U.S. patent application number 11/509966 was filed with the patent office on 2008-02-28 for metal coating process and product.
Invention is credited to Frederick G. Grawunde, Surry D. McFaul.
Application Number | 20080050608 11/509966 |
Document ID | / |
Family ID | 39113823 |
Filed Date | 2008-02-28 |
United States Patent
Application |
20080050608 |
Kind Code |
A1 |
McFaul; Surry D. ; et
al. |
February 28, 2008 |
Metal coating process and product
Abstract
A process for coating a metal part with a magnetron-sputtered
material to provide corrosion protection. The process results in a
part having a uniform coating. Coating materials include corrosion
resistant zinc with various options for appearances and levels or
corrosion protection.
Inventors: |
McFaul; Surry D.; (Sarasota,
FL) ; Grawunde; Frederick G.; (Sarasota, FL) |
Correspondence
Address: |
SHUMAKER LOOP & KENDRICK
101 E. KENNEDY, SUITE 2800
TAMPA
FL
33672-0609
US
|
Family ID: |
39113823 |
Appl. No.: |
11/509966 |
Filed: |
August 25, 2006 |
Current U.S.
Class: |
428/586 |
Current CPC
Class: |
F05D 2300/1616 20130101;
Y10T 428/12292 20150115; C23C 14/165 20130101; F01D 5/288 20130101;
C23F 13/08 20130101; Y10T 428/12799 20150115; C23C 14/021
20130101 |
Class at
Publication: |
428/586 |
International
Class: |
F01D 5/18 20060101
F01D005/18 |
Claims
1. A process for coating a metal part, the process comprising the
steps of: a) washing the metal part; b) rinsing the metal part; c)
inserting the metal part in a magnetron sputtering device; and d)
sputtering the metal part with a uniform layer of a sacrificial
target material.
2. The process of claim 1, wherein the washing step a) comprises
washing the metal part with heated water; and the rinsing step b)
comprises rinsing the metal part using heated, filtered water.
3. The process of claim 2, further comprising the steps of:
filtering the water in the rinsing step b) by reverse osmosis, and
heating the water in the washing step and the rinsing step to a
temperature between 100 degrees and 200 degrees Fahrenheit.
4. The process of claim 1, further comprising the steps of: e)
bathing the metal part in a passivate solution; and f) rinsing the
metal part in water after bathing step e).
5. The process of claim 4, wherein the inserting step c) further
comprises the step of: bombarding the metal part with ions, thereby
etching the metal part and removing contaminants from the metal
part.
6. The process of claim 5, further comprising the step of cooling
the metal part before the inserting step c).
7. The process of claim 5, further comprising the step of: g)
coating the metal part with a rust inhibitor.
8. The process of claim 7, wherein the sacrificial target material
comprises Aluminum.
9. The process of claim 8, wherein the sacrificial target material
comprises Zinc.
10. The process of claim 1, wherein the sacrificial target material
comprises Zinc and Aluminum.
11. The process of claim 1, wherein the metal part is comprised of
a mild steel and the sacrificial target material is comprised of
Zinc.
12. A metal part comprising a surface treated in accordance with
the process of claim 11.
13. The metal part of claim 12, wherein the metal part is a
cylindrical valve body.
14. A process for coating a metal part, the process comprising the
steps of: a) washing the metal part with water having a temperature
greater than 100 degrees Fahrenheit and a detergent; b) rinsing the
metal part with filtered water having a temperature greater than
120 degrees Fahrenheit in a first cascade bath; c) drying the metal
part with a stream of heated gas; d) cooling the metal part to a
temperature between 60 and 70 degrees Fahrenheit; e) inserting the
metal part in a magnetron sputtering device; f) ionizing glow
cleaning the metal part; g) sputtering the metal part with a first
layer of a target material comprising Zinc; h) applying a trivalent
chromate to the metal part; i) coating the metal part with a
sealer; and j) coating the metal part with a rust inhibitor.
15. A metal part comprising a surface treated in accordance with
the process of claim 14.
16. The metal part of claim 15, wherein the metal part is formed
from mild steel.
17. A cylindrical valve having an interior portion and an exterior
portion, the cylindrical valve comprising: a sacrificial material
being sputtered on the exterior portion, wherein the sacrificial
alloy has a uniform thickness.
18. The cylindrical valve of claim 17, further comprising: a
threaded region disposed on the exterior surface, the threaded
surface having a sacrificial material disposed thereon, wherein the
sacrificial material has a uniform thickness.
19. The cylindrical valve of claim 18, wherein the sacrificial
material comprises an alloy.
20. The cylindrical valve of claim 19, wherein the alloy comprises
Zinc.
21. The cylindrical valve of claim 19, wherein the cylindrical
valve is formed from a mild steel.
22. The cylindrical valve of claim 21, wherein the exterior portion
has a lustrous finish.
23. The cylindrical valve of claim 21, wherein the exterior portion
has a matte finish.
24. The cylindrical valve of claim 21, wherein the exterior portion
has a grey finish.
25. The cylindrical valve of claim 21, wherein the exterior portion
has a blue finish.
26. The cylindrical valve of claim 19, wherein the sacrificial
alloy comprises Zinc and Aluminum.
27. The cylindrical valve of claim 26, wherein the surface of the
interior portion and the exterior portion further comprises a rust
inhibitor.
28. The cylindrical valve of claim 27, wherein the surface of the
valve further comprises a sealer.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] This invention relates to coating metals.
[0003] 2. Background Information
[0004] Numerous uses of metal components or parts require coating
or plating a metal substrate with a separate material to provide an
end product with a desired characteristic. One such characteristic
is corrosion resistance. Galvanizing or chrome electroplating, for
example, renders metal parts significantly more corrosion resistant
than the substrate material.
[0005] Conventional forms of plating, however, have numerous known
drawbacks. In electroplating, for example, a substrate or part is
placed into a series electrically charged baths and dips. The baths
and dips require using chemicals such as solvents, volatile
organics, and/or other hazardous materials. For example, one
chemical commonly used in electroplating is cyanide. Such chemicals
can be harmful to workers that are exposed to them, harmful to the
environment, and expensive to dispose of, among other things.
Moreover, since electroplating requires good ventilation, it is
often performed in non-heated and non-cooled buildings, thus
creating difficult working conditions.
[0006] Additionally, conventional forms of electroplating
frequently result in non-uniform thickness of the plating. In
actuality, the thickness in electroplating can vary by as much as
five times the specified coating thickness due to low and high
current density zones on a single part. Parts with too much plating
can result in excessively thick threads. Excessively thick threads,
in turn, can result in parts that do not fit together properly or
obstruct the mechanics of the part, especially in applications
involving very tight tolerances. On the other hand, when the
plating is too thin or spotty, then the desired corrosion
resistance is not achieved. In either case, the plated part is
unusable and must be either re-plated (if possible) or otherwise
recycled (if possible).
BRIEF SUMMARY
[0007] The foregoing problems are solved and a technical advance is
achieved in an illustrative process for coating a metal part, a
part created using that process, or a corrosion resistant
cylindrical valve.
[0008] According to one aspect of the present invention, the
process provides an environmentally sound alternative to
conventional electroplating. That is, according to one aspect of
the present invention, the process utilizes environmentally
friendly materials, thereby sharply reducing--or entirely
eliminating--costs associated with using hazardous materials. Since
non-hazardous materials are used, the process can be performed in
climate-controlled buildings. Moreover, according to one aspect of
the present invention, this process also provides coating that is
thinner and significantly more uniform in thickness than
electroplated coatings, while having equal or improved corrosion
resistance relative to electroplated coatings. In one embodiment of
the present invention, a thin, uniform, protective coating is
provided as a solution to the problem of protecting metal parts
from corrosion without affecting critical dimensions of the metal
parts.
[0009] In another aspect of the present invention, the process
includes a number of steps for coating a metal part. In particular,
the process involves cleaning the metal part to remove oil residues
and other pollutants on the metal part. The cleaning is performed
with heated water and a detergent, or, alternatively, a solvent. If
the part is cleaned with water and an aqueous detergent, it is
rinsed in one or more cascade baths using heated, filtered water.
The metal part is then dried with an air knife and cooled to a
predetermined temperature. Once cooled, the metal part is subjected
to Plasma Vapor Deposition ("PVD") or more specifically
"sputtering." The PVD process deposits one layer of corrosion
resistant material on the metal part. After the PVD process, the
metal part is bathed in a passivate solution and a rust inhibitor
solution, then dried.
[0010] In another aspect of the present invention, a metal part is
provided having a surface treated in accordance with a process for
coating the metal part.
[0011] In yet another aspect of the present invention, a metal part
such as a cylindrical valve body having corrosion resistance to
environmental exposure is provided. The cylindrical valve includes
an interior portion, as well as an exterior portion having a
threaded region and a hexagonal region. The cylindrical valve body
is provided with a layer of corrosion resistant material formed
from a sacrificial metal such as a zinc alloy. The corrosion
resistant material is provided with a uniform thickness and is
isotropically disposed on the exterior portion of the cylindrical
valve. This coated valve further has a number of finishes,
including different colors and levels of luster.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 illustrates one embodiment of a process for coating a
metal part;
[0013] FIG. 2 illustrates one embodiment a first side view of a
magnetron sputtering device;
[0014] FIG. 3 illustrates a second side view of one embodiment of a
magnetron sputtering device;
[0015] FIG. 4 illustrates a perspective side view of a cross
section of a valve having a corrosion resistant surface;
[0016] FIG. 5 illustrates a scanning electron micrograph at 5,000
times magnification of a cross section of a steel substrate
conventionally plated with zinc;
[0017] FIG. 6 illustrates a scanning electron micrograph at 5,000
times magnification of a cross section of steel substrate sputter
coated with zinc;
[0018] FIG. 7 illustrates a micrograph at 116 times magnification
of a cross section of a steel crest of a thread conventionally
plated with zinc;
[0019] FIG. 8 illustrates a micrograph at 116 times magnification
of a cross section of a steel crest of a thread sputter coated with
zinc;
[0020] FIG. 9 illustrates a micrograph at 575 times magnification
of the upper left corner of the thread crest of FIG. 7; and
[0021] FIG. 10 illustrates a micrograph at 575 times magnification
of the upper left corner of the thread crest of FIG. 8.
DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERRED
EMBODIMENTS
[0022] The invention is described with reference to the drawings in
which like elements are referred to by like numerals. The
relationship and functioning of the various elements of this
invention are better understood by the following detailed
description. However, the embodiments of this invention as
described below are by way of example only, and the invention is
not limited to the embodiments illustrated in the drawings. It
should also be understood that the drawings are not to scale and in
certain instances details have been omitted, which are not
necessary for an understanding of the present invention, such as
conventional details of fabrication and assembly.
[0023] In general, FIG. 1 illustrates a method 10 of coating a
metal substrate or part such as a valve with a sacrificial alloy to
prevent or reduce corrosion of the substrate material. The method
generally involves washing and rinsing the part to remove
contaminants or detergent residues from the part. Once washed and
rinsed, the part is dried and cooled in preparation for the PVD
step. When dry and cool, the part is loaded into a magnetron
sputtering device, pumped down to high vacuum, and subjected to
additional cleaning. Once fully cleaned, the parts are sputtered
with a sacrificial alloy. After the sputtering step, the parts are
subjected to a post-sputtering process to further increase the
corrosion resistance of the parts. This is accomplished by applying
a passivate solution to the sputtered parts. The sputter process
mainly coats surfaces that are in the line-of-sight of the metal
atoms in the plasma. As a result, portions of the part not in the
line-of-sight will not be coated. For example, interior surfaces of
a cylindrical part are not in the line-of-sight of the metal atoms
in the plasma and thus are not coated during sputtering. These
areas can be temporarily protected from corrosion by applying a
rust inhibitor after the passivate step. The rust inhibitor is then
allowed to dry.
[0024] As illustrated in FIG. 1, the part is first subjected to a
pre-wash step 14. In particular, the part can be placed into a
commercial washing machine, such as a Hobart style washing machine.
The part is pre-washed by the Hobart machine with a detergent. One
environmentally friendly, suitable detergent is commercially
available as SIM Clean 101. Next, the part is washed in an
ultrasonic bath of 5% SimClean 101 and water. In one embodiment,
the part is preferably washed with water subjected to reverse
osmosis ("RO") filtration and heated to about 160 degrees
Fahrenheit. The wash cycle of step 16 is preferably about 2 minutes
in duration, although different durations may also produce
acceptable results. As used herein, the term "wash" is defined
broadly as cleansing using water, a solvent and/or another suitable
fluid. Moreover, wash is defined to include cleansing by an
ultrasonic bath.
[0025] Once the part is washed as detailed above, in steps 18 and
20 it is subjected to a rinse in a series of RO water baths to
further remove any oils or contaminants, in addition to any
remaining detergent residue from the pre-wash step 14-16. Heated RO
water is added to the baths so as to create a cascading flow of RO
water over the baffles of the bath tubs. The cascading flow of
heated RO water thus carries away remaining oils, contaminants and
detergent residues. The heated RO water can be approximately 160
degrees Fahrenheit. The part is subjected to each rinse bath for a
period of approximately 10-15 seconds, although different durations
may also produce acceptable results.
[0026] Instead of an aqueous wash, a solvent solution can be used
in the washing step. Exemplary solvents suitable for washing the
metal part(s) include petroleum based solvents, or other suitable
solvents, which will become apparent to one of ordinary skill in
the art in view of the present disclosure.
[0027] After the part is rinsed as described in steps 18 and 20, it
is dried in step 26. A number of various drying apparatuses can be
used to dry the part. For example, a series of air spouts arranged
as an air knife can be used. In such an embodiment, high pressure
air heated to 180 degrees Fahrenheit is directed onto the part for
approximately one minute. This high velocity, concentrated air
effectively sheets water off of the part. In addition, if the part
is not completely dry using the air knife, it can be further blown
off manually with a high pressure air hose. At this time, any
interior portions of the part that are still wet can also be
dried.
[0028] The dried part is then cooled in step 30 in preparation for
the PVD step. It has been discovered that the temperature of the
part during PVD is related to the luster, shine, or brightness of
the end product. In particular, when the part is at approximately
65-75 degrees Fahrenheit, the sputtered part is lustrous, shiny,
and bright. In contrast, when a part is sputtered at higher
temperatures, for example over 150 degrees Fahrenheit, the part
receives a dull or matte finish and darker in color. A number of
different colors can be achieved, depending on the temperature, the
gas environment in which parts are sputtered, and the type of
passivate. For example, parts can be made into colors such as olive
green, yellow, black, or even clear with respect to the substrate
material.
[0029] When the part is sufficiently cooled as described in step
30, it is ready for magnetron sputtering according to step 34. One
exemplary magnetron sputtering device is depicted in FIG. 2 and is
described in detail below. The part is placed onto a rack and
subsequently loaded into vacuum chamber 58 by electric cylinder
lift station 70 (FIG. 2). The vacuum chamber 58 is then sealed and
evacuated in step 37 to approximately 6.times.10.sup.-5 Torr using
a series of vacuum pumps, which are described in greater detail
below.
[0030] After the chamber is properly evacuated, the part is ready
to be ion glow discharge cleaned--or "glow cleaned"--as shown in
step 35. Glow cleaning improves the adhesion of the coated material
to the substrate. In particular, the glow clean process is
accomplished by exposing the part to a ion plasma field within the
vacuum chamber 58. This plasma field is formed by inputting a high
voltage direct current into an in-chamber high voltage electrode.
As the ions flow to the chamber walls, they bombard and
microscopically etch the part, which is in their path, thereby
removing remaining impurities from the part.
[0031] More specifically, to glow clean the part, the pallet
containing the part and the part are electrically charged, thus
creating a voltage drop between the part and the chamber. Argon gas
(or any other similar inert gas) is then introduced into the
chamber. The Argon gas is quickly ionized and is thus strongly
attracted to the chamber walls. The charged part is thus bombarded
by the Argon gas ions, which microscopically etch the part clean.
The part can be subjected to the glow clean step 35 for
approximately 5 seconds. Other ways of performing a glow clean step
will become apparent to those of ordinary skill in the art in view
of the present disclosure.
[0032] After the glow clean step 35, the part is sputtered in step
39. To sputter the part, combined electric and magnetic fields are
created by the hollow cathode direct current magnetron sputtering
source 66 (FIG. 2) to establish a large voltage differential (about
700 volts). The hollow cathode magnetron sputtering source 66 then
excites the target alloy atoms and dislodges them from the target
alloy 72. The Argon ions and the voltage differential then drives
the target alloy atoms into a plasma field surrounding the part,
thereby sputtering the part. The part is sputtered for
approximately 150 seconds, although different durations may be used
depending on the size of the magnetron sputtering device, the
desired thickness of the sputter coating, power supply, the partial
pressure of the Argon, the size of the target, and the distance
between the part to be sputtered and the target. It should be noted
that the part subjected to this embodiment of the present invention
results in a light grey to black finish. Alternatively, other inert
gases such as Nitrogen can be used to achieve a blue finish.
[0033] Once the part is sputtered in step 39, it is removed from
the magnetron sputtering device and subjected to a post-sputtering
treatment. Specifically, in step 36, a top coat is applied to the
part. The top coat is preferably a passivate solution such as a
trivalent chromate. A Trivalent chromate is commercially available
under the trade name SurTec 667. The passivate solution can be
combined with a sealer such as SurTec 551. Both the passivate and
the sealer are commercially available through CST-SurTec. As used
herein, the term "applied" is defined broadly, meaning to bring
into contact with, e.g., to bath, dip, either fully or partially,
or spray.
[0034] The part is then rinsed using RO water, as shown in step 40.
Once rinsed, the part is bathed in a 10% solution of rust inhibitor
in RO water, as shown in step 44. An exemplary rust inhibitor is
commercially available as SealProof 6151, which is available
through Innovative Chemical Solutions. The rust inhibitor provides
corrosion resistance for sections of the part that are not
sputtered, for example, interior portions. The part is then dried
in step 48, either by a fan, an air knife, or other drying method
that will become apparent to one of ordinary skill in the art in
view of the present disclosure.
[0035] FIG. 2 illustrates the magnetron sputtering device 100 of
one embodiment of the present invention. Sputtering device 100
includes sputtering vacuum chamber 58, a hollow cathode direct
current magnetron sputtering source 66, a target material 72, an
inert gas supply 67, and one or more evacuation pumps 60, 61, 62,
and 64.
[0036] Vacuum chamber 58 can be configured in a wide variety of
dimensions, depending on the size and quantity of the part(s) to be
sputtered. In one embodiment of the present invention, the vacuum
chamber 58 is 24 inches wide and 60 inches long and 17 inches high.
The vacuum chamber 58 can also be provided with an integral welded
tube frame. The vacuum chamber 58 further includes an electric or
pneumatic cylinder lift station 70. Lift station 70 can further be
outfitted with a rack to support the part(s) to be sputtered.
[0037] As further illustrated in FIG. 2, the vacuum chamber 58
houses a hollow cathode direct current magnetron sputtering source
66. For a vacuum chamber having the dimensions set forth above,
sputtering source 66 can be approximately 14 inches in diameter by
12 inches high. Sputtering source 66 can be powered by a panel
mounted 12 kilowatt direct current, alternating current, or radio
frequency magnetron power supply 68. Of course, as will be apparent
to a person of ordinary skill in the art in view of the present
disclosure, the sputtering source can be enlarged or reduced in
size depending on the size of the part or cluster of parts to be
sputtered. Likewise, instead of a hollow cathode sputtering source,
a planar magnetron could also be used.
[0038] As shown in FIG. 2, the vacuum chamber 58 further houses the
target material 72. To impart corrosion resistance on the part(s)
to be sputtered, a sacrificial metal or alloy target is preferably
used. Exemplary sacrificial metals include Zinc or Aluminum.
Exemplary sacrificial alloys include Zinc alloys such as Zinc and
Aluminum alloys. One particular alloy includes approximately 98%
Zinc and 2% Aluminum. Of course, Zinc-Aluminum alloys having larger
percentages of Aluminum could alternatively be used. The target
alloy 72 to be used with the vacuum chamber 58 and sputtering
source 66 described above can be of a cylindrical shape. In
particular, the dimensions of the cylindrical shape are
approximately 12.75 inches in diameter by 12 inches high by 0.375
inches thick. Alternatively, for a planar magnetron, a target
having dimensions of approximately 5 inches by 30 inches can be
used.
[0039] The inert gas supply 67 provides inert gas, for example
Argon, to be ionized in the vacuum chamber 58. The inert gas supply
67 preferably includes a storage cylinder in which the inert gas
can be stored. An alternative gas that can be used is Nitrogen.
Such a gas results in parts having a blue finish, as mentioned
above.
[0040] Referring to FIG. 2, the sputtering device 100 includes one
or more evacuation pumps. The evacuation pumps are configured to
evacuate the vacuum chamber as detailed above. In particular, one
embodiment of the magnetron sputtering device 100 includes a BOC
Edwards 412J-014 mechanical pump and 900-615-MV15 blower 60, a
Varian HS-16 diffusion pump 61, and a CT-10 Cryo-Pump 62 & 64.
In combination, these pumps evacuate the vacuum chamber 58 to
better than approximately 6.times.10.sup.-5 Torr.
[0041] In an alternative embodiment, a turbo pump could be used
and/or a load lock system. A load lock configuration allows for the
sputter chamber to remain constantly under vacuum, thereby allowing
near constant sputtering of parts. That is, by maintaining a
constantly evacuated vacuum chamber, a load lock system obviates
the need to repeatedly evacuate the sputter chamber in between
sputtering cycles.
[0042] A wide variety of magnetron sputtering variations will
become apparent to one of ordinary skill in the art in view of the
present disclosure. Such variations are thus considered to be
within the scope of the present invention as defined by the claims.
For Example, the use of a higher volume Magnetron sputtering device
will be apparent to one of ordinary skill in the art in view of the
present disclosure.
[0043] Referring now to FIG. 3, a sputter coated valve 200 is
illustrated according to one aspect of the present invention. In
particular, sputter coated valve 200 includes an interior portion
214 and an exterior portion 218. The exterior portion 218 has a
hexagonal portion 222 for tightening or loosening the valve. The
exterior portion 218 is provided with a corrosion resistant coating
230 using the process detailed above. One exemplary coating is a
Zinc alloy as described in greater detail above. Coating 230 is
relatively uniformly applied to exterior portion 218, including the
hexagonal portion 222 and male thread 226. As a result of the
uniformity and thickness of coating 230, the desired corrosion
resistance is achieved without obstructing the mechanics of the
valve. In addition, sputter coated valve 200 is provided with a
rust preventative 234 covering both the interior portion 214 and
the exterior portion 218. Valve 200 can be formed from a wide
variety of materials such as mild steel or other alloys.
[0044] FIGS. 5, 7, and 9 illustrate steel substrates plated using
conventional electroplating techniques. FIGS. 7 and 9 show the
substantial thickness and non-uniform structure of conventionally
plated zinc 7 relative to a steel substrate 8. FIG. 9, in
particular, shows the substantial build-up of plated zinc 7 that
occurs at the edges of a thread crest. Such build-up alters the
dimensions of plated parts, thereby rendering them often unusable,
as discussed above.
[0045] FIGS. 6, 8, and 10, illustrate a steel substrate
sputter-coated with zinc using the process of FIG. 1. In
particular, FIGS. 6, 8, and 10 illustrate the substantially thin
and uniform structure of sputtered zinc 11 relative to steel
substrate 8. Additionally, FIGS. 6, 8, and 10 lack the undesirable
build-up seen in conventionally plated steel parts.
[0046] It is therefore intended that the foregoing detailed
description be regarded as illustrative rather than limiting, and
that it be understood that it is the following claims, including
all equivalents, that are intended to define the spirit and scope
of this invention.
* * * * *