion, among other properties
of treated metallic surface formed by the inventive method can be
improved. If desired, the post-treated surface can be sealed,
rinsed and/or topcoated, e.g., silane, epoxy, latex, fluoropolymer,
acrylic, among other coatings.
[0037] In one aspect of the invention, a pre-treatment comprises
exposing the metallic surface or substrate to be treated to at
least one of an acid, oxidizer, a basic solution (e.g., potassium
or sodium hydroxide) among other compounds. The pre-treatment can
be employed for removing excess oxides or scale, equipotentialize
the surface for subsequent mineralization treatments, hydroxylize,
convert the surface into a silicate containing or silica containing
precursor, among other benefits. Conventional methods for acid
cleaning metal surfaces are described in ASM, Vol. 5, Surface
Engineering (1994), and U.S. Pat. No. 6,096,650; hereby
incorporated by reference.
[0038] In another aspect of the invention, the metal surface is
pre-treated or cleaned electrolytically by being exposed to an
anodic environment. That is, the metal surface is exposed to the
medium wherein the metal surface is the anode and a current is
introduced into the medium. If desired, anodic cleaning can occur
within the silicate medium. By using the metal as the anode in a DC
cell and maintaining a current of about 10A/ft2 to about 150A/ft2,
the process can generate oxygen gas. The oxygen gas agitates the
surface of the workpiece while oxidizing the substrate's surface.
The surface can also be agitated mechanically by using conventional
vibrating equipment. If desired, the amount of oxygen or other gas
present during formation of the mineral layer can be increased by
physically introducing such gas, e.g., bubbling, pumping, among
other means for adding gases.
[0039] In a further aspect of the invention, the metal part is
pretreated to have a darkened appearance. The darkened part can be
treated in accordance with the instant invention (e.g., exposure to
a silicate medium and/or bipolar environment). The darkened part,
which has been exposed to the instant silicate medium, provides a
desirable surface for secondary coatings; especially for dark or
black secondary coatings (e.g., cathodic lacquers such as those
commercially available from PPG). Examples of suitable darkening
processes comprise exposing the metal surface to a dye, anodizing,
chemical reactants (e.g., molybdate compounds), among other process
effective at causing the metal surface to have a relatively dark
surface. A suitable anodizing process is described in "Zinc
Anodizing" by Wolfgang Paatsch, June 1995-Metal Finishing; hereby
incorporated by reference. Commercial darkening compounds are
available from Jost Chemicalas Insta-Blak Z360. In most cases it is
desirable to pre-treat or clean the parts prior to the darkening
process (e.g., by immersion with dilute nitric acid, ammonium
citrate, citric acid, among others). While any darkening process
can be employed, one example comprises exposing a zinc containing
part to an electrolyte comprising 20 g/L NaOH and 5 g/L NaClO2 and
applying an AC current having a current density of about 40A/dm2.
The electrolyte is maintained at a temperature of about 30C and the
process operated for about 40 minutes. The darkened and silicate
treated parts can be dried at a temperature and time sufficient to
remove water (e.g., for about 4 minutes at 120C). Without wishing
to be bound by any theory or explanation, it is believed that
combining a darkening process with exposure to the silicate medium
can form a zinc chloride phase (e.g., ZnCl2-4Zn(OH)2) that in turn
imparts improved corrosion resistance.
[0040] If desired, the method for treating metallic materials can
include a thermal post-treatment following exposure to the silicate
medium. The metal surface can be removed from the medium, dried
(e.g., at about 120 to about 150C for about 2.5 to about 10
minutes), rinsed in deionized water and then dried. The dried
surface may be processed further as desired; e.g. contacted with a
sealer, rinse or topcoat. Typically the amount of heating in drying
steps herein is sufficient to consolidate or densify the inventive
surface without adversely affecting the physical properties of the
underlying metal substrate. Heating can occur under atmospheric
conditions, within a nitrogen containing environment, among other
gases. Alternatively, heating can occur in a vacuum. The surface
may be heated to any temperature within the stability limits of the
surface coating and the surface material. Typically, surfaces are
heated from about 75.degree. C. to about 250.degree. C., more
typically from about 120.degree. C. to about 200.degree. C. If
desired, the heat treated component can be rinsed in water to
remove any residual water soluble species and then dried again
(e.g., dried at a temperature and time sufficient to remove rinse
water).
[0041] In one aspect of the invention, a post treatment following
exposure to the treated silicate medium comprises exposing the
substrate to a source comprising at least one acid source or
precursors thereof. Examples of suitable acid sources comprise at
least one member chosen from the group of phosphoric acid,
hydrochloric acid, molybdic acid, silicic acid, acetic acid, citric
acid, nitric acid, hydroxyl substituted carboxylic acid, glycolic
acid, lactic acid, malic acid, tartaric acid, ammonium hydrogen
citrate, ammonium bifluoride, fluoboric acid, fluorosilicic acid,
glacial acetic acid, among other acid sources effective at
improving at least one property of the treated metal surface. The
pH of the acid post treatment may be modified by employing at least
one member selected from the group consisting of ammonium citrate
dibasic (available commercially as Citrosol.RTM. #503 and
Multiprep.RTM.), fluoride salts such as ammonium bifluoride,
fluoboric acid, fluorosilicic acid, among others. The acid post
treatment can serve to activate the surface thereby improving the
effectiveness of rinses, sealers and/or topcoatings (e.g., surface
activation prior to contacting with a sealer can improve cohesion
between the surface and the sealer thereby improving the corrosion
resistance of the treated substrate). The acid post treatment can
also function to reduce any adverse interaction between the treated
surface and an overlying sealer or coating that is sensitive to a
basic pH. Normally, the acid source will be water soluble and
employed in amounts of up to about 15 wt. % and typically, about 1
to about 5 wt. % and have a pH of less than about 5.5.
[0042] If desired, after contacting the silicate medium the surface
can be rinsed; typically after being dried. By "rinse" it is meant
that an article or a treated surface is sprayed, dipped, immersed
or other wise exposed to the rinse in order to affect the
properties of the treated surface. For example, a surface treated
by the inventive process is immersed in a bath comprising at least
one rinse. In some cases, the rinse can interact or react with at
least a portion of the treated surface. Further the rinsed surfaced
can be modified by multiple rinses, heating, topcoating, adding
dyes, lubricants and waxes, among other processes. Examples of
suitable compounds for use in rinses comprise at least one member
selected from the group of titanates, titanium chloride, tin
chloride, zirconates, zirconium acetate, zirconium oxychloride,
fluorides such as calcium fluoride, tin fluoride, titanium
fluoride, zirconium fluoride; coppurous compounds, ammonium
fluorosilicate, metal treated silicas (e.g., Ludox.RTM. products
such as Ludox.RTM. CL), nitrates such as aluminum nitrate;
sulphates such as magnesium sulphate, sodium sulphate, zinc
sulphate, and copper sulphate; lithium compounds such as lithium
acetate, lithium bicarbonate, lithium citrate, lithium metaborate,
lithium vanadate, lithium tungstate, silanes, among others. The
rinse can further comprise at least one organic compound such as
vinyl acrylics, fluorosurfactancts, polyethylene wax, among others.
One specific rinse comprises water, water dispersible urethane, and
at least one silicate, e.g., refer to commonly assigned U.S. Pat.
No. 5,871,668; hereby incorporated by reference. While the rinse
can be employed neat, normally the rinse will be dissolved, diluted
or dispersed within another medium such as water, organic solvents,
among others. While the amount of rinse employed depends upon the
desired results, normally the rinse comprises about 0.1 wt % to
about 50 wt. % of the rinse medium. The rinse can be employed as
multiple applications and, if desired, heated. Moreover, the
aforementioned rinses can be modified by incorporating at least one
dopant, e.g. the aforementioned dopants. The dopant can employed
for interacting or reacting with the treated surface. If desired,
the dopant can be dispersed in a suitable medium such as water and
employed as a rinse.
[0043] In one aspect, a post-treatment comprises exposing the
treated surface to at least one compound that absorbs, adsorbs or
chemically removes water from the treated surface. While any
suitable compound or method can be employed, an example comprises
rinsing the treated surface with at least one silane containing
solution. Water can be removed from the treated surface, in the
case of barrel processed parts, by spinning the parts, rinsing in a
silane containing solution and spinning again.
[0044] If desired, after an optional rinsing step at least one
secondary coating can be applied. Examples of suitable such
coatings comprise at least one member selected from the group of
Aqualac.RTM. (urethane containing aqueous solution), W86.RTM.,
W87.RTM., B37.RTM., T01.RTM., E10.RTM., B17, B18 among others (a
heat cured coating supplied by the Magni.RTM. Group), JS2030S
(sodium silicate containing rinse supplied by MacDermid
Incorporated), JS2040I (a molybdenum containing rinse also supplied
by MacDermid Incorporated), EnSeal.RTM. C-23 (an acrylic based
coating supplied by Enthone), EnSeal.RTM. C-26, Enthone.RTM. C-40
(a pigmented coating supplied Enthone), Microseal.RTM.,
Paraclene.RTM. 99 (a chromate containing rinse), EcoTri.RTM. (a
silicate/polymer rinse), MCI Plus OS (supplied by Metal Coatings
International), silanes (e.g., at least one of Dow Corning
Z-6040Z6137 and QP8-5314, and Gelest SIA 0610.0),
tetra-ortho-ethyl-silicate (TEOS), bis-1,2-(triethoxysilyl) ethane
(BSTE), vinyl silane or aminopropyl silane, epoxy silanes,
vinyltriactosilane, alkoxysilanes, among other organo functional
silanes), ammonium zirconyl carbonate (e.g., Bacote 20), urethanes
(e.g., Agate L18), acrylic coatings (e.g., IRILAC.RTM.), e-coats
(e.g., PPG Powercron), silanes including those having amine,
acrylic and aliphatic epoxy functional groups, latex, urethane,
epoxies, silicones, alkyds, phenoxy resins (powdered and liquid
forms), radiation curable coatings (e.g., UV curable coatings),
lacquer including cathodically applied lacquers, shellac, linseed
oil, torque tension modifiers (e.g., TNT15 from MacDermid),
commercially available coatings such as Technicaq 330, Techniseal
448 and Briteguard RP-90, among others. Coatings can be solvent or
water borne systems. These coatings can be applied by using any
suitable conventional method such as immersing, dip-spin, spraying,
among other methods. The secondary coatings can be cured by any
suitable method such as UV exposure, heating, allowed to dry under
ambient conditions, among other methods. An example of UV curable
coating is described in U.S. Pat. Nos. 6,174,932; 6,057,382;
5,759,629; 5,750,197; 5,539,031; 5,498,481; 5,478,655; 5,455,080;
and 5,433,976; hereby incorporated by reference. The secondary
coatings can be employed for imparting a wide range of properties
such as improved corrosion resistance to the underlying mineral
layer, reduce torque tension, a temporary coating for shipping the
treated work-piece, decorative finish, static dissipation,
electronic shielding, hydrogen and/or atomic oxygen barrier, among
other utilities. The treated and coated metal, with or without the
secondary coating, can be used as a finished product or a component
to fabricate another article.
[0045] The thickness of the rinse, sealer and/or topcoat can range
from about 0.00010 inch to about 0.00025 inch. The selected
thickness varies depending upon the end use of the coated article.
In the case of articles having close dimensional tolerances, e.g.,
threaded fasteners, normally the thickness is less than about
0.00005 inch.
[0046] In another aspect of the invention, a metal part is exposed
to a silicate medium and then coated with at least two secondary
coatings. If desired, the silicate medium can be operated in a
bipolar environment. One example comprises exposing zinc plate
parts (e.g., rivets) to a bipolar silicate medium for about 3.5
minutes, drying the parts, rinsing with water, drying, applying a
first coating comprising sodium silicate with aluminum and
magnesium (e.g., available commercially from A-Bright as Briteguard
RP-90), drying the first coating, applying a second coating
comprising at least one silane (e.g., DowCorning Z6137), drying the
second coating and applying a third coating comprising a polymer
and wax composition (e.g., available commercially as MacDermid
TNT). This multiple coating system can achieve improved corrosion
resistance when measuring in accordance with ASTM B-117 (e.g.,
greater than 200 hours until appearance of white rust or zinc
corrosion products).
[0047] In another aspect of the invention, the metal part is
exposed to a silicate medium and then electrolytically coated.
Examples of electrolytically coating comprise at least one of
e-coats, cathodic lacquers (e.g., commercially available as
PPG.RTM. Black Powerseal XL), among others. If desired, the metal
part can be darkened prior to exposure to the silicate medium. That
way a darkened part is provided which can be coated with a dark or
black coating (e.g., to ensure that a relatively light colored
surface is not visible through a relatively dark coating).
[0048] Exposure to the treated silicate medium of the invention can
provide a surface that improves adhesion between a treated
substrate and an adhesive. Examples of adhesives comprise at least
one member selected from the group consisting of hot melts such as
at least one member selected from the group of polyamides,
polyimides, butyls, acrylic modified compounds, maleic anhydride
modified ethyl vinyl acetates, maleic anhydride modified
polyethylenes, hydroxyl terminated ethyl vinyl acetates, carboxyl
terminated ethyl vinyl acetates, acid terpolymer ethyl vinyl
acetates, ethylene acrylates, single phase systems such as
dicyanimide cure epoxies, polyamide cure systems, lewis acid cure
systems, polysulfides, moisture cure urethanes, two phase systems
such as epoxies, activated acrylates polysulfides, polyurethanes,
among others. Two metal substrates having surfaces treated in
accordance with the inventive process can be joined together by
using an adhesive. Alternatively one substrate having the inventive
surface can be adhered to another material, e.g., joining treated
metals to plastics, ceramics, glass, among other surfaces. In one
specific aspect, the substrate comprises an automotive hem joint
wherein the adhesive is located within the hem.
[0049] The inventive process can be used for treating a wide range
of metal surfaces such as discrete components in a barrel, larger
or unusual shaped components on a rack, continuous strips, among
other surfaces. For example, the inventive process can be used for
treating assemblages (e.g., welded structures such as a vehicle
frame) in a method comprising placing the assemblage onto a rack
that transports the assemblage through the method. The assemblage
is cleaned (e.g., with a dilute acid), rinsed with water,
hydroxilized by immersion within a caustic (e.g., dilute sodium
hydroxide), rinsed, and immersed into the inventive silicate medium
(i.e., a previously electrified silicate medium). If desired, a
coating can be applied (e.g., a sealer comprising zinc silicate and
at least one silane), upon the treated surface, and optionally a
second coating comprising an e-coat, a powder paint, among others,
can be applied upon the first coating
EXAMPLES
[0050] The following Examples are provided to illustrate certain
aspects of the invention. These Examples shall not limit the scope
of any claims appended hereto.
Example 1
[0051] This Example illustrates the polymerized silicate species
that interacts with a zinc metal surface. A silicate medium was
used for processing zinc components in accordance with
aforementioned U.S. patent application Ser. No. 09/814,641;
incorporated by reference. The silicate medium was evaluated before
and after treating the zinc components in accordance with
conventional .sup.29Si nuclear magnetic resonance (NMR)
methods.
[0052] Referring now to the Drawings, FIG. 2 illustrates the NMR
spectra of the silicate medium before treating zinc components and
FIG. 3 illustrates the NMR spectra of the silicate medium following
zinc component treatment. FIGS. 2 and 3 include the spectral trace,
integrated peak areas and individual peak data. The relative
amounts of different Si--O linkages in a sample are determined by
comparing the integrated peak areas.
[0053] In each of the spectra there is a series of S-shaped curves
associated with a number. For example, in the spectrum of FIG. 2,
the integrated peak area for the -72.25 ppm peak (assigned to
Q.sup.0, monomer) is 10.00. There is also a series of S-shaped
curves ranging from about -86 ppm to -130 ppm which include three
types of linkages. In order to obtain the integrated area for
polymer, Q.sup.4, it was necessary to subtract the integrated areas
for the other two linkage types. Thus the integrated area for
polymer in this sample is 144.0242.01-29.61-=72.2. The following
table summarizes the integrated peak area data.
1 Integrated % Linkage Integrated % Linkage Area-used Type-used
Area-new Type-new Linkage Type medium medium medium medium Q.sup.0,
monomer 10.0 6.0 10.0 6.6 Q.sup.1, end groups and Q.sup.2.sub.cy3,
middle 3-ring groups 12.44 7.5 13.35 8.9 Q.sup.2.sub.lin,
Q.sup.2.sub.cy4, middle linear and 4-ring groups, 29.61 17.8 31.71
21.1 Q.sup.3.sub.cy3, branching 3-ring groups Q.sup.3.sub.cy4,
branching 4-ring groups 42.01 25.3 44.54 29.6 Q.sup.4 polymer 72.2
43.4 50.76 33.7 Sum of integrated intensities 166.26 150.36
[0054] A description of the different linkage types is found in
Engelhardt and Michel, "High Resolution Solid State NMR of
Silicates and Zeolites, p. 76; hereby incorporated by
reference.
[0055] The data show that the used sample has more polymer and less
of the smaller anions than the new sample. The data also show that
Q0 and Q1 species are more actively involved in an interaction or a
reaction with the zinc surfaces (Q0 can react with zinc to form
willimite and Q1 can react with zinc to form hemimorphite type of
zinc disilicate).
Example 2
[0056] This Example demonstrates treating the silicate medium prior
to contacting metal surfaces in order to obtain a medium having
desirable silicate oligimers and using the treated medium to form a
mineral-like silicate layer.
[0057] The silicate medium was treated by placing an inert anode
and inert cathode in an inert fixture. Specifically, platinum clad
niobium panels of substantially the same dimensions were used for
both the anode and the cathode. The fixture was fabricated from
polyproplyene and installed in a 4 liter beaker set on a hot plate.
A parastolic pump was used to transfer the treated silicate medium
(e.g., at least partially depolymerized sodium silicate) to a
second beaker. The second beaker was used to expose zinc plated
parts to the cathodic process described in U.S. patent application
Ser. No. 09/814,641; hereby incorporated by reference. The second
bath was also placed on a hot plate. Both baths were maintained at
80.degree. C.
[0058] The process was run in both sodium silicate as well as
potassium silicate with varied sodium to silica oxide ratios.
[0059] The corrosion resistance of parts processed in accordance
with the above process were tested by neutral salt fog testing per
ASTM B117. The corrosion resistance was increased from 24 hours
(formation of first white rust corrosion) to 48 hours.
Example 3
[0060] This Example illustrates a barrel apparatus that can be used
for treating metal parts in a bipolar silicate medium. Referring
now to the drawings, FIG. 4 illustrates a process barrel that is
constructed from materials known in the zinc plating art (e.g.,
polypropylene). The process barrel is at least partially filled
with metallic parts such as rivets, fasteners, among other
components conventionally used in barrel metal finishing, and then
inserted into a process tank containing a silicate medium. A
dimensionally stable anode (e.g., constructed from platinum plated
niobium mesh) is located between the process barrel and the sides
of the process tank. The anode and process barrel are connected to
a commercially available rectifier in a manner such that a
cylindrical mesh located about the center longitudinal axis of the
barrel functions as a cathode. A non-conductive mesh is located
concentrically about the cathode mesh in order to allow contact
between the cathode mesh and the silicate medium while preventing
parts from contacting the cathode mesh (e.g., during rotation of
the barrel). When power is supplied to the barrel, anode and
cathode, the metal parts are rotated within a bipolar silicate
medium.
Example 4
[0061] This Examples demonstrates a bipolar process for treating
zinc plated tubular metal rivets. The rivets measured about 0.75
inch by about 1.0 inch. The rivets were pretreated or cleaned
by:
[0062] 1) washing with soap and water,
[0063] 2) agitate within 0.5% nitric acid at room temperature for
30 seconds,
[0064] 3) rinse for 10 seconds in de-ionized water,
[0065] 4) agitate within 38% NaOH at 75C for 30 seconds,
[0066] 5) rinse with 10 seconds with warm tap water.
[0067] A silicate medium was established by adding 10 vol % N-grade
sodium silicate to a bath heated to 75C. The bath measured about 4
by about 4 inches. An anode and cathode each comprising 3.times.6
inch dimensionally stable mesh panels were inserted into the bath.
The pretreated rivets were placed in a polyproplyene and immersed
in the silicate medium. Current was supplied to the anode and
cathode at about 7-9A which achieved a current density of about 0.5
ASI at 15V. The rivets were maintained in the silicate medium for
about 15 minutes. The rivets were dried under atmospheric
conditions in a furnace at 80C for 4 minutes. The dried rivets were
rinsed with tap water for 10 seconds and oven dried again.
Example 5
[0068] Example 4 was repeated except that the silicate medium was
treated with electricity for 15 minutes at 0.5 ASI in accordance
with Example 2 prior to introducing the rivets. The rivets were
immersed within the treated silicate medium having a temperature of
about 80C for a period of about 2 minutes.
Examples 6-10
[0069] These examples demonstrate applying a topcoat upon articles
treated in accordance with the inventive process. The articles
comprised zinc plated rivets measuring 1/8 inch tubular shank with
a 3/4 inch dia. head, and the topcoat comprised a black cathodic
lacquer (available commercially as PPG Black Powerseal XL). Prior
to conducting the inventive process, the articles were chemically
darkened by exposure to one of the following processes: ammonium
molybdate rinse, commercially available solution (e.g., Insta-Blak
Z-360), and anodization. For purposes of comparison, zinc plated
rivets, which were not processed in accordance with the inventive
process, were coated with the cathodic lacquer. The corrosion
performance of all rivets was tested in accordance with ASTM B-119
and the first occurrence of white rust (zinc corrosion products)
was recorded (in general a relatively long period of testing time
before occurrence of white rust corresponds to a more corrosion
resistance article). The average first white rust for the control
or comparison rivets was 538 hours.
[0070] The following Examples list each step of the Process that
was used to treat the rivets and the length of time for each
Process.
Example 6
[0071]
2 Process Time A. Pretreat - Soap and Water (Clean) 1.0 Min. Rinse
(3X) 10 Sec/Each B. Activate - .01% Sulfuric Acid 30 Sec Rinse (3X)
10 Sec/Each C. Blacken - 12 g/l Ammonium Molybdate 45 Min 5 m/l
Ammonia D. Dry - Spin Dry E. Silicate Medium - 10% N Grade Sodium
Silicate Solution/D.I. Water @ 75.degree. C. pH 11.07, SG = 1.047
Electrify Medium with 7-9 Amp 15 Min. @ 15.7 Volts - Shut Off Power
Then Drop Workpiece Into Medium and Rotate Barrel 2 Min F. Drying -
None G. Topcoat - PPG Cathodic Black Lacquer
[0072] ASTM B-117 Performance: First White Rust 864 hours
Example 7
[0073]
3 Process Time A. Pretreat - E-Kleen 148 Solution (500 ml) 30 Sec
@37.degree. C. Rinse (3X) 10 Sec/Each B. Activate - E-Kleen 154
Solution 30 Sec @ Ambient Rinse (3X) 10 Sec/Each C. Blacken -
Insta-Blak Z-360 5 Min Rinse 5 Min D. Silicate Medium - 10% N Grade
Sodium Silicate Solution/D.I. Water @ 75.degree. C. pH 11.07, SG =
1.047 Electrify Medium With 15 Min 7-9 Amp @ 15.7 Volts Shut Off
Power And Then Drop Workpiece into Medium Rotate Barrel 2 Min E.
Drying - 120.degree. C. 4 Min F. Topcoat - PPG Cathodic Black
Lacquer
[0074] ASTM B-117 Performance: First White Rust 504 hours
Example 8
[0075]
4 Process Time A. Pretreat - Soap and Water (Clean) 1.0 Min Rinse
(3X) 10 Sec/Each B. Activate - 1% Sulfuric Acid 30 Sec C. Blacken -
Anodize in NaOH (60 g/l 30 Min @ 35-40.degree. C. @ 1.2 Amps, 3
Volts D. Dry - Spin Dry 30 Sec E. Silicate Medium - 17.5% D Grade
Sodium Silicate Solution/D.I. Water @ 75.degree. C., pH 11.84,
Electrify Medium with 15 Min 1.1 Amps, 2 Volts Shut Off Power Drop
Work Piece Into Medium Rotate Barrel 2 Min F. Drying - 80.degree.
C. 4 Min G. Topcoat - P.P.G. Cathodic Black Lacquer
[0076] ASTM B-117 Performance: First White Rust 826 hours
Example 9
[0077]
5 Process Time A. Pretreat - Soap and Water (Clean) 1 Min Rinse
(3X) 10 Sec/Each B. Activate - 0.1% Sulfuric Acid 30 Sec Rinse (3X)
10 Sec/Each C. Blacken - 12 g/l Ammonium Molybdate 45 Sec And 5 ml
Ammonia D. Dry - Spin Dry 30 Sec E. Silicate Medium - 10% N Grade
Sodium Silicate/D.I. Water S.G. 1.044 Electrify Medium 15 Min @
75.degree. C., 7-8 Amp, 15.7 Volts Shut Off Power Drop Workpiece
Into Bath Rotate Barrel 2 Min F. Drying - 4 Min @ 120.degree. C. G.
Topcoat - P.P.G. Cathodic Black Lacquer
[0078] ASTM B-177 Performance: First White Rust 522 hours
Example 10
[0079]
6 Process Time A. Pretreat - Soap and Watr (Clean) 1 Min Rinse (3X)
10 Sec/Each B. Activate - 0.1% Sulfuric Acid 30 Sec Rinse (3X) 10
Sec/Each C. Blacken - Anodize in NaOH (60 g/l @ 30 Min
35-40.degree. C.) @ 1.2 Amps, 3 Volts D. Dry - Spin Dry 30 Sec E.
Silicate Medium - 10% N Grade Sodium Silicate/D.I. Water S.G.
1.044, Electrify Medium 15 Min @ 75.degree. C., 7-8 Amp, 15.7 Volts
Shut Off Power Drop Workpiece Into Medium Rotate Barrel. 2 Min F.
Dry - None G. Topcoat - P.P.G. Cathodic Black Lacquer
[0080] ASTM B-117 Performance: First White Rust 828 hours
[0081] Examples 6-10 illustrate that, in some cases, the instant
invention can be employed along with a blackening or darkening
pretreatment for improving the corrosion resistance of topcoated
articles as well as achieving a substantially uniform black with
one coat of lacquer
Example 11
[0082] Example 4 was repeated with the exception that the rivets
were exposed to a metal pretreatment prior to being introduced into
the silicate medium. The metal pretreatment comprised dipping the
rivets into a solution comprising sodium silicate, magnesium and
aluminum (e.g., available commercially as RP-90 from A-Brite
Company, Dallas, Tex.), and spin drying. The pretreated rivets were
then exposed to the silicate medium for a period of about 7.5
minutes while applying a cathodic current to rivets. The rivets
were dried, rinsed and dried in accordance with Example 4. The
corrosion resistance of the dried rivets was tested in accordance
with ASTM B-117 and achieved an average of 192 hours before the
first occurrence of white rust (zinc corrosion products).
Example 12
[0083] Example 11 was repeated with the exception that the metal
pretreatment was thickened by adding an aliphatic polymer with
carboxylic acid groups (CARBOPOL supplied by B.F. Goodrich), and
the electrolytic treatment in the silicate medium was for 3.5
minutes. The corrosion resistance of the dried rivets was tested in
accordance with ASTM B-117 and achieved an average of 234 hours
before the first occurrence of white rust (zinc corrosion
products).
Example 13
[0084] Example 11 was repeated with the exception that the metal
pretreatment comprised sodium aluminate, sodium hydroxide and water
(20 ml of 5 wt. % sodium hydroxide and 14 grams of sodium
aluminate), and the electrolytic treatment in the silicate medium
was for 3.5 minutes. The corrosion resistance of the dried rivets
was tested in accordance with ASTM B-117 and achieved an average of
373 hours before the first occurrence of white rust (zinc corrosion
products).
Example 14
[0085] In this Example, Example 4 was repeated with the exception
that the rivets were not pretreated/cleaned and were exposed to an
acidic post-treatment. Rivets were treated with the process of
Example 4 for a period of thirty (30) seconds, spun dry, rinsed in
deionized water and then immersed in each of the following dilute
acidic solutions: Citric acid (pH 2.2, 5 ml acid in 200 ml
deionized water), oxalic acid (pH 3.0, 5 ml oxalic acid and 200 ml
deionized water) and glacial acetic acid (pH 3.4, 5 ml glacial
acetic acid and 2 liters deionized water). The corrosion resistance
of the acid treated rivets was tested in accordance with ASTM B-117
and the following number of hours passed without the appearance of
white rust (zinc corrosion products): citric =72 hrs, oxalic =24
hrs and glacial acetic acid =72 hrs.
Example 15
[0086] This Example demonstrates using the inventive process as a
post-treatment for the electrolytic process described in the
aforementioned Cross Referenced Related Patents and Patent
Applications. The rivets of Example 4 were cleaned with soap and
water and then dipped in dilute nitric acid. The rivets were then
introduced into a silicate medium of Example 4 and a charge ranging
from 7 to 9 amps at 15.7 V was applied with the rivets
corresponding to the cathode. The current was disconnected and the
rivets were removed from the silicate medium, and then reintroduced
into the silicate medium for a period of 15 minutes (without
current being applied). The rivets were dried for 4 minutes at 80C,
rinsed in deionized water and dried again. The corrosion resistance
of the dried rivets was tested in accordance with ASTM B-117 and
achieved an average of 160 hours before the first occurrence of
white rust (zinc corrosion products).
Example 16
[0087] This Example demonstrates using a pretreatment and a
post-treatment for the inventive process. The rivets of Example 4
were cleaned in soap and water and rinsed three times in deionized
water. The rinsed rivets were then dipped three times in dilute
nitric acid and rinsed three times in deionized water. The rinsed
rivets were then pretreated by being immersed in sodium aluminate
(38% sodium aluminate liquid [supplied by UALCO],10;1 dilution with
deionized water). The pretreated rivets were then spun dry. The
dried rivets were then treated in accordance with Example 4 but
with a bath comprising sodium silicate having a 6:1 alkaline to
silicate ratio (D Grade sodium silicate from PQ Corporation). The
rivets were then spun dry for 2 minutes at a temperature of 120F.
The dried rivets were then immersed in a solution comprising
colloidal silica (10 wt. % Ludox CL). The rivets were then dried
for 2 minutes at a temperature of 120F. A secondary coating or
sealer comprising silicate (RP 90 supplied by A Brite) was applied
onto the dried rivets. The rivets were dried for 3 minutes at 65 C.
The corrosion resistance of the dried rivets was tested in
accordance with ASTM B-117 and achieved an average of 188 hours
before the first occurrence of white rust (zinc corrosion
products).
Example 17
[0088] This example demonstrates using a pretreatment prior to
exposure to a silicate bath of the instant invention. Rivets were
pretreated in accordance with the description set forth in
following Tables 1 and 2. The sodium silicate bath of Example 4 was
electrified prior to introducing the pretreated rivets. The
corrosion resistance of the rivets was tested in accordance with
ASTM B-117. The resistance of the rivets to white rust (zinc
corrosion products) is set forth in Table 1, and the resistance of
the rivets to the formation of red rust (underlying iron corrosion)
is set forth in Table 2.
7TABLE 1 ID Description Max Min Average Std. Dev CV Range SAMPLE 1
Group A1 Sodium Acetate, 0.001 wt % 72 48 60 12.8 0.21 24 48 Group
A2 Sodium Acetate, 0.5 wt % 96 24 48 22.2 0.46 72 48 Group A3
Sodium Acetate, 5.0 wt % 96 48 66 17.0 0.26 48 48 Group B1 Aluminum
Ammonium Sulfate, 0.001 wt % 72 48 51 8.5 0.17 24 48 Group B2
Aluminum Ammonium Sulfate, 0.5 wt % 48 24 42 11.1 0.26 24 48 Group
B3 Aluminum Ammonium Sulfate, 5.0 wt % 120 24 54 30.8 0.57 96 48
Group C1 Aluminum Phosphate, 0.001 wt % 72 24 51 20.0 0.39 48 48
Group C2 Aluminum Phosphate, 0.5 wt % 96 24 60 22.2 0.37 72 72
Group C3 Aluminum Phosphate, 5.0 wt % 144 48 78 33.3 0.43 96 48
Group D1 Aluminum Nitrate, 0.001 wt % 72 24 51 15.4 0.30 48 72
Group D2 Aluminum Nitrate, 0.5 wt % 72 24 33 17.9 0.54 48 24 Group
D3 Aluminum Nitrate, 5.0 wt % 48 24 33 12.4 0.38 24 24 Group E1
Aluminum Fluoride, 0.001 wt % 72 24 57 17.9 0.31 48 48 Group E2
Aluminum Fluoride, 0.5 wt % 48 24 42 11.1 0.26 24 48 Group E3
Aluminum Fluoride, 5.0 wt % 48 24 33 12.4 0.38 24 24 Group F1
Zn(a)/Pretreat/SP0.5/DRD Control for A-E 72 24 51 20.0 0.39 48 24
Group F2 Zn(a)/SP0.5/DRD Only 96 48 66 17.0 0.26 48 72 Group F3
Zinc Plate(a) Only Control 24 24 24 0.0 0.00 0 24 Group G1
Pretreat/0.001 wt % Al K Sulfate/Sp0.5 DRD 72 24 51 15.4 0.30 48 48
Group G2 Pretreat/0.5 wt % Al K Sulfate/Sp0.5 DRD 96 24 57 22.0
0.39 72 24 Group G3 Pretreat/5.0 wt % Al K Sulfate/Sp0.5 DRD 72 24
57 17.9 0.31 48 72 Group G4 Pretreat/SP0.5/D/5.0 wt % Al K
Sulfate/D 48 24 39 12.4 0.32 24 48 Group H1 Pretreat/0.001 wt % Al
Tartrate/SP0.5 DRD 48 24 39 12.4 0.32 24 48 Group H2 Pretreat/0.5
wt % Al Tartrate/SP0.5 DRD 72 24 45 15.4 0.34 48 48 Group H3
Pretreat/5.0 wt % Al Tartrate/SP0.5 DRD 48 24 30 11.1 0.37 24 24
Group I1 Pretreat/0.001 wt % NaNH4PO4/SP0.5 DRD 48 24 39 12.4 0.32
24 48 Group I2 Pretreat/0.5 wt % NaNH4PO4/SP0.5 DRD 72 24 48 18.1
0.38 48 24 Group I3 Pretreat/5.0 wt % NaNH4PO4/SP0.5 DRD 72 24 45
15.4 0.34 48 48 Group J1 Pretreat/0.001 wt % Na D Gluconate/SP0.5
DRD 72 24 48 12.8 0.27 48 24 Group J2 Pretreat/0.5 wt % Na D
Gluconate/SP0.5 DRD 72 24 48 18.1 0.38 48 48 Group J3 Pretreat/5.0
wt % Na D Gluconate/SP0.5 DRD 96 48 63 17.9 0.28 48 48 Group K1
Zn(a)/Pretreat/SP0.5 DRD 96 24 48 22.2 0.46 72 48 Group K2
Zn(b)/Pretreat/SP0.5 DRD Control For G-K 96 24 54 21.3 0.39 72 48
Group K3 Zn(b)SP 0.5 DRD only 144 48 72 38.5 0.53 96 48 Group K4
Zn(b) Zinc Plate Only 24 24 24 0.0 0.00 0 24 Group K5 SP 0.5 D/pH
3.4 Acetic Acid/D 72 48 51 8.5 0.17 24 48 ID SAMPLE 2 SAMPLE 3
SAMPLE 4 SAMPLE 5 SAMPLE 6 SAMPLE 7 SAMPLE 8 Group A1 72 48 48 72
72 72 48 Group A2 48 24 96 48 48 48 24 Group A3 48 48 96 72 72 72
72 Group B1 48 48 48 48 48 72 48 Group B2 24 48 48 48 48 48 24
Group B3 48 24 72 24 48 48 120 Group C1 48 72 72 24 24 48 72 Group
C2 96 48 24 72 72 48 48 Group C3 72 48 48 96 72 96 144 Group D1 48
24 48 48 48 48 72 Group D2 24 24 24 24 24 48 72 Group D3 24 24 24
24 48 48 48 Group E1 24 48 72 48 72 72 72 Group E2 48 48 48 48 48
24 24 Group E3 48 48 24 48 24 24 24 Group F1 24 48 72 48 72 48 72
Group F2 48 48 72 48 72 96 72 Group F3 24 24 24 24 24 24 24 Group
G1 48 48 72 24 48 48 72 Group G2 72 48 72 48 48 48 96 Group G3 72
48 72 24 72 48 48 Group G4 48 48 48 48 24 24 24 Group H1 48 24 48
48 48 24 24 Group H2 24 48 48 72 48 24 48 Group H3 24 48 24 24 24
48 24 Group I1 48 24 48 48 24 24 48 Group I2 48 48 24 48 48 24 24
Group I3 48 72 24 24 48 48 48 Group J1 48 48 72 48 48 48 48 Group
J2 24 48 72 24 72 48 48 Group J3 96 72 48 72 48 72 48 Group K1 48
96 24 24 48 48 48 Group K2 48 96 24 48 48 72 48 Group K3 48 48 72
48 120 144 48 Group K4 24 24 24 24 24 24 24 Group K5 48 48 48 48 48
48 72
[0089]
8TABLE 2 ID Description Max Min Average Range St. Dev. CV SAMPLE 1
Group A1 Sodium Acetate, 0.001 wt % 168 96 135 72.0 22.0 0.16 120
Group A2 Sodium Acetate, 0.5 wt % 168 120 135 48.0 22.0 0.16 120
Group A3 Sodium Acetate, 5.0 wt % 168 96 138 72.0 24.8 0.18 96
Group B1 Aluminum Ammonium Sulfate, 0.001 wt % 144 96 111 48.0 17.9
0.16 96 Group B2 Aluminum Ammonium Sulfate, 0.5 wt % 144 96 114
48.0 17.0 0.15 96 Group B3 Aluminum Ammonium Sulfate, 5.0 wt % 144
72 111 72.0 25.5 0.23 72 Group C1 Aluminum Phosphate, 0.001 wt %
144 96 126 48.0 21.3 0.17 120 Group C2 Aluminum Phosphate, 0.5 wt %
144 120 123 24.0 8.5 0.07 120 Group C3 Aluminum Phosphate, 5.0 wt %
168 96 132 72.0 25.7 0.19 96 Group D1 Aluminum Nitrate, 0.001 wt %
168 120 135 48.0 17.9 0.13 120 Group D2 Aluminum Nitrate, 0.5 wt %
144 96 108 48.0 18.1 0.17 96 Group D3 Aluminum Nitrate, 5.0 wt %
144 96 114 48.0 17.0 0.15 96 Group E1 Aluminum Fluoride, 0.001 wt %
144 120 123 24.0 8.5 0.07 120 Group E2 Aluminum Fluoride, 0.5 wt %
144 96 111 48.0 17.9 0.16 120 Group E3 Aluminum Fluoride, 5.0 wt %
120 96 108 24.0 12.8 0.12 96 Group F1 Zn(a)/Pretreat/SP0.5/DRD
Control for A-E 144 120 129 48.0 12.4 0.10 120 Group F2
Zn(a)/SP0.5/DRD Only 168 144 153 24.0 12.4 0.08 144 Group F3 Zinc
Plate(a) Only Control 72 48 60 24.0 12.8 0.21 48 Group G1
Pretreat/0.001 wt % Al K Sulfate/Sp0.5 DRD 216 168 192 48.0 12.8
0.07 192 Group G2 Pretreat/0.5 wt % Al K Sulfate/Sp0.5 DRD 216 168
198 48.0 17.0 0.09 168 Group G3 Pretreat/5.0 wt % Al K
Sulfate/Sp0.5 DRD 240 168 195 72.0 27.0 0.14 240 Group G4
Pretreat/SP0.5/D/5.0 wt % Al K Sulfate/D 216 168 189 48.0 20.0 0.11
168 Group H1 Pretreat/0.001 wt % Al Tartrate/SP0.5 DRD 168 96 126
72.0 28.0 0.22 168 Group H2 Pretreat/0.5 wt % Al Tartrate/SP0.5 DRD
240 168 189 72.0 23.8 0.13 192 Group H3 Pretreat/5.0 wt % Al
Tartrate/SP0.5 DRD 216 120 177 96.0 33.8 0.19 168 Group I1
Pretreat/0.001 wt % NaNH4PO4/SP0.5 DRD 216 144 180 72.0 22.2 0.12
216 Group I2 Pretreat/0.5 wt % NaNH4PO4/SP0.5 DRD 216 168 198 48.0
17.0 0.09 216 Group I3 Pretreat/5.0 wt % NaNH4PO4/SP0.5 DRD 192 168
180 24.0 12.8 0.07 192 Group J1 Pretreat/0.001 wt % Na D
Gluconate/SP0.5 DRD 192 144 165 48.0 20.0 0.12 192 Group J2
Pretreat/0.5 wt % Na D Gluconate/SP0.5 DRD 216 168 198 48.0 17.0
0.09 216 Group J3 Pretreat/5.0 wt % Na D Gluconate/SP0.5 DRD 264
192 219 72.0 23.8 0.11 192 Group K1 Zn(a)/Pretreat//SP0.5 DRD 216
120 156 96.0 28.7 0.18 144 Group K2 Zn(b)/Pretreat//SP0.5 DRD
Control For G-K 240 192 222 48.0 24.8 0.11 192 Group K3 Zn(b)SP 0.5
DRD only 288 168 219 120.0 39.4 0.18 216 Group K4 Zn(b) Zinc Plate
Only 144 96 123 48.0 15.4 0.13 120 Group K5 SP 0.5 D/pH 3.4 Acetic
Acid/D 216 168 201 48.0 17.9 0.09 216 ID SAMPLE 2 SAMPLE 3 SAMPLE 4
SAMPLE 5 SAMPLE 6 SAMPLE 7 SAMPLE 8 Group A1 144 96 120 144 144 168
144 Group A2 120 120 168 144 120 168 120 Group A3 120 120 168 144
144 144 168 Group B1 96 96 120 120 96 144 120 Group B2 96 120 120
144 120 120 96 Group B3 96 96 120 96 120 144 144 Group C1 96 144
144 96 144 120 144 Group C2 120 120 120 120 144 120 120 Group C3
120 120 120 144 120 168 168 Group D1 120 120 168 144 120 144 144
Group D2 96 120 96 96 96 120 144 Group D3 96 96 120 120 120 120 144
Group E1 120 120 120 120 120 120 144 Group E2 120 120 96 96 96 96
144 Group E3 96 120 120 120 120 96 96 Group F1 120 120 144 120 144
120 144 Group F2 144 144 144 168 144 168 168 Group F3 72 48 72 72
48 48 72 Group G1 216 192 192 192 168 192 192 Group G2 192 192 216
216 216 192 192 Group G3 192 192 216 168 216 168 168 Group G4 216
192 192 192 168 168 216 Group H1 144 96 96 144 144 120 96 Group H2
192 168 168 240 192 168 192 Group H3 168 216 144 120 216 192 192
Group I1 192 168 168 192 168 144 192 Group I2 192 192 216 192 216
168 192 Group I3 192 192 168 168 168 168 192 Group J1 168 144 144
168 144 168 192 Group J2 192 192 216 192 216 168 192 Group J3 264
216 216 240 216 216 192 Group K1 144 216 120 168 168 144 144 Group
K2 240 240 240 240 192 240 192 Group K3 216 192 216 192 264 288 168
Group K4 144 96 144 120 120 120 120 Group K5 168 216 216 192 216
192 192
[0090] While the apparatus, compositions and methods of this
invention have been described herein, it will be apparent to those
of skill in the art that variations may be applied to the process
described herein without departing from the concept and scope of
the invention. All such similar substitutes and modifications
apparent to those skilled in the art are deemed to be within the
scope and concept of the invention and the appended claims.
* * * * *