U.S. patent application number 14/193174 was filed with the patent office on 2014-09-04 for apparatus and process for nickel plating and sealing.
The applicant listed for this patent is INTEGRATED PROTECTIVE COATINGS, INC.. Invention is credited to Robert FRANKE.
Application Number | 20140248432 14/193174 |
Document ID | / |
Family ID | 51421065 |
Filed Date | 2014-09-04 |
United States Patent
Application |
20140248432 |
Kind Code |
A1 |
FRANKE; Robert |
September 4, 2014 |
APPARATUS AND PROCESS FOR NICKEL PLATING AND SEALING
Abstract
A pre-treatment process surface preparation of workpieces for
subsequent nickel coating is provided including a thermal process
to remove residue, grit blasting for surface roughening, such as
with garnet, and rust avoidance by submergence in hot ammonia. Use
of expensive tank materials for electroless nickel coating are
avoided through the provision of replaceable liners optionally
protected from the subject workpieces using movable wall panels.
Further, tank heating is effectively provided using industrial hot
water heaters and an indirect water/nickel solution heat exchanger,
obviating the need for risky and regulated heat sources. In a final
option, a fluoropolymer sealer is provided over the nickel
coating.
Inventors: |
FRANKE; Robert; (Ardrossan,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTEGRATED PROTECTIVE COATINGS, INC. |
Edmonton |
|
CA |
|
|
Family ID: |
51421065 |
Appl. No.: |
14/193174 |
Filed: |
February 28, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61771171 |
Mar 1, 2013 |
|
|
|
Current U.S.
Class: |
427/299 ;
118/400; 118/428; 118/429; 134/7 |
Current CPC
Class: |
C23C 18/1617 20130101;
C23C 18/1619 20130101; C23C 18/1676 20130101; C23C 18/1834
20130101; C23C 18/1806 20130101; C23C 18/36 20130101; C23C 18/34
20130101; C23C 18/32 20130101 |
Class at
Publication: |
427/299 ;
118/428; 118/429; 118/400; 134/7 |
International
Class: |
C23C 2/04 20060101
C23C002/04; C23C 2/00 20060101 C23C002/00 |
Claims
1. A method for preparing a workpiece for plating comprising:
heat-soaking the workpiece for thermal removal of residue
therefrom; and blasting the residue-free workpiece with garnet
grit.
2. The method of claim 1 wherein the heat-soaking further comprises
heating the workpiece at about 400.degree. C. for about 8
hours.
3. The method of claim 1 wherein the garnet grit is about 120
mesh.
4. The method of claim 1 further comprising submerging the
workpiece in hot ammonia.
5. The method of claim 4 wherein the hot ammonia has a
concentration of about 0.06 to 0.10% in water.
6. The method of claim 5 wherein the workpiece is submerged in the
hot ammonia at temperatures of about 60.degree. C. to about
75.degree. C. for about 0.5 to about 1.5 hours.
7. The method of claim 1 wherein the workpiece is iron bearing.
8. A method of protective coating a workpiece comprising: preparing
the workpiece using the method of claim 1; and nickel coating the
workpiece using electroless nickel coating.
9. The method of claim 8 wherein the nickel coating is performed in
a tank containing a nickel solution, further comprising heating the
nickel solution to about 90.degree. C.
10. The method of claim 9 further comprising: circulating the
nickel solution through an indirect heat exchanger; and circulating
hot water to the indirect heat exchanger for heating the nickel
solution.
11. The method of claim 9 further comprising recirculating the
nickel solution through a filter.
12. The method of claim 8 comprising applying a polymer sealer over
the nickel coating.
13. The method of claim 8 comprising applying a fluoropolymer
sealer over the nickel coating.
14. The method of claim 8 comprising applying a sealer comprising a
dispersion of a PTFE fluoropolymer.
15. The method of claim 9 further comprising: storing the nickel
solution in a carbon steel tank. lining the carbon steel tank with
a plastic liner for storing the nickel solution separated from the
carbon steel tank.
16. The method of claim 15 further comprising: extending the liner
over a top edge of the tank; and arranging one or more bumpers
between the tank and the workpiece for protecting the liner from
damage.
17. The method of claim 16 further comprising: providing a
plurality of the bumpers; and arranging one or more of the
plurality of bumpers between the tank and the workpiece.
18. Apparatus for electroless nickel plating of a workpiece
comprising: a carbon steel tank; and a plastic liner for storing a
nickel solution separated from the carbon steel tank.
19. The apparatus of claim 18 further comprising one or more
bumpers for arrangement between the tank and the workpiece for
protecting the liner from damage.
20. The apparatus of claim 18 further comprising: an indirect heat
exchanger; a hot water heater; a hot water circulation loop between
the hot water heater and the indirect heat exchanger; and a nickel
solution circulation loop between the tank and the indirect heat
exchanger.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefits under 35 U.S.C. 119(e)
of the U.S. Provisional Application Ser. No. 61/771,171, filed on
Mar. 1, 2013, the subject matter of which is incorporated fully
herein by reference.
FIELD
[0002] This subject matter of this disclosure relates generally to
apparatus, process and systems for effectively corrosion-proofing
metal workpieces, more particularly cleaning and plating a steel
workpieces with nickel and protective coatings.
BACKGROUND
[0003] Nickel plating is a process that deposits a thin layer of
nickel onto an underlying metal, often steel. Some of the benefits
of nickel plating include increased resistance to corrosion or
rust, improved resistance to wear, strength and improved ductility.
Workpieces are typically manufactured of vulnerable and inexpensive
materials. Nickel plating is often used in the automotive and oil
and gas industries to protect such materials from corrosion caused
by CO.sub.2 and H.sub.2S.
[0004] Two different methods may be used to add nickel plating to a
workpiece. The first is electrolytic, also called "galvanic". The
second is purely a chemical process known as electroless which
relies upon a chemical reaction to apply the layer of nickel.
[0005] Before performing electroless nickel plating, the material
to be plated is cleaned by a series of chemicals, known as the
pre-treatment process. Chemical cleaning is the standard cleaning
process in the plating industry. Chemical cleaning is only an
effective as the cleaning solution. The success of the cleaning has
a direct impact on the adhesion of the nickel coatings. Workpieces
that are not cleaned properly will have poor adhesion. In
particular, failure to remove unwanted residue or "soils" from the
workpiece's surface result in poor plating. Each pre-treatment
chemical treatment is therefore followed by several water rinses to
remove chemicals that may adhere to the surface. De-greasing
removes oils from surfaces, whereas acid cleaning removes scaling.
The cleaning bath may require frequent replacement at a high cost.
Further, after the cleaning process is complete, the workpiece is
exposed to a Hydrochloric acid (HCl) pre-dip prior to plating.
However HCl pre-dip tends to leave a rust film or "Rose Bloom" on
the surface of the workpiece which also negatively affects the
adhesion of the nickel coating.
[0006] Once the workpiece has been prepared, it is placed in an
alloy tank that is passivated by nitric acid for plating. The tanks
are manufactured of exotic metals resistant to the chemicals and
plating effects. The tanks are typically made of stainless steel or
alloys such as Inconel.RTM. (International Nickel Company, Inc.).
The chemical bath or fluid in the tanks is typically heated by
electric elements or boilers coupled with steam heat exchangers.
Electric elements are expensive, have a limited size of tank they
can heat and may take multiple hours to heat the fluid in the tank.
If an electrical element were to be damaged, it could cause a fire
and pose a safety risk to the workers. Boilers coupled with steam
heat exchangers are far more efficient. However, they have specific
operational and maintenance requirements which are often regulated
and require certified operators with special training. Steam heat
exchangers are not readily serviceable and are typically replaced
when their life cycle ends. Replacing steam heat exchangers can be
expensive and time consuming, with additional revenue lost during a
shut down and servicing.
[0007] The newly plated workpiece is sometimes further coated with
a sealer to enhance the corrosion resistance of the nickel coating.
Unfortunately, most sealers wipe or peel off over time and
effectively offer little to no additional protection.
[0008] There is a need for an improved nickel plating process and
equipment in the coating industry.
SUMMARY
[0009] Generally, a pre-treatment process prepares workpieces, such
as iron-bearing workpieces, for subsequent electroless nickel
coating. The pre-treatment process comprises thermal heat soaking
and garnet grit blasting. Further, the workpiece can be submerged
in hot ammonia, all of the above pre-treatment steps resulting in
minimal residue and actors adverse to subsequent nickel plating
operations.
[0010] Further, use of expensive tank materials for electroless
nickel coating can be avoided through the use of mere carbon steel
tanks protected by replaceable plastic liners. Somewhat fragile
liners can be optionally protected from the subject workpieces
using movable panels suspended strategically about the tank walls.
Further, tank heating is effectively provided using industrial hot
water heaters and an indirect water/nickel solution heat exchanger,
obviating the need for risky and regulated heat sources such as
electrical or steam heating. In a final option, a fluoropolymer
sealer can be provided over the nickel coating.
[0011] In a broad aspect a pre-treatment method for preparing a
workpiece for plating comprises heat-soaking the workpiece for
thermal removal of residue therefrom, optionally at about
400.degree. C. for about 8 hours, and blasting the residue-free
workpiece with garnet grit. Further, the process can include
submerging the workpiece in hot ammonia.
[0012] In another aspect, the aforementioned pre-treatment
methodology is preparatory for a method of coating the workpiece
with a protective coating including using electroless nickel
coating. The nickel coating can be conducted in a tank containing a
nickel solution, whilst heating the nickel solution to about
90.degree. C. The nickel solution can be heated by circulating the
nickel solution through an indirect heat exchanger; and circulating
hot water to the indirect heat exchanger for heating the nickel
solution. Further, the nickel coated workpiece can be further
protected with a polmer sealer, such as a fluoropolymer sealer.
[0013] In another aspect, the electroless nickel coating can be
conducted in apparatus comprising a carbon steel tank; and a
plastic liner for storing a nickel solution separated from the
carbon steel tank. The apparatus can also comprise one or more
bumpers for arrangement between the tank and the workpiece for
protecting the liner from damage. The nickel solution can be heated
using a heating system further comprising: an indirect heat
exchanger; a hot water heater; a hot water circulation loop between
the hot water heater and the indirect heat exchanger; and a nickel
solution circulation loop between the tank and the indirect heat
exchanger.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1A is a flow chart of various embodiments of workpiece
surface preparation including thermal cleaning, grit blasting, and
hot ammonia pre-dip;
[0015] FIG. 1B is a flow chart of various embodiments of workpiece
surface plating and sealing including nickel coating and polymer
sealing;
[0016] FIG. 2 is an end cross-sectional view of an ENC tank having
a liner, a plurality of safety bumpers and a workpiece such as a
valve body being lowered by rack into the tank;
[0017] FIG. 3A is an embodiment of an electroless nickel coating
(ENC) or plating embodiment illustrating hot water heaters, hot
water loops, an indirect heat exchanger and ENC tank;
[0018] FIG. 3B is a schematic overview of the heating system
according to the ENC embodiment of FIG. 3A including an optional
ENC tank filter; and
[0019] FIG. 4 illustrates scanning electron microscope or SEM
images of a first iron workpiece coated with nickel and a second
iron workpiece coated with nickel and then coated with a subsequent
fluoroploymer sealer according to embodiments disclosed herein.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] In accordance with one aspect of the disclosure, there is
provided a cleaning process, a nickel coating and sealing process,
and methods of providing protective coatings upon parts and
components, referred to generically herein as workpieces, for
improving corrosion resistance of said workpieces to toxic
environments that can cause premature wear or failure in industries
including oil and gas and automotive. The coating process includes
preparation of the surface of the workpiece, electroless nickel
coating or plating in a chemical bath, and sealing the plated
workpiece with a sealant.
[0021] Generally, workpieces to be protected are prepared using a
thermal process to remove substantially all residues adverse to
subsequent and relevant coating processes referred to herein.
Further, the workpiece surface is further treated to improve
coatings adhesion, more particularly using a grit blasting.
Iron-bearing workpieces can further be advantageously pre-treated
using a hot ammonia bath. Embodiments of nickel-plating tanks are
provided herein having advantages in ease of construction,
scalability, and heating. Low cost tanks can be employed having
replaceable liners secured thereto. Heating is provided using hot
water heaters, obviating the need for troublesome and expensive
electrical or steam boilers. In a final option, a fluoropolymer
sealer can be applied which is particularly effective in adhering
to the nickel.
[0022] Herein, workpieces to be coated typical include valves and
other workpieces manufactured of base materials vulnerable to
corrosion including steel.
Surface Preparation
[0023] With reference to FIG. 1A, a pre-treatment surface
preparation process is useful prior to plating and maximizes the
effectiveness of nickel coating.
[0024] A first step in an embodiment of the surface preparation
process is to clean a workpiece 10 as shown in Blocks 100, 110 and
120.
Thermal Cleaning
[0025] At Block 100, the workpiece 10 is thermally cleaned in an
oven 20. Applicant has found that, a majority of the time, thermal
cleaning is most effective for removing foreign substances from the
workpiece 10 for ensuring sufficient adhesion of materials during
subsequent plating processes. The oven 20 is heated to about
400.degree. C. and the workpiece 10 is heat-soaked for a duration
of about eight hours. Thermal cleaning leaves no chemical residue
on the surface of the workpiece, maximizing adhesion of subsequent
nickel coating in the plating process.
Grit Blasting
[0026] At Block 110, a next step in preparing the surface of the
workpiece 10 for plating is grit blasting. Most conventional
abrasive grit such as aluminum oxide, steel shot, or silica grits
provide minimal surface roughening and grit residue is damaging to
subsequent nickel coating chemicals and processing. Applicant has
determined that a garnet grit is suitable for pre-nickel plating
preparation without the aforementioned disadvantages. In one
embodiment, garnet abrasive grit is used in the blasting process
for creating a uniform surface profile virtually free of grit
embedment, and providing an excellent roughened surface for coating
adhesion.
[0027] A source 30 of grit 32 is provided for delivery to blasting
apparatus 34 for delivery under pressure to the workpiece 10. An
effective size for the garnet grit or abrasive particles is about
120 mesh (Tyler Equivalent). The pressure ranges of the blasting
apparatus 34 can range from about 60 psi to about 80 psi with a
preferred pressure of about 75 psi. The grit blasting is done to a
National Association of Corrosion Engineers (NACE) specification #1
standard.
Hot Ammonia Bath
[0028] At Block 120, once the grit blasting is complete, the
workpiece 10 is placed into a hot ammonia bath 40 for the final
stage of the surface preparation. The ammonia bath has a
concentration ranging from about 0.06% to about 0.10% and is heated
to a temperature range of about 60.degree. C. to about 75.degree.
C. The workpiece 10 is submerged in the bath 40 for about 0.5 hours
to about 1.5 hours as appropriate depending on the thickness and
volume of the workpiece 10. The hot ammonia bath 40 is used to
lessen or eliminate any potential rust film or "rose bloom" that
could otherwise occur on the workpiece's surface.
[0029] At Block 130, the workpiece 10 is removed from the ammonia
bath 40 and ready for plating.
Plating
[0030] Once the workpiece 10 has been prepared, electroless nickel
plating (ENC) can be effectively implemented. ENC is known in the
art and comprises deposition of a nickel-phosphorous or
nickel-boron alloy onto the workpiece. A known reducing agent
reacts with metal ions in a metal workpiece to deposit the coating.
Herein, the plating process is known however the tank and heating
process are improved over the known apparatus and
methodologies.
[0031] A nickel super alloy coating result that imparts superior
corrosion resistance and added wear resistance to the workpiece.
The coating is a grain-free amorphous structure with excellent
barrier corrosion protection. The morphology of the coating is
similar to that of a metallic glass coating, the absence of a
well-defined crystal structure avoiding intergranular corrosion.
Typically, in a nickel-phosphorous system, the process results in
coating having a nickel metal content (wt %) of about 87.5%-89.5%
and a phosphorus content (wt %) of about 10.5% to 12.0% with traces
of other elements.
[0032] Turning to Block 140, the workpiece 10 is lowered into an
ENC tank. The tank includes a liner 52 and a heated nickel coating
solution 54. The coating solution 54 is heated through an indirect
heat exchanger 56. An industrial hot water heater 58 provides the
heat source for the heat exchanger 56. The workpiece is plated with
nickel forming a nickel plated workpiece 10N.
[0033] At Block 150, the nickel-plated workpiece 10N is introduced
to a sealer tank 60 for submergence of the workpiece 10NS or a
spray booth for larger workpieces 10N. A sealer 62 is applied
forming a sealed, nickel-plated workpiece 10NS.
[0034] In an embodiment, a fluoropolymer sealer 62 is used to
enhance corrosion resistance of the nickel coating. The advantage
of the fluoropolymer sealer is it does not wipe off or peel off as
prior art sealers or dyes do. Applicant believes this is
accomplished by the nature of the chemical bonding between the
sealer and the nickel coating.
[0035] With reference to FIGS. 1A to 3, various arrangements and
configurations of the plating equipment, and operation thereof, are
described in greater detail.
Coating Equipment
[0036] With reference to FIG. 2, upon completion of the surface
preparation, the workpieces 10 are treated in the nickel plating
tank 50. The workpieces can be arranged and supported in a rack or
basket for processing in tank 50. In the present embodiment, ENC
treating tanks 50 can up to 35 feet long for long tubular
workpieces. Custom tanks can be made that can accommodate a larger
workpieces, Applicant regularly provides tanks 50 having dimensions
in the order of 6 feet wide by 10 feet long by 6 feet deep.
[0037] In the prior art, stainless steel tanks are typically
passivated by nitric acid to maximize the natural anti-corrosion
properties of the stainless steel. Continuous operation requires
alternating operation of dual tanks sitting side-by-side for every
operational set up. Typically one tank is in operation and the
other is being passivated with nitric acid. The time required to
passivate one tank is several days.
[0038] Instead, in embodiments disclosed herein, mere carbon steel
tanks can be used, implementing a replaceable plastic liner just
slightly smaller than the tank itself. Accordingly a tank 50 has
walls 70, made from a less expensive material such as carbon steel,
can be used in combination with the inexpensive liner 52.
Accordingly, tanks of virtually any dimensions can be readily
manufactured or modified for various configurations at a fraction
of the cost of tanks manufactured of more expensive, exotic
corrosion resistant materials. Thus, the nickel solution can be
stored in the carbon steel tank, the carbon steel tank 50
incorporating the plastic liner 52 for storing the nickel solution
separated from the carbon steel tank.
[0039] In an embodiment, dual side-by-side tanks can still be
employed for alternating use; one tank being used for plating while
the alternate tank's polypropylene liners are changed out, the time
and cost to replace liners 52 being substantially less than that
for prior stainless steel tanks.
[0040] The carbon steel tank 50 comprises an open top 72 having a
top edge 74 about a perimeter of the enclosing walls 70. The liner
52 is positioned inside the tank 50 for forming a liquid
containment and is stretched out over the top edge 74, protecting
the material of the tank walls 70. The liner can be disposable or
cleaned.
[0041] Workpieces 10 are lowered into the tank 70 in a basket, from
a rack 76 or other apparatus. The liner 52 is at risk of damage
from the suspended workpieces. Accordingly, as shown, one or more
wall panels or safety bumpers 77 formed of sheet materials are
provided, such as those made from a durable material such as
Polytetrafluoroethylene (PTFE) or Teflon.RTM. (registered trademark
of DuPont) are movable and are installed at various points along
the perimeter of the tank 50 to protect the liner 52 from damaging
contact with workpieces. One means for retaining the safety bumpers
77 is to incorporate a "U" shaped hook or holder 78 at an upper end
for engaging the top edge 74 of the tank, a downwardly depending
panel portion 79 sandwiching the liner against the wall 70. The
panel portion 79 of the bumper extends toward the bottom of the
tank adjacent the interior of the perimeter wall 70 for protecting
the liner. A plurality of safety bumpers 77 can be placed and moved
anywhere about the perimeter of the tank as necessary. for
protecting the liner from damage.
[0042] The bumpers 77 can be strategically arranged placed between
the tank and the workpiece dependent upon workpiece ingress and
egress locations or be implemented along substantially the entirety
of the tank walls 70. Overhead fluid lines can strategically access
the tanks fluid contents spaced inwardly from the liner 52 or
aligned with bumpers 77 to minimize risk of liner damage.
[0043] In one embodiment, the liner 52 is a disposable
polypropylene material. When the bath needs to be emptied the
polypropylene liner 52 can be reused or simply discarded. The liner
can be continuous into and out of which fluids are passed from
overhead fluid lines. Alternatively, the liner can be manufactured
with an integrated outlet, and optionally an integrated fluid inlet
for in-tank fluid access.
[0044] In an embodiment, an advantage of using a disposable liner
52 is that only one operational tank could be required as the
change out time is minimal, being four hours or less, minimally
impacting operations. Also, capital costs for using a carbon steel
material for the tank 50 with a liner 52 are typically less than
one third the cost of using a stainless steel tank. The
polypropylene liners 52 can be custom made to fit any size tank 50.
Typically, one polypropylene liner 52 can be used for multiple
cycles, typically two bath cycles.
Heating the Coating Tanks
[0045] With reference to FIGS. 1B, 3A and 3B, a heating system for
the nickel plating process is provided. A nickel coating solution
used in plating processes is maintained, within the ENC tank, at a
temperature of about 90.degree. C. Industrial hot water heaters 58
with large capacity heat exchangers 56 are utilized for providing
the heat source required for the nickel plating process. Such hot
water heaters are easy to operate and maintain and do not require
specially certified workers to operate as do steam heat
sources.
[0046] The industrial hot water heaters indirectly heat the
solution. Large capacity plate-type heat exchanges 56 are
serviceable and easy to maintain compared to electric elements and
boilers. The cost for heating the system is less than that
associated with electric elements and steam boilers commonly used
in the industry.
[0047] The hot water heater, such as a boiler, heats water and
circulates the hot water through a main loop using a main lop pump.
When heat is required for electroless nickel coating tank, a
primary pump pulls water from the main loop and circulates the hot
water to a plate heat exchanger. Similarly, a recirculation pump
circulates nickel solution through the same heat exchanger for
heating the solution. The heat demand by one or more heat
exchangers and the resulting heat loss from the main loop is
reheated by the hot water heater.
[0048] In more detail, and having reference to FIGS. 3A and 3B, a
main heated water loop 80 acts as an intermediary stage between the
hot water heater 58 and heat exchanger 56. The heat exchanger 56
has a heat-providing side and a heat-receiving side, for heating
and maintaining the nickel coating solution bath at a temperature
of about 90.degree. C. Thus, the heating system comprises the
indirect heat exchanger 56, the hot water heater 58; hot water
circulation loop 80 between the hot water heater and the indirect
heat exchanger; and a nickel solution circulation loop 91 between
the tank 50 and the indirect heat exchanger 56.
[0049] Hot water is provided to the main loop 80 by a hot water
boiler pump 82. A main hot water loop pump 84 circulates the hot
water through the main loop 80. The main loop can provide heat for
one or more of the process needs such as a heat exchanger serving
the hot ammonia bath.
[0050] A temperature sensing device, such as a thermocouple 86,
monitors the temperature of the nickel coating solution bath in
tank 50. When the bath temperature falls below a predetermined
threshold temperature, the main heated water is routed through the
heat exchanger 56 by a primary pump 88.
[0051] With regards to the heat receiving side, a recirculation
pump 90 is provided for circulating the nickel coating solution
along the nickel solution circulation loop 91 to and from the
treating tank 50. The solution receives heat from the heated water
at the heat exchanger 56 and is circulated back into the treating
tank 50. The solution is circulated through a filter 92 with a
filter pump 94 for maintaining a desired quality of the nickel
coating solution for coating the workpiece, and maximizing the
solution life.
[0052] Upon completion of the nickel coating process the workpiece
10 is inspected for quality assurance purposes and then sent to the
sealer tank.
Sealer
[0053] Returning to FIG. 1B, a fluoropolymer sealer is used to
enhance corrosion resistance of the nickel coating, the
effectiveness of which is believed effective due to a chemical
bonding between the PTFE and the nickel. A particularly effective
fluoropolymer sealer for application over nickel coatings, such as
for excellent chemical corrosion resistance for CO.sub.2, H.sub.2S,
brine and chlorides, is a polytetrafluoroethylene (PTFE). A
suitable PTFE is Teflon.RTM. (a registered trademark of DuPont)
such as an acqueous dispersion of PTFE TE-3893 fluoropolymer resin
made by DuPont.TM.. As set forth in DuPont's product information
for PTFE TE-3893 fluoropolymer resin, the product is a milky white
liquid containing typically 60% (total wt %) of 0.05 to 0.5 um of
PTFE particles suspended in water and may contain 6% (wt % of PTFE)
of a non-ionic wetting agent and stabilizer. The sealer is suitable
for conventional dip or flow techniques.
[0054] The sealer tank 60, which is typically about 6 feet long by
35 inches wide by 4 feet deep is used to submerse the nickel-plated
workpiece 10N in the PTFE resin for about 5 minutes at room
temperature (approximately 20.degree. C. to about 25.degree. C.).
If the workpiece 10N is too large to be submerged in the sealer,
the sealer 62 can also be applied by spraying the nickel surface.
After spraying, excess sealer 26 can be rinsed off of the workpiece
10NP. For fluoropolymer resins, excess sealer 62 can be rinsed off
after about 5 minutes.
[0055] The sealer can be applied in a single coat application or
multiple coats if required and is self-lubricating and non-stick.
The sealer coating results in a low coefficient of friction,
providing a high level of release and non-stick properties.
[0056] The advantage of the fluoropolymer sealer is it does not
wipe off or peel off as prior art sealers or dyes do. Applicant
believes this is accomplished by the nature of the chemical bonding
between the sealer and the nickel coating.
[0057] As shown in FIG. 4, a scanning electron microscope or SEM of
a cross-section of two iron (Fe) workpiece surfaces are
illustrated, both having nickel (Ni) coating, and one workpiece
10NS having a PTFE sealer and the other workpiece 10N without.
* * * * *