CONVERSION COATINGS WITH CONDUCTIVE ADDITIVES,
PROCESSES FOR APPLYING SAME AND THEIR COATED ARTICLES
FIELD OF THE INVENTION
[0001] The invention relates to conversion coatings and, more
particularly, relates to conversion coatings with conductive
additives.
BACKGROUND OF THE INVENTION
[0002] Aluminum alloy conversion coatings provide a combination
of corrosion inhibition and apparent surface electrical
conductivity. Current state-of-the art trivalent chromium
conversion coatings do not demonstrate stable surface
conductivity. Evidence exists that hexavalent chromate
conversion coatings do not impart true electronic conductivity,
but provide metal-to-metal contact due to localized failure of
the passive film under load. The superb corrosion inhibition
and passive film "self repair" provided by chromate conversion
coatings permits them to be used in applications where surface
conductivity is required. Due to their carcinogenic properties,
however, hexavalent chromium coatings are heavily regulated and
are thus to be avoided whenever possible.
SUMMARY OF THE INVENTION
[0003] In accordance with yet another aspect of the present
invention, a coating composition broadly comprises a conductive
polymer including at least one of the following: a single
conductive polymer, a dual strand conductive polymer, a
combination of a single conductive polymer and a dual strand
conductive polymer or an organic-inorganic hybrid composite.

[0004] In accordance with yet another aspect of the present
disclosure, a process for coating an article broadly comprises
contacting an aluminum-based article with a solution, said
solution includes a solvent and a conductive polymer having at
least one of the following: a single conductive polymer, a dual
strand conductive polymer, a combination of a single conductive
polymer and a dual strand conductive polymer; and drying a
coated aluminum-based part or an organic-inorganic hybrid
composite.
[0005] In accordance with yet another aspect of the present
invention, a coated article broadly comprises an article
includes at least one surface having a coating disposed
thereupon, wherein said coating includes at least one conductive
polymer bonded to at least one intermetallic particle of said at
least one surface, wherein said at least one conductive polymer
includes at least one of the following: a single conductive
polymer, a dual strand conductive polymer, a combination of a
single conductive polymer and a dual strand conductive polymer
or an organic-inorganic hybrid composite.
[0006] The details of one or more embodiments of the invention
are set forth in the accompanying drawings and the description
below. Other features, objects, and advantages of the invention
will be apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a flowchart illustrating the steps of two
exemplary processes described herein;

[0008] FIG. 2 is a representation of an exemplary conductive
polymer embodying an organic-inorganic composite hybrid
containing an inorganic inhibitor species;
[0009] FIG. 3 is a representation of another exemplary
conductive polymer embodying an organic-inorganic composite
hybrid containing a film forming agent;
[0010] FIG. 4 is a representation of an exemplary coated article
made in accordance with exemplary process #1 of FIG. 1; and
[0011] FIG. 5 is a representation of another exemplary coated
article made in accordance with exemplary process #2 of FIG. 1.
[0012] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0013] Generally, it is widely recognized that aluminum-based
parts are not homogeneous throughout and contain intermetallic
particles such as copper, manganese, iron, silicon, zinc,
magnesium, chromium, titanium, and the like, depending upon the
type of alloy, as known to one of ordinary skill in the art.
Intermetallic particles exposed at the surface of an aluminum-
based part serve as active corrosion site(s). The exemplary
conversion coatings described herein contain a conductive phase
capable of binding directly to the exposed intermetallic
particles and preventing corrosion from occurring. An exemplary
conversion coating described herein may contain a non-conductive
phase and an electrically conductive phase. Generally, the non-

conductive phase may be a typical metal oxide or metal oxide
mixture, while the conductive phase may be a conductive polymer,
for example, a single conductive polymer or a dual strand
conductive polymer, combined with an inorganic inhibitor species
or a film forming agent. The conductive phase may bond to the
intermetallic particles and extend through a barrier phase to
the free surface of the coating.
[0014] As used herein, the terms "non-conductive phase" and
"non-conductive material" may include any one or more of the
following non-conductive materials: metal oxides; metal oxide
mixture; metal oxides of an alloy(s) of an article; and the
like. For example, representative metal oxides may include a
metal from the metalloids, also known as the "poor metals", of
the Periodic Table of Elements as shown in the Handbook of
Chemistry and Physics, CRC Press, 71st ed., p. 1-10 (1990-91),
such as aluminum, gallium, germanium, indium, tin, lead, boron,
silicon and bismuth, with aluminum oxides, indium oxides and tin
oxides being the most commonly utilized oxides as known to one
of ordinary skill in the art.
[0015] As used herein, the term "conductive polymer" means
either a single conductive polymer, a dual strand conductive
polymer, a combination of a single conductive polymer or a dual
conductive polymer or an organic-inorganic composite hybrid
composed of a conductive organic component and an inorganic
component, where the conductive organic component may comprise
an aforementioned conductive polymer inorganic component may
comprise an inorganic inhibitor species (See FIG. 2) or a film
forming agent (See FIG. 3). Suitable single conductive polymers
may include polyaniline, polyacetylene, polypyrrole,

polythiophene, poly(phenylene vinylene), and the like. Suitable
dual strand conductive polymers may include at least one of the
following polymers: polyaniline, polyacetylene, polypyrrole,
polythiophene, and poly(phenylene vinylene), bonded to a
polyanion, wherein the bond is not a covalent bond. The
conductive polymer may include at least one terminal end having
a coupling agent attached thereto.
[0016] As used herein, the term "coupling agent" means a
functional group bonded to the terminal end of a conductive
polymer. For example, the terminal end functional group of the
conductive polymer may include any one of the following: beta-
diketones, mercaptoesters, benzotriazoles, benzothiazoles,
amines, and carboxylic acids, combinations comprising at least
one of the foregoing, and the like. Generally, these functional
groups are recognized for their ability to enhance the adhesive
bond strength of thermoset resins to metallic substrates. The
resultant electrically conductive polymer film is covalently
bonded to the article's surface, and bonded at a relatively high
density to intermetallic particles on the article's surface.
When employing conductive polymers having such functional
groups, the molecular geometry of the conductive polymers may be
branched or dendritic.
[0017] As used herein, the term "inorganic inhibitor species"
means a selective inhibitor species that precipitates a layer of
non-conductive material (Inh- shown in FIG. 2) upon a surface of
an active corrosion site. Inorganic inhibitor species are
generally known for their inhibitive and/or self-healing
properties as known to one of ordinary skill in the art.
Suitable inorganic inhibitor species for use herein are

described and disclosed in U.S.P.N. 6,537,678 to Putnam et al.,
which is incorporated by reference herein in its entirety. For
example, inorganic inhibitor species may include metals of
Groups V, VI and the lanthanide series of metals of the
aforementioned Periodic Table of Elements as referenced above.
[0018] As used herein, the term "film forming agent" means a
selective agent that precipitates a non-conductive material (Ag-
shown in FIG. 3) to form a barrier film upon the entirety of a
surface. Suitable film forming agents for use herein may be
oxides of metals of Groups IV, V and VI of the aforementioned
Periodic Table of Elements as referenced above. For example,
some suitable film forming agents for use herein may be titanium
oxide, titanium dioxide, hafnium oxide, hafnium dioxide,
zirconium oxide, zirconium dioxide, and the like.
[0019] Referring nov; to FIG. 1, a representative flowchart
illustrating two exemplary processes described herein are shown.
Generally, process #1 may be utilized to form an exemplary
embodiment of a coated article (See FIG. 4) as well as serve as
precursor steps to performing process #2. Process #2 may be
utilized to form another exemplary embodiment of another coated
article (See FIG. 5). In preparation of being coated, an
article, e.g., an aluminum-based part, may optionally undergo
pretreatment at step 10, such as an abrasive cleaning technique,
e.g., deoxidizing, degreasing, and the like, followed by
optional rinsing and drying steps as known to one of ordinary
skill in the art. For example, one or more surfaces to be
coated may be abrasively treated. Afterwards, the abrasively,
cleaned article may be washed in a mild detergent, and then
rinsed with tap water, deionized water or ethanol as known to

one of ordinary skill in the art. In addition, a chemical etch
or deoxidizing surface treatment step followed by a water rinse
may also optionally be applied after washing in a mild detergent
as known to one of ordinary skill in the art.
[0020] After pretreating the article, the article may be
contacted at step 12 with a solution comprising a solvent, a
non-conductive material and a conductive polymer. As described
herein, the conductive polymer may have at least one coupling
agent bonded thereto or may be free of the coupling agent. In
an alternative embodiment, when the conductive polymer is free
of a coupling agent, the coupling agent may be added to the
solution such that the solvent, conductive polymer and at least
one coupling agent may combine to form an emulsion. Given the
various embodiments and alternatives, suitable solvents may
include any solvent that can dissolve the conductive polymer,
non-conductive material and the optional coupling agent.
[0021] Suitable contacting techniques may include immersion,
spraying, brushing, combinations comprising at least one of the
foregoing processes, and the like. When utilizing an emulsion,
one of ordinary skill in the art may adapt the contacting
technique as recognized in order to form the electrically
conductive material coating upon the surface of the article.
[0022] During the contacting process, the pH may fluctuate
throughout the process due to the sensitive nature of the
chemistries involved as known to one of ordinary skill in the
art. The solution may be monitored to maintain a pH range of
about 3.5 to about 10.5. The article may be immersed within the

solution for a period of time of about 1 minute to about 10
minutes to form the electrically conductive coating.
[0023] During step 12, the layer of non-conductive material
forms in situ, that is, a layer of a metal oxide, as a reaction
byproduct of the contacting processes described above. When an
organic-inorganic hybrid composite is not utilized as the
conductive polymer, the non-conductive material of the solution
or emulsion serves as the starting material for the resultant
non-conductive material layer. When an organic-inorganic hybrid
composite is utilized as the conductive polymer, the inorganic
inhibitor species or film forming agent provide the starting
material for the resultant non-conductive material layer. In
the meantime, the conductive polymer, with or without the use of
a coupling agent, binds to the intermetallic particles present
in the article's surface. As recognized by one of ordinary
skill in the art, the conductive polymer is in the form of
strands such that at least one terminal end binds to an
intermetallic particle while at least one other terminal end
remains unattached. The unattached terminal end is able to
settle at or proximate to the surface of the layer of metal
oxide, or non-conductive material layer, in order to form and
act as an electrically conductive conduit between the surface of
the non-conductive material layer and the article's surface.
[0024] After coating the article at step 14, the coated article
may be rinsed at step 16 using any one of a number of techniques
known to one of ordinary skill in the art and dried at step 18.
Suitable drying techniques include conventional, techniques such
as by air, heating element, infrared element, combinations
comprising at least one of the foregoing, and the like, as known

to one of ordinary skill in the art. For example, the coated
article may be dried at a temperature of about 25°C (77°F) to
about 125°C (257°F) for a period of time of about 0.5 to about
24 hours.
[0025] Referring now to FIG. 4, a resultant coated article 30 of
process #1 may comprise at least one surface 32 having disposed
thereupon a non-conductive material layer 34 containing a
plurality of electrically conductive polymer strands 36. As
described above, the plurality of electrically conductive
polymer strands 36 may be bonded to a plurality of intermetallic
particles 37 present throughout the surface 32 and extending to
and proximate to a surface 38 of the non-conductive material
layer 34. The resulting non-conductive material layer 34 may
have a thickness of about 50 nanometers to about 1000
nanometers.
[0026] As described above, the coated article may undergo
further steps to form yet another exemplary embodiment of an
exemplary process, exemplary coating and exemplary coated
article described herein. The coated article of FIG. 2 may
again be contacted with a solution comprising a solvent and an
electrically conductive material, to form an electrically
conductive layer upon the non-conductive layer containing the
veined network of conductive polymer strands described above.
The electrically conductive material may include a coupling
agent or may be free of the coupling agent, such that the
coupling may instead be an additive included in the solution or
may not be included.

[0027] Suitable contacting processes may include immersion, air
spray, electrostatic deposition, brush application, flood
coating, chemical conversion, sol gel, cold spray, sputtering,
vapor deposition, combinations comprising at least one of the
foregoing, and the like, as known to one of ordinary skill in
the art.
[0028] For example, a sol gel overlay coating solution may be
prepared from a group IV metal based organic compound with the
addition of a conductive polymer in the presence or absence of
an alcohol, ketone, or similar solvents. For example, the group
IV metal may be aluminum and the compound may be an aluminum
isopropoxide compound. In this example, the gels are formed by
processing metal alkoxides, first hydrolyzing and then
polymerizing to form the gel as known to one of ordinary skill
in the art. The group IV metal may comprise approximately 0 to
approximately 90 weight % of the sol gel based upon the total
atom % of the sol gel. During preparation, the pH of the sol
gel is carefully controlled. Fracture of the non-conductive
coating layer may be prevented through the addition of one or
more chemical additives, such as surfactants, drying control
chemical additives, and the like, and other processing
techniques known to one of ordinary skill in the art. Once
prepared, the sol gel may undergo an optional rinsing step (not
shown) to thin the gel and displace any excess solvent present
as known to one of ordinary skill in the art. The aluminum
alloy articles may undergo a heat treatment at a temperature of
up to about 125°C (257°F) to fully evaporate the gel and form a
uniform coating. Heat treatment temperatures may be reduced by
careful replacement of water with alcohols and other volatile
solvents as known to one of ordinary skill in the art.

[0029] In the alternative, the overlay coating solution may be
formed through traditional polymerization techniques to form a
polymer gel with the entrapped conductive material and group IV
metal as known to one of ordinary skill in the art. In this
alternative example, multi-component oxides may be achieved by
dissolving hydrous oxides or alkoxides together with polyhydroxy
alcohol and a chelating agent. The introduction of this organic
polymer component to the inorganic sol gel will lead to more
flexible and functionalized films.
[0030] After coating the article at step 18, the coated article
may be optionally rinsed (not shown) using any one of a number
of techniques known to one of ordinary skill in the art and
dried at step 20. Suitable drying techniques include
conventional techniques such as by air, heating element,
infrared element, combinations comprising at least one of the
foregoing, and the like, as known to one of ordinary skill in
the art. For example, the coated article may be dried at a
temperature of about 25°C (77°F) to about 125°C (257°F) for a
period of time of about 0.5 to about 24 hours.
[0031] Referring now to FIG. 5, a resultant coated article 40 of
process #2 may have at least one surface 42 having disposed
thereupon a non-conductive material layer 44 containing the
aforementioned veined network of electrically conductive polymer
strands 46 whereupon an electrically conductive overlay coating
layer 48 may be disposed. As described above, the plurality of
electrically conductive polymer strands 4 6 may be bonded to a
plurality of intermetallic particles 47 present throughout the
surface 42 and extending to and proximate to a surface 50 of the
non-conductive material layer 44 and in contact with the

electrically conductive overlay coating layer 48. The resulting
electrically overlay coating layer 48 and non-conductive
material layer 44 may have a combined thickness of about 50
nanometers to about 5000 nanometers.
[0032] One or more embodiments of the present invention have
been described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. Accordingly, other embodiments are
within the scope of the following claims.


1. A coating composition, comprising:
a conductive polymer including at least one of the
following: a single conductive polymer, a dual strand conductive
polymer, a combination of a single conductive polymer and a dual
strand conductive polymer or an organic-inorganic hybrid
composite.
2. The coating composition of claim 1, wherein said conductive
polymer includes at least one terminal end having a coupling
agent bonded thereto.
3. The coating composition of claim 2, wherein said coupling
agent comprises any one of the following functional groups:
beta-diketones, mercaptoesters, benzotriazoles, benzothiazoles,
amines, and carboxylic acids.
4. The coating composition of claim 1, wherein said single
conductive polymer comprises at least one of the following:
polyaniline, polyacetylene, polypyrrole, polythiophene, and
poly(phenylene vinylene).
5. The coating composition of claim 1, wherein said dual
strand conductive polymer comprises a complex of at least one
polyanion and at least one of the following: polyaniline,
polyacetylene, polypyrrole, polythiophene, and poly(phenylene
vinylene).

6. The coating composition of claim 5, wherein said polyanion
comprises at least one of the following: polysulfonic acid (such
as poly(styrenesulfonic acid)) or polycarboxylic acids (such as
poly(acrylic acid) or poly(methyl-methacrylate)).
7. The coating composition of claim 1, wherein said conductive
polymer is free of a coupling agent.
8. The coating composition of claim 1, wherein said organic-
inorganic hybrid composite further comprises at least one
inorganic inhibitor species or at least one film forming agent.
9. The coating composition of claim 8, wherein said at least
one film forming agent comprises at least one of the following:
an oxide of a metal of Groups VI, V or VI.
10. The coating composition of claim 8, wherein said at least
one inorganic inhibitor species comprises at least one of the
following: a metal of Group V, VI or the lanthanide series.
11. A process for coating an article, comprising:
contacting an aluminum-based article with a solution, said
solution includes a solvent and a conductive polymer having at
least one of the following: a single conductive polymer, a dual
strand conductive polymer, a combination of a single conductive
polymer and a dual strand conductive polymer or an organic-
inorganic hybrid composite; and
drying a coated aluminum-based part.
12. The process of claim 11, further comprising the steps of:
contacting a dried coated aluminum-based part with a
solution to form an electrically conductive material layer upon

a non-conductive material layer of said dried coated aluminum-
based part, said solution includes a solvent and an electrically
conductive material; and
drying a coated aluminum based part.
13. The process of claim 11, wherein contacting comprises
contacting said aluminum-based article with a solution
maintained at a pH range of about 3.5 to about 10.5.
14. The process of claim 11, wherein contacting comprises any
one of the following processes: immersion, spraying or brushing.
15. The process of claim 11, wherein contacting comprises
contacting said aluminum-based article with said solution for a
period of time of about 1 minutes to about 10 minutes.
16. The process of claim 11, wherein contacting comprises
contacting said aluminum-based article with said solution, said
solution comprises an emulsion.
17. The process of claim 11, wherein said conductive polymer
includes at least one terminal end with a coupling agent bonded
thereto.
18. The process of claim 11, wherein contacting comprises
contacting said aluminum-based article with said solution, said
solution further comprises at least one of the following
inorganic inhibitor species: a metal of Groups V, VI or the
lanthanide series.
19. The process of claim 18, wherein contacting comprises
contacting said aluminum-based article with said solution, said

solution further comprises at least one of the following film
forming agents: an oxide of a metal of Groups IV, V or VI.
20. The process of claim 11, further comprising pretreating an
aluminum-based article to be coated prior to contacting said
aluminum-based article with said solution.
21. A coated article, comprising:
an article includes at least one surface having a coating
disposed thereupon,
wherein said coating includes at least one conductive
polymer bonded to at least one intermetallic particle of said at
least one surface,
wherein said at least one conductive polymer includes at
least one of the following: a single conductive polymer, a dual
strand conductive polymer, a combination of a single conductive
polymer and a dual strand conductive polymer or an organic-
inorganic hybrid composite.
22. The coated article of claim 21, wherein said single
conductive polymer comprises at least one of the following:
polyaniline, polyacetylene, polypyrrole, polythiophene, and
poly(phenylene vinylene).
23. The coated article of claim 22, wherein said dual strand
conductive polymer comprises a complex of at least one polyanion
and at least one of the following: polyaniline, polyacetylene,
polypyrrole, polythiophene, and poly(phenylene vinylene).
24. The coated article of claim 23, wherein said polyanion
comprises at least one of the following: polyacrylic acid,
polysulfonic acid (such as poly(styrenesulfonic acid)) or

polycarboxylic acids (such as poly(acrylic acid) or poly(methyl-
methacrylate)).
25. The coated article of claim 21, wherein said at least one
conductive polymer includes a terminal end having a coupling
agent bonded thereto.
26. The coated article of claim 25, wherein said coupling agent
includes at least one of the following functional groups: beta-
diketones, mercaptoesters, benzotriazoles, benzothiazoles,
amines, or carboxylic acids.
27. The coated article of claim 21, wherein said organic-
inorganic hybrid composite further comprises at least one
inorganic inhibitor species or at least one film forming agent.
28. The coated article of claim 27, wherein said at least one
inorganic inhibitor component comprises at least one of the
following: a metal of Groups V, VI or the lanthanide series.
29. The coated article of claim 27, wherein said at least one
film forming agent comprises at least one of the following: an
oxide of a metal of Groups IV, V or VI.
Dated this30th day of April, 2008.

A coating composition includes a conductive polymer
including at least one of the following: a single conductive
polymer, a dual strand conductive polymer, a combination of a
single conductive polymer and a dual strand conductive polymer
or an organic-inorganic hybrid composite.