U.S. patent number RE35,860 [Application Number 08/722,752] was granted by the patent office on 1998-07-28 for corrosion-resistant zinc-nickel plated bearing races.
This patent grant is currently assigned to MPB Corporation. Invention is credited to Peter C. Ward.
United States Patent |
RE35,860 |
Ward |
July 28, 1998 |
Corrosion-resistant zinc-nickel plated bearing races
Abstract
A rolling element bearing includes a first ring having a first
raceway; a second ring having a second raceway, and rolling
elements between the two raceways. The first and second rings are
positioned and configured so that the first and second raceways
form a channel which retains the rolling elements. A first zinc
alloy plated layer is on the first ring including at the first
raceway, and a second zinc alloy plated layer is on the second ring
including at the second raceway. The rolling elements may also be
plated with a zinc alloy layer. The layers are porous and thus
permit hydrogen to escape from the rings and rolling elements when
baked, so that the rings and rolling elements possess low hydrogen
embrittlement. The layers provide physical and galvanic protection
to the underlying substrates for the rings.
Inventors: |
Ward; Peter C. (Peterborough,
NH) |
Assignee: |
MPB Corporation (Keene,
NH)
|
Family
ID: |
27108494 |
Appl.
No.: |
08/722,752 |
Filed: |
October 1, 1996 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
710656 |
Jun 5, 1991 |
|
|
|
Reissue of: |
923371 |
Jul 31, 1992 |
05352046 |
Oct 4, 1994 |
|
|
Current U.S.
Class: |
384/492; 384/913;
384/625 |
Current CPC
Class: |
F16C
33/62 (20130101); F16C 33/32 (20130101); F16C
19/06 (20130101); F16C 2204/50 (20130101); F16C
19/52 (20130101) |
Current International
Class: |
F16C
33/62 (20060101); F16C 33/62 (20060101); F16C
33/32 (20060101); F16C 33/32 (20060101); F16C
33/30 (20060101); F16C 33/30 (20060101); F16C
033/62 () |
Field of
Search: |
;384/492,625,913,491,276,912 ;204/44.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0288677 |
|
Feb 1988 |
|
EP |
|
247049 |
|
Jun 1987 |
|
DD |
|
1907897 |
|
Oct 1969 |
|
DE |
|
7918966 |
|
Oct 1980 |
|
DE |
|
3316678 |
|
Nov 1983 |
|
DE |
|
3414048 |
|
Oct 1985 |
|
DE |
|
3933896 |
|
Oct 1990 |
|
DE |
|
137621 |
|
Aug 1983 |
|
JP |
|
60-241516 |
|
Nov 1985 |
|
JP |
|
732268 |
|
Jun 1955 |
|
GB |
|
2119814 |
|
Nov 1983 |
|
GB |
|
2121120 |
|
Dec 1983 |
|
GB |
|
Other References
Investigation of Nickel-Cadmium-Diffused and Cadmium Plating
Replacement Coatings, C. Smith, 92APF-12, Allied-Signal Aerospace
Company. .
SAE Paper 920943, C. Smith, Apr. 20, 1992. .
SAE Paper 830686, A New Zinc-Nickel Electroplating Process:
Alternative to Cadmium Plating, G Hsu, 1983. .
Plating and Surface Finishing Zinc-Nickel Alloy Plating: An
Alternative to Cadmium, G. Hsu, Apr. 1984. .
SAE Paper 840815, Low Hydrogen Embrittlement Zinc-Nickel
Electroplating: An Alternative to Cadmium-Update, G.Hsu 1985. .
Oberflache+JOT, Helmut Enger, Zinc-Nicle, Alternative zur inormalen
Verzinkung, 1989, publication 7, pp. 26 and 27. .
SAE Technical Paper Series (841124), Extending Bearing Life in
Off-Highway Equipment, International Off-Highway & Powerplant,
Congress & Exposition, W. Waskiewicz, Sep. 1984. .
SKF Umwertungstabells fur Vickersharte 1976. .
SKF catalog 4000T, 1984, pp. 126,127. .
Metal Finishing, Electrodeposition of Tungsten Alloys, M.
Sarojamma, 1971. .
Thyssen Edelstahl, Tec. Ber., vol. 11, Pamphktz, Sep. 1985. .
ATC Metalltechnologie, Amoloy Technology Coating, Sep. 1987. .
Deutsche Norm, DIN 69051, Apr. 1989. .
Deutsche Star, Das Linear-Programming, Jun. 1989. .
Thomson Industries, Linear Motion Designer's Guide, Feb. 1984.
.
Technische Oberlfachen, Beuth Kommentare, 1981, pp. 32-35. .
Metallwissenschaft+Technik, Electrodeposition Behavior of Ternary
Zinc-Iron-Nickel Alloys, T, Akiyama, 1989. .
Walzlager, Theorie and Praxis, M. Albert, 1987, p. 368. .
Deutsche Star, Star Kugelrollen, 1987. .
Das Techniker Handbuch, A. Boge, 1985, pp. 670,671. .
Walzlager, Theorie and Praxis, M. Albert, 1987, pp. VII-XVII,
19-22. .
Smith, pp. 11 and 12 date & title unknown..
|
Primary Examiner: Hannon; Thomas R.
Attorney, Agent or Firm: Polster, Lieder, Woodruff &
Lucchesi, L.C.
Parent Case Text
RELATED APPLICATION
This application is a continuation-in-part of application Ser. No.
07/710,656 filed Jun. 5, 1991.
Claims
What is claimed is:
1. A rolling element bearing comprising:
a first race having a first raceway;
a second race having a second raceway, said first and second races
being positioned so that said first and second raceways form a
channel;
a first zinc alloy plated layer on said first race along the first
raceway thereof;
a second zinc alloy plated layer on said second race along the
second raceway thereof; and
a plurality of rolling elements disposed within said channel formed
by said first and second raceways.
2. The rolling element bearing of claim 1 further comprising a
lubricant within said channel.
3. The rolling element bearing of claim 2 wherein said lubricant is
a grease.
4. The rolling element bearing of claim 2 wherein said first race
is an inner bearing ring and said second element is an outer
bearing ring.
5. The rolling element bearing of claim 4 wherein each of said
rolling elements is spherical.
6. The rolling element bearing of claim 1 wherein zinc alloy of the
plated layers is porous and the first and second races have low
hydrogen embrittlement by reason of hydrogen formerly contained
within the races having escaped through the pores in the layers of
those races.
7. The rolling element bearing of claim 1 wherein said first and
second zinc alloys are zinc-nickel alloys.
8. The rolling element bearing of claim 1 wherein the thickness of
each of the first and second zinc alloy layers is less than about
0.0010 inch.
9. The rolling element bearing of claim 8 wherein the thickness of
each of the first and second zinc alloy layers is between about
0.0003 and 0.0005 inches remote from the raceways.
10. The rolling element bearing of claim 1 wherein each of said
plurality of rolling elements includes a zinc alloy plated layer on
its surface.
11. The rolling element bearing of claim 10 wherein the zinc alloy
plated layer on each of said plurality of rolling elements is less
than about 0.0001 inch.
12. An antifriction bearing comprising:
a first race having a raceway;
a second race having a raceway that is presented toward the raceway
of the first race;
at least one of the races including a substrate and zinc alloy over
the substrate in the form of a plating, the zinc alloy plating
being at the raceway of the first race and elsewhere on the first
race as well, the zinc alloy plating having microscopic pores which
extend through it from the substrate to its exposed surface;
and rolling elements located between the races at the raceways
thereof.
13. A bearing according to claim 12 wherein substrate of said one
race is steel having low hydrogen embrittlement by reason of having
been heated to the extent that hydrogen formerly contained within
it has been driven off through the pores in the zinc alloy
layer.
14. A bearing according to claim 12 wherein each race has a
substrate of steel and a zinc alloy plating over the substrate, and
the steel substrate has low hydrogen embrittlement.
15. A bearing according to claim 14 wherein the zinc alloy plating
on each of the races is applied electrically and also includes
nickel.
16. A bearing according to claim 15 wherein the zinc alloy plating
on each of the races covers substantially the entire race.
17. A bearing according to claim 14 wherein each rolling element
includes a steel substrate and a zinc alloy plating over the
substrate.
18. A bearing according to claim 17 wherein the zinc alloy plating
on the rolling elements includes nickel.
19. A bearing according to claim 12 wherein the zinc alloy plating
of said one race covers substantially the entire race.
20. A bearing according to claim 12 wherein the zinc alloy layer
also contains nickel. .Iadd.
21. An antifriction bearing comprising:
a first race having a raceway;
a second race having a raceway that is presented toward the raceway
of the first race;
at least one of the races including a substrate and zinc alloy over
the substrate in the form of a plating, the zinc alloy plating
being at least along the raceway of said one race; and
rolling elements located between the races at the raceways thereof.
.Iaddend..Iadd.22. A bearing according to claim 21 wherein the zinc
alloy plating of said one race covers substantially the entire
race. .Iaddend..Iadd.23. A bearing according to claim 21 wherein
the zinc alloy plating also contains nickel. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The invention relates to corrosion resistant rolling element
bearings and a process for producing races for such bearings.
Some bearing applications require bearings which are capable of
both enduring high loads and surviving in very corrosive
environments. For example, so-called airframe bearings, such as,
the bearings on which the control surfaces and flaps of aircraft
oscillate, must survive exposure to moisture and deicing fluids,
not to speak of salt spray on occasions. Moreover, these bearings
experience wide variations in pressure which cause them to ingest
fluids, bringing those fluids into contact with the raceways which
deteriorates the raceways. Bearings for machinery used in the food
processing industry likewise operate in hostile environments
characterized by aqueous corrosion. The high strength material from
which high load bearings are typically made (e.g., 52100 bearing
steel) does not provide the required level of corrosion resistance
for such environments.
In an effort to improve the corrosion resistance of such bearings,
other base materials, such as 316 stainless steel, have been
utilized. A problem with many such alternative base materials,
however, is that they are not hardenable and thus are not capable
of providing the required load handling capabilities of the high
strength steels. Other stainless steels, such as 440C stainless,
are hardenable, but do not have sufficient resistance to corrosion.
Thus, insofar as the stainless steels are concerned, they are
either corrosion resistant and incapable of acquiring suitable
hardness or else capable of being hardened and incapable of
resisting corrosion.
Another approach has been to deposit Thin Dense Chrome (TDC), that
is, a very hard plating of chromium onto, the exposed areas
including the wear or functional surfaces, such as the raceways
along which the rolling elements roll. With TDC, however, it is
very difficult to obtain sufficiently thick layers while still
achieving the required level of consistency, that is, an absence of
holes and surface flaws which provide focal points at which
corrosive activity tends to occur. In this regard, chromium is
noble to steel in most corrosive environments, and thus any break
in the chromium coating will cause the steel to corrode at that
break. Hence, the chromium must form a perfect physical
barrier.
Yet another approach has been to deposit cadmium protective layers,
which are soft in comparison to the hardened, high strength steel
from which the bearing is constructed. Due to its softness and
other characteristics, cadmium is not well suited for use on the
functional surfaces. Under load conditions, the cadmium may
separate from the steel base material and interfere with the
operation of the bearing or otherwise is quickly worn off, thereby
eliminating the physical and galvanic protection which it
originally provided. As a consequence, in cadmium plated bearings,
the cadmium does not exist along the functional surfaces, but
instead the steel is exposed at these surfaces. Apart from that,
the plating solution from which cadmium is derived also contains
cyanide which is extremely toxic. Environmental regulations do not
favor cadmium plating by reason of the toxicity of the plating
solution.
Most processes for plating steel rely on electrochemical reactions
within plating solutions that contain and indeed often liberate
hydrogen. During the process the steel absorbs hydrogen, and the
hydrogen embrittles the steel. But a measure of ductility, not
brittleness, is desired in bearing races and the rolling elements
which move along them. Cadmium deposits on steel in a somewhat
porous condition, and one can relieve hydrogen embrittlement simply
by baking the steel part after it is plated. During baking the
hydrogen escapes through the pores in the coating. Some other
metals deposit on steel in a generally impervious condition and in
effect trap hydrogen in the steel so that it cannot be easily
driven off by baking. Zinc and traditional zinc alloys have
exhibited this characteristic when deposited by conventional
electroplating processes.
SUMMARY OF THE INVENTION
In general, in one aspect, the invention features a rolling element
bearing including a first race having a first raceway and a second
race having a second raceway. The first and second races are
positioned relative to each other so that the first and second
raceways form a channel. The rolling element bearing also includes
a first zinc alloy plated layer on the first raceway, a second zinc
alloy plated layer on the second raceway, and a plurality of
rolling elements disposed within the channel formed by the first
and second raceways.
Preferred embodiments include the following features. The rolling
element bearing also includes a lubricant (e.g. a grease) within
the channel. The first and second zinc alloys are zinc-nickel
alloys. The first race is an inner bearing ring and the second race
is an outer bearing ring. Each of the rolling elements is a
spherical bearing ball. The thickness of each of the first and
second zinc alloy layers is between about 0.000050 and 0.000150
inch at the raceways and elsewhere is less than about 0.0010 inch,
and preferably between about 0.0003 and 0.0005 inch. Each of the
rolling elements may include a zinc alloy plated layer on its
surface, with the thickness of the zinc alloy layer being between
about 0.000025 and 0.0001 inch.
In general, in another aspect, the invention features a rolling
element bearing including an inner ring having an outer raceway; an
outer ring having an inner raceway, and the inner and outer rings
being positioned so that the inner and outer raceways form a
channel; a first zinc alloy plated layer on the inner raceway; a
second zinc alloy plated layer on the outer raceway; a plurality of
bearing balls disposed within the channel formed by the inner and
outer races; and a lubricant within the channel.
Still another aspect includes the process of providing a substrate,
applying a zinc alloy layer to the substrate by an electroplating
process which leaves the layer with microscopic channels, and
heating the substrate and layer to drive hydrogen from the
substrate out through the pores in the zinc alloy layer.
One advantage of the invention is that it exhibits excellent
galvanic corrosion protection on the high load, plated functional
surfaces of rolling element bearings. Experiments have shown that
even after 100 hours of exposure to salt spray in accordance with
ASTM B117, the functional surfaces or the bearing rings which have
been plated with zinc-nickel showed an absence of corrosion.
In addition, the zinc-nickel plating is somewhat porous in the
sense that it contains microscopic fissures or channels which are
interconnected between the steel-plating interface and the exposed
face of the plating and allow hydrogen to escape from the steel
when the plated steel is baked.
Moreover, even though the zinc-nickel plating is softer than the
underlying high strength steel from which the bearing is made, it
withstands the rolling contact under high load conditions (e.g. in
excess of 150,000 p.s.i.). In addition, it does not degrade the
underlying base material and thereby limit the load carrying
capabilities of the bearing.
Other advantages and features will become apparent from the
following description of the preferred embodiment and from the
claims.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a cross-sectional view of a portion of a bearing assembly
having inner and outer rings and balls between them, all made in
accordance with and embodying the present invention;
FIG. 2 is a cross-sectional view of a portion of the outer
ring;
FIG. 2A is a fragmentary expanded view, in section, of the outer
ring illustrated in FIG. 2 and showing the zinc-nickel plated
layer;
FIG. 3 is a cross-sectional view of a portion of the inner ring;
and
FIG. 3A is a fragmentary expanded view, in section, of the inner
ring illustrated in FIG. 3 and showing the zinc-nickel plated
layer.
STRUCTURE AND OPERATION
FIG. 1 shows a bearing assembly 10 which will be used to illustrate
the invention. Bearing assembly 10 includes an outer race or ring
12, an inner race or ring 14 and a set of rolling elements or
bearing balls 16 (only one of which is shown) arranged in a single
row between the two rings 12 and 14. An outer raceway 20 is formed
around the inside circumference of outer ring 12 and an inner
raceway 18 is formed around the outside circumference of inner ring
14. When inner ring 14 is assembled into outer ring 12, the outer
and inner raceways 20 and 18 are aligned with respect to each other
so as to form a channel which holds the set of bearing balls 16.
Thus, inner ring 14 is free to rotate with respect to the outer
ring 12 or vice versa about a common axis which is perpendicular to
the planes of both rings 12 and 14. The channel also contains a
lubricant 21. That lubricant may be a grease, such as Mobil 28
grease sold by Mobil Oil Corporation, or a liquid lubricant, such
as oil, or even a solid lubricant, such as graphite.
As shown in greater detail in the exploded views in FIGS. 2A and
2B, a zinc-nickel plated layer 22 covers outer raceway 20 and a
zinc-nickel plated layer 24 covers inner raceway 18. In the
described embodiment, the thickness of the plated layers 22 and 24
within the raceways is between approximately 0.000050 and 0.000150
inch. Zinc-nickel plated layers 22 and 24 provide protection
against corrosion which might tend to be caused by environmental
conditions, e.g. the presence of salt water.
Zinc-nickel layers 22 and 24 are applied by an electrical plating
process as described in U.S. Pat. No. 4,765,871 issued to G. Hsu et
al. on Aug. 23, 1988, and U.S. Pat. No. 4,818,632 issued to G. Hsu
et al on Apr. 4, 1989, both of which are incorporated herein by
reference. Further information concerning the plating process and
the zinc-nickel plating derived from it appears in SAE Paper 830686
entitled "A New Zinc-Nickel Electroplating Process Alternative to
Cadmium Plating", Grace F. Hsu, reprinted from Proceedings of the
19th Annual Airline Plating & Metal Finishing Forum, page 127,
which paper is also incorporated herein by reference. In the
described embodiment, zinc-nickel is electroplated onto the entire
outer ring 12 and the entire inner ring 14, including the raceways
20 and 18 of those rings. During the plating process, however,
inner ring 14 is oriented within the electroplating bath relative
to the zinc and nickel anodes so as to control the thickness of the
plating which is formed on the outboard faces 28 of inner ring 14
to be within the range of 0.0003 to 0.0005 inch. The thickness of
the plating on the raceway 18 of inner ring 14 is typically less
than the controlled thickness, it being within the range of
0.000050 to 0.000150 inch in this region. Similarly with outer ring
12, during the plating process, it is oriented within the
electroplating bath relative to the zinc and nickel anodes so as to
control the thickness of the plating which is formed on the outside
surface 30 and outboard faces 33 of outer ring 12 to also be within
the range of 0.0003 to 0.0005 inch. As with inner ring 14 the
thickness of the plating on the raceway 20 of the outer ring 12 is
also typically less than this controlled thickness, it likewise
being between about 0.000050 and 0.000150 inch.
The plating process yields zinc-nickel layers 22 and 24 which are
porous in the sense that they contain microscopic escape channels.
These channels extend completely through the layers 22 and 24 from
their interfaces with the steel to the exposed exterior surfaces.
The channels, which are described more fully in U.S. Pat. No.
4,818,632 and SAE Paper 830686, impart a porosity to the layers 22
and 24, and this porosity enables hydrogen, which is absorbed by
the steel during the plating process, to escape when the rings 12
and 14 are heated to about 350.degree. F. and held at that
temperature for about 3.5 hours. Yet the escape channels in the
layers 22 and 24 are small enough to prevent significant amounts of
hydrogen from reaching the steel substrate of the rings 12 and 14
and reembrittling the steel when the bearing assembly 10 containing
the rings 12 and 14 is placed in operation.
The zinc-nickel plated layers 22 and 24 exhibit a hardness that is
in the range of about Rockwell C30 to C45, based on a conversion
from a microhardness technique of testing, which is significantly
softer than the underlying hardened, high strength steel and
significantly softer than the thin dense chrome layers which have
been used to achieve corrosion resistance on the functional
surfaces of high load bearings.
Experiments have indicated that the zinc-nickel plating on raceways
18 and 20 survive 120,000 cycles of 90.degree. rotation under 400
lbs radial load, which is 20% of the maximum rated load. This is
about 2.5 times the normal design life.
Both outer ring 12 and inner ring 14 may be made of metal capable
of withstanding stress levels of greater than 150,000 p.s.i.,
including for example, thru-hardened, high strength steel (e.g.,
52100 bearing steel heat treated to Rockwell C60 or higher) or
case-hardened steel with its hardened region being no less than
0.025 inches thick. In the described embodiment, rings 12 and 14
are fabricated from annealed steel in a conventional manner. The
rough stock is heat treated, tempered one or more times to improve
the toughness of the steel, and then precision ground on surfaces.
As an optional step, the precision ground rings may be baked for
3.5 hours at a temperature of 350.degree. F. prior to the plating
process. After the optional pre-plating bake, a zinc-nickel layer
is electroplated onto rings 12 and 14, including the functional
surfaces, that is, the raceways 18 and 20. To perform the plating,
rings 12 and 14 are rack mounted in the plating bath. They are
suspended on the racks in such a way as to not obstruct plating
onto the functional surfaces.
After the plating process is complete, the rings are again baked
for 3.5 hours at 350.degree. F. to avoid hydrogen embrittlement of
the base metal or substrate. In effect, the baking drives from the
steel rings 12 and 14 hydrogen which they acquired during the
electrochemical plating. The hydrogen passes through the escape
channels in the plated layers 22 and 24 and thus is not trapped in
the rings 12 and 14 by the layers 22 and 24. This post-plating bake
should be done within four hours of when the plating process is
completed.
To extend the life of the bearings, it may also be desirable to
administer a chromate treatment to the surface of the zinc-nickel
layers followed by another bake out. The chromate treatment
prevents "white rust" from forming on the zinc-nickel surface and
postpones degradation of the zinc-nickel layers.
Other embodiments are within the following claims. For example, the
invention has applicability to the general category of rolling
element bearings, which includes among others, bearings which use
tapered rollers and those which use cylindrical rollers. In
addition, any one of a broad range of zinc alloy plated deposits
may be used to provide similar corrosion resistance on the
functional surfaces. Other appropriate zinc alloys include
zinc-tin, zinc-cobalt and zinc-iron, to name a few.
Also, it may be desirable to plate the rolling elements or balls 16
as well as the races or rings 12 and 14. The plating process is
essentially the same, but may utilize a conventional barrel plating
arrangement rather than the rack mount arrangement used for plating
the rings 12 and 14. Due to the micro sliding which the balls 16
experience, it may be desirable to keep the thickness of the plated
layer on each ball 16 to within the range of 0.000025 to 0.0001
inch.
In the operation of the bearing assembly 10, the outer ring 12 will
rotate around the inner ring 14 or the inner ring 14 will rotate
within the outer ring 12. In either event, the balls 16 roll within
the channel formed by the raceways 18 and 20 on the inner, ring 14
and outer ring 12, respectively. In other words, the balls 16 roll
along the raceways 18 and 20, that is to say along the layers 22
and 24 of alloy plating that exist along the raceways 20 and 18.
While the layers 24 and 22 in the regions of the raceways 18 and 20
possess the microscopic channels before the bearing assembly 10 is
placed in service, thus permitting removal of hydrogen from the
underlying steel of the rings 12 and 14, the balls 10 tend to
obliterate the channels during operation. In the presence of the
balls 16, the plated layers 22 and 24 undergo plastic deformation
which tends to close the microscopic channels. But this does not
matter, since the channels have already served their purpose.
Indeed, the obliteration may even be desirable for it provides
smoother surfaces along the raceways 18 and 20 and produces a
further impediment to hydrogen embrittlement from the atmosphere
and to fluids encountered in operation. Actually the layers 22 and
24 under a microscope appear somewhat nodular everywhere, except at
the raceways 20 and 18 where they appear somewhat scuffed or
smeared.
The layers 22 and 24 do not separate easily from the steel of the
rings 12 and 14, and if they do experience any disintegration, it
is usually in the form of small particles. Being primarily zinc,
the particles are quite malleable and hence will not damage the
rings 12 and 14 or the balls 16.
To be sure, the bearing assembly 10 includes seals which close the
annular spaces between the outer and inner rings 12 and 14 at the
ends of the assembly 10. The seals may be fitted to the inner ring
14 and have elastomeric lips which bear against the outer ring 12,
thereby establishing dynamic fluid barriers along the outer ring
12. But the seals may leak, particularly if the bearing assembly 10
is subjected to wide variances in atmospheric pressure, as are
airframe bearings. A drop in pressure will draw contaminants into
the channel formed by the raceways 18 and 20, whereas a rise in
pressure will purge grease from the channel. The layers 22 and 24,
being over the steel at the raceways 20 and 18, prevent the
contaminants from actually contacting the steel and thus
establishes a physical barrier along the raceways 20 and 22. Zinc,
being higher than iron in the electromotive-force series for
practically all corrosive environments further enables the plated
layers 22 and 24 to provide galvanic protection for the steel of
the rings 12 and 14.
Beyond the region enclosed by the seals, the surfaces 30 and 33 of
the outer ring 12 and the faces 28 of the inner ring 14 are
exposed, and the rings 12 and 14 would quickly corrode in these
areas were it not for the plated layers 22 and 24 which exist along
them. The layers 22 and 24 in these regions prevent the steel of
the rings 12 and 14 from coming into contact with the atmosphere
and any fluids to which the bearing assembly 10 may be subjected,
such as deicing solution, salt spray, or simply water. Even if the
physical barrier formed by the layers 22 and 24 is disrupted by
reason of being damaged, the underlying steel of the rings 12 and
14 will not corrode owing to the galvanic protection provided by
the zinc of the layers. Likewise, the presence of the fissures or
microscopic channels in the layers 22 and 24 does not result in any
corrosion of the underlying steel in the rings 12 and 14. Thus, the
layers 22 and 24 provide a high level of physical and galvanic
protection for the steel substrates of the rings 12 and 14.
* * * * *