Note: Descriptions are shown in the official language in which they were submitted.
2193~~9
SUBSTRATE WITH PROTECTIVE
COATING THEREON
Field of the Invention
The instant invention relates to metallic substrates such as
brass coated with a protective multilayer metallic coating.
Background of the Invention
It is currently the practice with various brass articles such
as lamps, trivets, candlesticks, door knobs and handles and the
like to first buff and polish the surface of the article to a high
gloss and to then apply a protective organic coating, such as one
comprised of acrylics, urethanes, epoxies, and the like, onto this
polished surface. While this system is generally quite
satisfactory it has the drawback that the buffing and polishing
operation, particularly if the article is of a complex shape, is
labor intensive. Also, the known organic coatings are not always
as durable as desired, particularly in outdoor applications where
the articles they are exposed to the elements and ultraviolet
radiation. It would, therefore, be quite advantageous if brass
articles, or indeed other metallic articles, could be provided with
a coating which gave the article the appearance of highly polished
brass and also provided wear resistance and corrosion protection.
The present invention provides such a coating.
Summary of the Invention
The present invention is directed to a metallic substrate
having a multi-layer coating disposed or deposited on its surface.
More particularly, it is directed to a metallic substrate,
particularly brass, having deposited on its surface multiple
2193J~9
68432-291
superposed metallic layers of certain specific types of metals or
metal compounds. The coating is decorative and also provides
corrosion and wear resistance. The coating simulates the
appearance of highly polished brass, i.e. has a brass color tone.
Thus, an article surface having the coating thereon simulates a
highly polished brass surface.
This invention relates to an article comprising a
metallic substrate having disposed on at least a portion of its
surface a multi-layer coating simulating brass comprising: at
least one layer comprised of nickel over at least a portion of said
surface of said substrate; a layer comprised of palladium over at
least a portion of said layer comprised of nickel; a layer
comprised of ruthenium over at least a portion of said layer
comprised of palladium; a layer comprised of zirconium or titanium
over at least a portion of said layer comprised of ruthenium; and a
layer comprised of zirconium compound or titanium compound over at
least a portion of said layer comprised of zirconium or titanium.
This invention also relates to an article comprising a
subst rate having on at least a port ion of its surface a coat ing
simulating brass which comprises a first layer comprised of nickel;
a second layer on at least a portion of said second layer comprised
of palladium; a third layer on at least a portion of said second
layer comprised of ruthenium; a fourth layer on at least a portion
of said third layer comprised of zirconium or titanium; and a fifth
layer on at least a portion of said fourth layer comprised of a
2
219~J~~9
68432-291
zirconium compound or titanium compound.
A first layer deposited directly on the surface of the
substrate is comprised of nickel. Disposed over the nickel layer
is a layer comprised of palladium. This palladium layer is thinner
than the nickel layer. Over the palladium layer is a layer
comprised of ruthenium. Over the ruthenium layer is a layer
comprised of a non-precious refractory metal such as zirconium,
t itanium, hafnium or tantalum, preferably zirconium or t itanium. A
top layer comprised of a zirconium compound, titanium compound,
hafnium compound or tantalum compound, preferably a titanium
compound or a zirconium compound such as zirconium nitride or
titanium nitride, is disposed over the refractory metal layer,
preferably zirconium layer.
The nickel, palladium and ruthenium layers are applied by
electroplating. The refractory metal layer such as zirconium layer
and refractory metal compound layer such as zirconium compound
layer are applied by vapor deposition such as sputter ion
deposition.
Brief Description of the Drawings
FIG. 1 is a cross-sectional view of a portion of the
substrate having the multi-layer coating deposited on its surface.
2a
Description of the Preferred Embodiment
The substrate 12 can be any metal or metallic alloy substrate
such as copper, steel, brass, tungsten, nickel alloys, and the
like. In a preferred embodiment the substrate is brass.
The nickel layer 13 is deposited on the surface of the
substrate 12 by conventional and well known plating processes.
These processes include electroplating processes using
conventional and well known electroplating baths such as, for
example, a Watts bath as the plating solution. Typically such
baths contain nickel sulfate, nickel chloride, and boric acid
dissolved in water. All chloride, sulfamate and fluoroborate
plating solutions can also be used. These baths can optionally
include a number of well known and conventionally used compounds
such as leveling agents, brighteners, and the like. To produce
specularly bright nickel layer at least one brightener from class
I and at least one brightener from class II is added to the plating
solution. Class I brighteners are organic compounds which contain
sulfur. Class II brighteners are organic compounds which do not
contain sulfur. Class II brighteners can also cause leveling and,
when added to the plating bath without the sulfur-containing class
I brighteners, result in semi-bright nickel deposits. These class
I brighteners include alkyl naphthalene and benzene sulfonic acids,
the benzene and naphthalene di- and trisulfonic acids, benzene and
naphthalene sulfonamides, and sulfonamides such as saccharin, vinyl
and allyl sulfonamides and sulfonic acids. The class II
brighteners generally are unsaturated organic materials such as,
3
CA 02193559 1999-11-23
for example, acetylenic or ethylenic alcohols, ethoxylated and
propoxylated acetylenic alcohols, coumarins, and aldehydes. These
Class I and Class II brighteners are well known to those skilled in
the art and are readily commercially available. They are
described, inter alia, in U.S. Patent No. 4,421,611.
The nickel layer is preferably comprised of semi-bright nickel
or bright nickel, more preferably bright nickel. The thickness~of
the nickel layer is a thickness which is effective to provide
improved corrosion protection to the underlying substrate.
Generally this average thickness is from at least about 100
millionths (0.0001) of an inch, preferably at least about 150
millionths (0.00015) of an inch, and more preferably at least about
200 millionths (0.0002) of an inch. The upper thickness limit is
generally not critical and is governed by secondary considerations
such as cost, appearance, and the like. Generally, however, an
average thickness of about 3,500 millionths (0.0035), preferably
about 3,000 millionths of an inch, and more preferably about 2,500
millionths (0.0025) of an inch should not be exceeded.
As is well known in the art before the nickel layer is
deposited on the substrate the substrate is subjected to said
activation by being placed in a conventional and well known acid
bath.
In a more preferred embodiment the nickel layer 13 is
comprised of~two different nickel layers 14 and 16. Layer 14 is
comprised of bright nickel. The bright plate 13 is deposited by
4
CA 02193559 1999-11-23
conventional electroplating processes directly on the surface of
substrate 12.
Disposed on the nickel, preferably bright nickel layer 13 is
a relatively thin layer comprised of palladium. The palladium
strike layer 18 may be deposited on the nickel layer 13 by
conventional and well known palladium electroplating techniques.
Thus for example, the anode can be an inert platinized titanium
while the cathode is the substrate 12 having the nickel layer 13
thereon. The palladium is present in the bath as a palladium salt
or complex ion. Some of the complexing agents include polyamines
such as described in U.S. patent Nv. 4,486,274.
Some other palladium complexes such as palladium
tetra-amine complex used as the source of palladium in a number of
palladium electroplating processes are described in U.S. patent
Nos. 4,622,110; 4,552,628; and 4,628,165,
Same palladium electroplating
processes are described in U.S. patent Nos. 4,487,665; 4,491,507
and 4,545,869.
The palladium layer 18 generally has an average thickness of
at least about 0.25 millionths (0.00000025) of an inch, preferably
at least about 0.5 millionths (0.0000005) of an inch, and more
preferably at least about one millionth (0.000001) of an inch.
Generally, the upper range of thickness is not critical and is
determined by secondary considerations such as cost. However, the
thickness of~the palladium strike layer should generally not exceed
about 50 millionths (0.00005) of an inch, preferably 15 millionths
CA 02193559 1999-11-23
(0.000015) of an inch,'and more preferably 10 millionths (0.000010)
of an inch.
The ruthenium layer 20 is deposited on the palladium layer 18
in a variety of conventional and well known ways such as for
example by plating, sputtering, vacuum deposition, and depositing
the ruthenium metal as a finely divided dispersion in an organic
vehicle. The ruthenium is preferably deposited by plating,
preferably electroplating.
The ruthenium electroplating processes and plating baths are
conventional and well known. They are described, for example, in
the Journal of the Chemical Society of London, 1971 edition, page
839, by C.D. Burke and J.O. 0'Meardi and Electrodeposition of
Alloys, Vol. II, pp. 4-29, Abner Brenner (1963). The Ruthenium
electroplating baths may be acidic or nonacidic. Some illustrative
examples of nonacidic ruthenium electroplating baths are described
in U.S. Patent Nos. 4,297,178 and 4,507,183.
Some illustrative examples of
acid ruthenium plating baths are described in U.S. Patent No.
3,793,162. Some other ruthenium
plating baths are disclosed in U.S. Patent Nos.-3,576,724 and
4,377,448. The
ruthenium plating baths includes the nitrous salt baths and the
sulfamate baths.
The ruthenium may be electroplated by use of continuous direct
current densities or by use of pulse current plating, i.e., where
a current is generated for a first time period and is absent during
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CA 02193559 1999-11-23
a second time period, the first .and second time period reoccur
cyclically. Pulse current plating of ruthenium is described, for
example, in U.S. Patent No. 4,082,622,
The average thickness of the ruthenium layer 20 is at least
about 2 millionths (0.000002) of an inch, preferably at least about
millionths (0.000005) of an inch, and more preferably at leas t
about 8 millionths (0.000008) of an inch. The upper thickness
range is not critical and is generally dependent on economic
considerations. Generally, an average thickness of about 100
millionths (0.0001) of an inch, preferably about 75 millionths
(0.000075), and more preferably about 50 millionths (0.00005) of an
inch should not be exceeded.
Disposed over the ruthenium layer 20 is a layer 22 comprised
of a non-precious refractory metal such as hafnium, tantalum,
zirconium or titanium, preferably zirconium or titanium, and more
preferably zirconium.
Layer 20 serves, inter alia, to improve or enhance the
adhesion of layer 24 to layer 20. Layer 22 is deposited on the
ruthenium layer 20 by conventional and well known techniques such
as vacuum coating, physical vapor deposition such as ion
sputtering, and the like. Ion sputtering techniques and equipment
are disclosed, inter alia, in T. Van Vorous, "Planar Magnetron
Sputtering; A New Industrial Coating Technique", Solid State
Technology " Dec. 1976, pp 62-66; U. Kapacz and S. Schulz,
"Industrial Application of Decorative Coatings - Principle and
7
CA 02193559 1999-11-23
Advantages of the Sputter Ion Plating Process", Soc. Vac. Coat.,
Proc. 34th Ara. Techn. Conf., Philadelphia, U.S.A., 1991, 48-61;
and U.S. patent Nos. 4,162,954, and 4,591,418,
Briefly, in the sputter ion deposition process the refractory
metal such as titanium or zirconium target, which is the cathode,
and the substrate are placed in a vacuum chamber. The air in the
chamber is evacuated to produce vacuum conditions in the chamber.
An inert gas, such as Argon, is introduced into the chamber. The
gas particles are ionized and are accelerated to the target to
dislodge titanium or zirconium atoms. The dislodged target
material is then typically deposited as a coating film on the
substrate.
Layer 22 has a thickness which is at least effective to
improve the adhesion of layer 24 to layer 20. Generally, this
thickness is at Ieast about 0.25 millionths (0.00000025) of an
inch, preferably at least about 0.5 millionths (0.0000005) of an
inch, and more preferably at least about one millionth (0.000001)
of an inch. The upper thickness range is not critical and is
generally dependent upon considerations such as cost. Generally,
however, layer 22 should not be thicker than about 50 millionths
(0.00005) of an inch, preferably about 15 millionths (0.000015) of
an inch, and more preferably about 10 millionths (0.000010) of an
inch.
8
? ~ ~3~~~
In a preferred embodiment of the present invention layer 22 is
comprised of titanium or zirconium, preferably zirconium, and is
deposited by sputter ion plating.
Layer 24 is comprised of a hafnium compound, a tantalum
compound, a titanium compound or a zirconium compound, preferably
a titanium compound or a zirconium compound, and more preferably a
zirconium compound. The titanium compound is selected from
titanium nitride, titanium carbide, and titanium carbonitride, with
titanium nitride being preferred. The zirconium compound is
selected from zirconium nitride, zirconium carbonitride, and
zirconium carbide, with zirconium nitride being preferred.
Layer 24 provides wear and abrasion resistance and the desired
color or appearance, such as for example, of polished brass. Layer
24 is deposited on layer 22 by any of the well known and
conventional plating or deposition processes such as vacuum
coating, reactive sputter ion plating, and the like. The preferred
method is reactive ion sputter plating.
Reactive ion sputter is generally similar to ion sputter
deposition except that a reactive gas which reacts with the
dislodged target material is introduced into the chamber. Thus, in
the case where zirconium nitride is the top layer 24, the target is
comprised of zirconium and nitrogen gas is the reactive gas
introduced into the chamber. By controlling the amount of nitrogen
available to react with the zirconium, the color of the zirconium
nitride can be made to be similar to that of brass of various hues.
9
Layer 24 has a thickness at least effective to provide
abrasion resistance. Generally, this thickness is at least 2
millionths (0.000002) of an inch, preferably at least 4 millionths
(0.000004) of an inch, and more preferably at least 6 millionths
(0.000006) of an inch. The upper thickness range is generally not
critical and is dependent upon considerations such as cost.
Generally a thickness of about 30 millionths (0.00003) of an inch,
preferably about 25 millionths (0.000025) of an inch, and more
preferably about 20 millionths (0.000020) of an inch should not be
exceeded.
Zirconium nitride is the preferred coating material as it most
closely provides the appearance of polished brass.
In order that the invention may be more readily understood the
following example is provided. The example is illustrative and
does not limit the invention thereto.
EXAMPLE 1
Brass door escutcheons are placed in a conventional soak
cleaner bath containing the standard and well known soaps,
detergents, defloculants and the like which is maintained at a pH
of 8.9 - 9.2 and a temperature of 180 - 200oF for 30 minutes. The
brass escutcheons are then placed for six minutes in-a conventional
ultrasonic alkaline cleaner bath. The ultrasonic cleaner bath has
a pH of 8.9 - 9.2, is maintained at a temperature of about 160 -
180oF, and contains the conventional and well known soaps,
detergents, defloculants and the like. After the ultrasonic
cleaning the escutcheons are rinsed and placed in a conventional
~v
2 ~ 9 3 X59
alkaline electro cleaner bath for about two minutes. The electro
cleaner bath contains an insoluble submerged steel anode, is
maintained at a temperature of about 140 - 180oF, a pH of about
10.5 - 11.5, and contains standard and conventional detergents.
The escutcheons are then rinsed twice and placed in a conventional
acid activator bath for about one minute. The acid activator bath
has a pH of about 2.0 - 3.0, is at an ambient temperature, and
contains a sodium fluoride based acid salt. The escutcheons are
then rinsed twice and placed in a bright nickel plating bath for
about 24 minutes. The bright nickel bath is generally a
conventional bath which is maintained at a temperature of about 130
- 150oF, a pH of about 4.0 - 4.8, contains NiS04, NiCLz, boric acid,
and brighteners. A bright nickel layer of an average thickness of
about 750 millionths (0.00075) of an inch is deposited on the semi-
bright nickel layer. The bright nickel plated escutcheons are
rinsed three times and placed for about one and a half minutes in
a conventional palladium plating bath. The palladium bath utilizes
an insoluble platinized niobium anode, is maintained at a
temperature of about 95 - 140oF, a pH of about 3.7 - 4.5, contains
from about 1-5 grams per liter of palladium (as metal), and about
50-100 grams per liter of sodium chloride. A palladium layer of an
average thickness of about three millionths (0.000003) of an inch
is deposited on the bright nickel layer. The palladium plated
escutcheons are then rinsed twice.
11
2 ~ ~3~59
The palladium plated escutcheons are then placed into a
conventional ruthenium plating bath for about ten minutes. The
ruthenium bath utilizes insoluble platinized titanium anodes, is
maintained at a temperature of about 150-170 deg F, a pH of about
1.0-2.0, and contains about 3 grams per liter of ruthenium. A
ruthenium layer of an average thickness of about 10 millionths of
an inch is deposited over the palladium layer. The escutcheons are
then thoroughly rinsed and dried.
The ruthenium plated escutcheons are placed ir1 a sputter ion
plating vessel. This vessel is a stainless steel vacuum vessel
marketed by Leybold A.G. of Germany. The vessel is generally a
cylindrical enclosure containing a vacuum chamber which is adapted
to be evacuated by means of pumps. A source of argon gas is
connected to the chamber by an adjustable valve for varying the
rate of flow of argon into the chamber. In addition, two sources
of nitrogen gas are connected to the chamber by an adjustable valve
for varying the rate of flow of nitrogen into the chamber.
Two pairs of magnetron-type target assemblies are mounted in
a spaced apart relationship in the chamber and connected to
negative outputs of variable D.C. power supplies. ~ The targets
constitute cathodes and the chamber wall is an anode common to the
target cathodes. The target material comprises zirconium.
A substrate carrier which carries the substrates, i.e.,
escutcheons, is provided, e.g., it may be suspended from the top of
the chamber, and is rotated by a variable speed motor to carry the
substrates between each pair of magnetron target assemblies. The
12
219~~~9
carrier is conductive and is electrically connected to the negative
output of a variable D.C. power supply.
The ruthenium plated escutcheons are mounted onto the
substrate carrier in the sputter ion plating vessel. The vacuum
chamber is evacuated to a pressure of about 5x10'3 millibar and is
heated to about 400oC via a radiative electric resistance heater.
The target material is sputter cleaned to remove contaminants from
its surface. Sputter cleaning is carried out for about one half
minute by applying power to the cathodes sufficient to achieve a
current flow of about 18 amps and introducing argon gas at the rate
of about 200 standard cubic centimeters per minute. A pressure of
about 3x10'3 millibars is maintained during sputter cleaning.
The escutcheons are then cleaned by a low pressure etch
process. The low pressure etch process is carried on for about
five minutes and involves applying a negative D.C. potential which
increases over a one minute period from about 1200 to about 1400
volts to the escutcheons and applying D.C. power to the cathodes to
achieve a current flow of about 3.6 amps. Argon gas is introduced
at a rate which increases over a one minute period from about 800
to about 1000 standard cubic centimeters per minute, and the
pressure is maintained at about 1.1x10' millibars. The escutcheons
are rotated between the magnetron target assemblies at a rate of
one revolution per minute. The escutcheons are then subjected to
a high pressure etch cleaning process for about 15 minutes. In the
high pressure etch process argon gas is introduced into the vacuum
chamber at a rate which increases over a 10 minute period from
13
~? 9359
about 500 to 650 standard cubic centimeters per minute (i.e., at
the beginning the flow rate is 500 sccm and after ten minutes the
flow rate is 650 sccm and remains 650 sccm during the remainder of
the high pressure etch process), the pressure is maintained at
about 2x10'1 millibars, and a negative potential which increases
over a ten minute period from about 1400 to 2000 volts is applied
to the escutcheons. The escutcheons are rotated between the
magnetron target assemblies at about one revolution per minute.
The pressure in the vessel is maintained at about 2x10'1 millibar.
The escutcheons are then subjected to another low pressure
etch cleaning process for about five minutes. During this low
pressure etch cleaning process a negative potential of about 1400
volts is applied to the escutcheons, D.C. power is applied to the
cathodes to achieve a current flow of about 2.6 amps, and argon gas
is introduced into the vacuum chamber at a rate which increases
over a five minute period from about 800 sccm (standard cubic
centimeters per minute) to about 1000 sccm. The pressure is
maintained at about 1.1x10'2 millibar and the escutcheons are
rotated at about one rpm.
The target material is again sputter cleaned for about one
minute by applying power to the cathodes sufficient to achieve a
current flow of about 18 amps, introducing argon gas at a rate of
about 150 sccm, and maintaining a pressure of about 3x10'3
millibars.
14
21.93559
During the cleaning process shields are interposed between the
escutcheons and the magnetron target assemblies to prevent
deposition of the target material onto the escutcheons.
The shields are removed and a layer of zirconium having an
average thickness of about 3 millionths (0.000003) of an inch is
deposited on the ruthenium layer of the escutcheons during a four
minute period. This sputter deposition process comprises applying
D.C. power to the cathodes to achieve a current flow of about 18
amps, introducing argon gas into the vessel at about 450 sccm,
maintaining the pressure in the vessel at about 6x10'3 millibar, and
rotating the escutcheons at about 0.7 revolutions per minute.
After the zirconium layer is deposited a zirconium nitride
layer having an average thickness of about 14 millionths (0.000014)
of an inch is deposited on the zirconium layer by reactive ion
sputtering over a 14 minute period. A negative potential of about
200 volts D.C. is applied to the escutcheons while D.C. power is
applied to the cathodes to achieve a current flow of about 18 amps.
Argon gas is introduced at a flow rate of about 500 sccm. Nitrogen
gas is introduced into the vessel from two sources. One source
introduces nitrogen at a generally steady flow rate of about 40
sccm. The other source is variable. The variable source is
regulated so as to maintain a partial ion current of 6.3x10'11 amps,
with the variable flow of nitrogen being increased or decreased as
necessary to maintain the partial ion current at this predetermined
value.
~193~5~
The pressure in-the vessel is maintained at about 7.5x10'3
millibar.
The zirconium-nitride coated escutcheons are then subjected to
low pressure cool down, where the heating is discontinued, pressure
is increased from about 1.1x10'z millibar to about 2x10'1 millibar,
and argon gas is introduced at a rate of 950 sccm.
Although the present invention has been ~ described in
conjunction with a preferred embodiment, it is to be understood
that modifications and variations may be resorted to without
departing from the spirit and scope of the invention as those
skilled in the art will readily understand. Such modifications and
variations are considered to be within the purview and scope of the
invention and appended claims.
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