5,904,783
May 18, 1999
[11]
[45]
111111111111111111111111111111111111111111111111111111111111111111111111111
US005904783A
Patent Number:
Date of Patent:
United States Patent [19]
Hager et al.
[54] METHOD FOR REDUCING LEAD
LEACHING IN FIXTURES
5,601,658 2/1997 Marinas et al. 148/553
OTHER PUBLICATIONS
References Cited
Assignee: Hazen Research, Inc., Golden, Colo.
Inventors: John P. Hager, Golden; Jerome P.
Downey, Parker, both of Colo.
AppI. No.: 08/936,264
Filed: Sep. 24, 1997
Int. C1.6 C22B 3/06
U.S. Cl. 148/242; 75/638; 75/710
Field of Search 75/743,710; 148/553,
148/242
ABSTRACT
A method for treating a brass fixture having a fluidcontacting
surface with lead dispersoids exposed thereon to
reduce lead leaching into a fluid supply by contacting the
brass fixture with a liquid metal solution selected from the
group consisting of a liquid sodium solution, a liquid potassium
solution and a liquid metal alloy solution to dissolve
lead dispersoids from the fixture, wherein the metal alloy
comprises a metal selected from the group consisting of
sodium and potassium.
23 Claims, 2 Drawing Sheets
[57]
Marinas et aI., Control of Drinking-Water Lead-Contamination
Contributed by Brass Plumbing Fixtures, Proc. 1993
Am. Waterworks Assoc. Ann. Conf, pp. 945-971. No Month.
Primary Examiner~rince Willis
Assistant Examiner-Tima M. McGuthry-Banks
Attorney, Agent, or Firm---8heridan Ross P.e.
11/1989 Rushton.
8/1992 McDivitt.
10/1995 Downey.
8/1996 Coltrinari et al. .
U.S. PATENT DOCUMENTS
4,879,094
5,137,685
5,454,876
5,544,859
[56]
[73]
[75]
[21]
[22]
[51]
[52]
[58]
10 ,
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16
u.s. Patent May 18, 1999
Fig. 1
Sheet 1 of 2 5,904,783
4
PRIOR ART
---2
u.s. Patent May 18, 1999 Sheet 2 of 2 5,904,783
Fig. 2
10
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(
14
16
5,904,783
2
SUMMARY OF THE INVENTION
DETAILED DESCRIPTION OF THE
INVENTION
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention provides a method for removing
lead from a fixture used in conducting the flow of fluids such
as water, thus inhibiting the leaching of lead into the fluid.
The invention is applicable to pipes, valves, faucets, pumps
The present invention provides a method for treating a
brass fixture having a fluid-contacting surface with lead
dispersoids exposed thereon to reduce lead leaching into
water supplies. The method comprises contacting the brass
fixture with a liquid metal solution to dissolve at least a
portion of the lead dispersoids, and removing the brass
fixture from the solution. Typically, a liquid metal solution
at a temperature from about 1500 C. to about 2500 C. is used
to dissolve the lead dispersoids. The liquid metal solution
includes sodium, potassium or metal alloys which include
sodium and/or potassium.
The invention further provides contacting a brass fixture
which has been immersed in the liquid metal bath with a
neutralizing solution. Typically, any liquid metal solution
material remaining on the brass fixture is quenched by
immersing the brass fixture in a solution containing a
mixture of alcohol and water.
The invention further provides a method of neutralizing
the resulting alkaline solution of a metal alkoxide and/or
metal hydroxide by quenching the basic solution with an
acid. Preferably, hydrochloric acid is used to neutralize the
alkaline solution. This quenching results in formation of
harmless products composed of water and a metal chloride,
for example, sodium chloride and/or potassium chloride.
The invention further provides a method of removing the
lead dissolved in the liquid metal bath by lowering the
temperature of the bath to about 1100 C. which causes solid
lead to precipitate out of the solution. This method provides
a facile separation of lead from the liquid metal solution
simply by removing the solid lead from the solution.
Typically, the liquid metal solution used to dissolve the lead
dispersoids is at temperatures from about 1500 C. to about
2500 C.
The present invention is applicable for removing lead
from any brass item including, but not limited to a plumbing
fixture or a device for fluid storage and transportation such
as pipe, faucet, valve and pump.
FIG. 1 depicts a cross-sectional view of a pipe or plumbing
fixture capable of storing or transporting potable water
or other fluids.
FIG. 2 is an expanded cross-sectional view depicting the
conduit surface, perimeter portion, continuous solid phase,
60 second solid phase, and voids.
from reaching equilibrium. This process generates a waste
solution which cannot be simply discarded but requires
special disposal methods.
Therefore, despite the developments made in the area of
reduced lead leaching into potable water systems, there
remains a need to provide a material which is less susceptible
to leaching lead into potable water systems, yet which
utilizes the inherent benefits of copper alloys that contain
lead, and for a process of removing lead from brass fixtures
10 which does not generate wastes that require special disposal
methods.
FIELD OF THE INVENTION
1
METHOD FOR REDUCING LEAD
LEACHING IN FIXTURES
BACKGROUND OF THE INVENTION
Potable water systems are comprised of numerous components
including pipe and plumbing fixtures such as
faucets, valves, couplings, and pumps which both store and
transport water. These components have traditionally been
made of copper-based cast and wrought alloys with lead
dispersed therein in amounts between 1-9% by weight. The 15
lead allows these components to be more easily machined
into a final product which has both a predetermined shape
yet acceptable strength and watertight properties.
The lead used to improve the machinability of these
copper alloy materials has been proven to be harmful to 20
humans when consumed as a result of the lead leaching into
potable water. This damage is particularly pronounced in
children with developing neural systems. To reduce the risk
of exposure to lead, federal and state governments now
regulate the lead content in potable water by requiring 25
reductions in the amount of lead which can leach from
plumbing fixtures. A variety of strategies have been developed
to address this problem. For example, simply reducing
the amount of lead in plumbing fixtures has been attempted.
However, such low lead content alloys are difficult to 30
machine.
Another strategy is to develop specific alloys such as that
disclosed in U.S. Pat. No. 4,879,094 to Rushton. The patent
describes an alloy which contains 1.5-7% bismuth, 5-15% 35
zinc, about 1-12% tin and the balance copper. This copper
alloy is capable of being machined, but must be cast and not
wrought. This is undesirable since a wrought alloy may be
extruded or otherwise mechanically formed into shape. It is
thus not necessary to cast objects to a near finished shape. 40
Further, wrought alloy feed stock is more amenable to high
speed manufacturing techniques and generally has lower
associated fabrication costs than cast alloys.
A copper based machinable alloy with a reduced lead
content or which may be lead free was disclosed by McDi- 45
vitt in U.S. Pat. No. 5,137,685. This alloy contains from
about 30-58% by weight zinc, 0-5% weight of bismuth, and
the balance of the alloy being copper. This alloy is expensive
to produce, however, based both on the cost of the bismuth
as compared to lead, and further since the bismuth must be 50
thoroughly mixed within the matrix of the copper alloy
material.
Another approach to inhibiting lead leaching in water
involves non-continuous coating of lead dispersoids in the
brass fixture as described by Coltrinari et al. in U.S. Pat. No. 55
5,544,859. The patent describes a method and apparatus for
selectively coating lead dispersoids with, e.g., tin or
bismuth, thereby reducing the amount of lead exposed to the
liquid conduit. This coating results in lower lead leaching
into the liquid.
Yet another approach involves treating brass plumbing
components with an aqueous solution containing a desired
concentration of chloride and pyrophosphate as described by
Downey in U.S. Pat. No. 5,454,876. The patent discloses a
method for promoting dissolution of lead by chlorine ion 65
and sequestering the dissolved lead in the solution by
pyrophosphate ion to prevent the lead dissolution reaction
5
The present invention relates to a method for removing
lead from a brass fixture containing lead dispersoids.
5,904,783
3 4
present process. Because the liquid metal solution is applied
to the surface of the solid body piece 2 or only to the conduit
surface 4 of the solid body piece 2 voids do not occur
uniformly throughout the solid body piece 2. As used in this
5 invention, "liquid metal solution" refers to a metal or an
alloy in a liquid state and includes a pure liquid metal as well
as liquid metal containing impurities.
In one embodiment of the present invention, the brass
fixture having a fluid-contacting surface with lead disper-
10 soids exposed thereon is contacted with liquid metal solution
to dissolve at least a portion of the lead dispersoids. The
resulting brass fixture has a lower capacity for lead leaching
into fluids, such as water, carried thereby than does on an
untreated fixture. Preferably the liquid metal bath (i.e.,
solution) removes at least about 50% by weight of the
15 surface lead dispersoids, more preferably at least about 75%
by weight, and most preferably at least about 90% by
weight. In another aspect of the present invention, the
surface area of the second solid phase of lead dispersoids
exposed on the conduit surface 4 is removed by at least
20 about 90% by the method of the present invention. In a more
preferred embodiment, the surface area of the second solid
phase of lead dispersoids 10 exposed on the conduit surface
4 is reduced by at least about 95% and in a most preferred
embodiment, at least about 99%.
Any liquid metal or alloy which has a relatively low
melting point and selectivity to dissolve significantly more
lead in the presence of copper can be used in the present
invention as an immersion bath for removing lead from a
brass fixture. A useful immersion bath include, but are not
30 limited to, a liquid sodium, a liquid potassium and a liquid
alloy containing sodium and/or potassium.
Liquid sodium has been used in variety of areas, including
passivating the surface of polytetrafluoroethylene (Teflon)
for the acceptance of adhesives. See page 6 of a product
35 pamphlet published by Du Pont entitled "Sodium Properties,
Uses Storage, and Handling." Sodium metal melts at about
97.8° C. At this temperature, only a trace amount of lead
dissolves in liquid sodium. As the temperature is gradually
increased, solubility of lead in liquid sodium increases. At
40 around 200° c., up to about 20% by weight of lead may be
dissolved in liquid sodium. With increases in temperature,
however, the solubility of other metals also increases correspondingly.
Thus, a temperature of liquid sodium preferred
for selective removal of lead from a brass fixture is
45 greater than about 110° c., more preferably greater than
about 150° c., and most preferably greater than about 200°
C. A preferred range of liquid sodium temperature is
between about 110° C. and about 275° c., more preferably
between about 150° C. and about 250° c., and most pref-
50 erably between about 175° C. and about 225° C.
Liquid potassium metal melts at about 63.5° C. Even at
this temperature, about 10% by weight of lead dissolves in
liquid potassium. As the temperature is gradually increased,
solubility of lead in liquid sodium increases. At around 200°
55 c., up to about 30% by weight of lead may be dissolved in
liquid potassium. With increases in temperature, however,
the solubility of other metals also increases correspondingly.
Thus, a temperature of liquid potassium preferred for selective
removal of lead from a brass fixture is greater than about
60 80° c., more preferably greater than about 150° c., and most
preferably greater than about 200° C. A preferred range of
liquid potassium temperature is between about 100° C. and
about 275° c., more preferably between about 150° C. and
about 250° c., and most preferably between about 175° C.
65 and about 225° C.
A metal alloy comprising potassium and sodium have
much lower melting point than either of the pure metals. For
and other commonly known plumbing fixtures. The materials
typically used in the production of these plumbing
fixtures include copper alloys, such as brass, which have
lead dispersed throughout the alloy material.
As shown in FIGS. 1 and 2, a fixture produced by the
process of the present invention includes a solid body piece
2 having voids 12. The flow directing or solid body piece 2
is shaped such that it has a conduit surface 4 which substantially
defines a conduit volume 6. The conduit volume 6
is the space through which the apparatus is designed to have
fluid flow. For example, in the instance where the apparatus
is a pipe, the conduit surface 4 is the inside surface of the
pipe, which contacts water flowing through the pipe on the
fluid contact or conduit surface 4.
The solid body piece 2 includes a continuous solid phase
8 and a second solid phase 10 within the continuous solid
phase 8. For instance, in the case of a brass pipe having lead
dispersoids throughout the brass, the brass is the continuous
solid phase 8 and the lead constitutes the second solid phase
of dispersoids 10.
The continuous solid phase 8 is typically metal and more
typically comprises copper. For example, the continuous
solid phase 8 can be a copper alloy and can contain over 50%
by weight of copper. Such copper alloys can be brass 25
including Cu/Zn/Si; Mn bronze; leaded Mn bronze and a
variety of bronzes including Cu/Sn; Cu/Sn/Pb; Cu/Sn/Ni;
Cu/AI; and other high copper alloys containing 94-98.5
weight percent Cu and 0.02 weight percent lead. The alloys
typically include between about 50 weight percent and about
98.5 weight percent Cu, more preferably between about 53.5
weight percent and about 94 weight percent Cu and more
preferably between about 60 weight percent and about 82
weight percent Cu. In a preferred embodiment of the present
invention, a continuous solid body phase comprised of about
57%-82% copper, 0.2% tin, 7%-41% zinc, 2%-8% lead,
and trace amounts of iron, antimony, nickel, sulfur,
phosphorous, aluminum and silicon is used.
The second solid phase of dispersoids 10 comprise lead.
The lead dispersoids are dispersed in the continuous solid
phase 8 and a plurality are adj acent the fluid contact or
conduit surface 4. Thus, while the lead dispersoids are
contained throughout the interior matrix of the continuous
solid phase 8, some portion can be exposed on the fluid
contact or conduit surface 4. Therefore, untreated solid body
pieces 2 having lead exposed to fluids flowing throughout
the conduit volume 6 allow for the leaching of lead into the
fluid, which may contaminate the fluid. Typically, lead
dispersoids approximately comprise 1-9% by weight of the
solid body piece 2 and more typically 3-5%. In one
embodiment, the second solid phase of dispersoids 10 consists
essentially of lead. The plurality of lead dispersoids
allows the solid body piece 2 to be machined more easily
and allows for the use of wrought alloy feed stock rather
than cast alloy components.
In accordance with the method of the present invention, as
described fully below, a treated apparatus also includes
multiple voids 12 at the conduit surface 4. The voids 12 are
formed by removal of lead dispersoids occurring at the
conduit surface 4 by the present process.
In another embodiment of the apparatus produced by the
method of the present invention, the solid body piece 2
comprises a perimeter portion 14 which includes the conduit
surface 4 and an interior portion 16 which is integral with the
perimeter portion 14. The interior portion 16 does not
include the conduit surface 4. Dispersoids in the interior
portion 16 of the solid body piece 2 are not subject to the
5,904,783
5 6
The effectiveness of the present invention can be quantitatively
measured in various ways. For example, the percent
removal of lead dispersoids exposed on the surface of a fluid
conduit can be measured, for example by electron microscopic
techniques, or ZAP-corrected analysis. As used in
this invention, a "ZAP-corrected analysis" refers to a semiquantitative
analysis obtained via electron microscopic technique
which accounts for the atomic number (Z), atomic
weight (A) and fluorescence (F) effects of the element being
analyzed. The technique is well-known by one skilled in the
art of electron microscopy. In addition, the effectiveness of
the present invention in reduction of lead leaching into water
can be quantitatively measured by tests which measure the
amount of lead in water which has been allowed to stand in
contact with a fixture under standardized conditions. For
example, one standardized procedure has been established
by the National Sanitation Foundation and is known as the
National Sanitation Foundation 61 ("NSF-61") procedures.
More specifically, Section 9 of the NSF-61 publication
discusses the procedure for testing mechanical plumbing
devices and components.
The NSF-61 standardized procedure requires the triplicate
testing of mechanical plumbing fixtures, wherein samples
are rinsed with tap water at room temperatures, then filled
with water at various temperatures for periods of time up to
90 days. The contaminant level of lead which has leached
into the water from the fixture is then quantitatively measured
to gauge the lead leaching characteristics of the
particular plumbing apparatus or fixture. This procedure is
discussed in detail by Coltrinari et aI., in U.S. Pat. No.
5,544,859, which is incorporated herein in its entirety.
Untreated wrought brass alloys normally obtain a NSF-61
score of about 10 microgramslliter when the alloy is exposed
to water for a period of 1 day. Thereafter, the concentrations
of lead falls within the range of 3-6 microgramslliter during
subsequent days of testing. Similarly, typical NSF-61 scores
for untreated cast brass ranges from about 50-55
microgramslliter after exposure to water for 1 day, declining
to about 38 microgramslliter on day 2, and ranging from
about 13-25 microgramslliter for subsequent days of testing.
A further embodiment of the present invention includes
recovering lead from the liquid metal solution by lowering
the temperature of the liquid metal bath to decrease the
45 solubility of lead in the liquid metal solution, preferably to
a temperature of less than about 110° c., and more preferably
less than about 80° C. One of the advantages of a
temperature dependant solubility of lead in a liquid metal
solution is the ease of purification of the resulting liquid
metal solution. Lowering the temperature of liquid metal
solution containing dissolved lead to about 110° C. results in
precipitation of solid lead which can be easily separated
from the liquid metal solution by any of the standard
techniques known in separating a solid from a liquid, such
as filtration, sedimentation/decantation and centrifuging.
In a further embodiment, this "purified", i.e., separated,
liquid metal solution can be recycled and used again to
dissolve lead from another brass fixture by reheating the
liquid metal solution and contacting it with a brass fixture.
A further embodiment of removing lead from a brass
fixture having a fluid-contacting surface with lead dispersoids
exposed thereon by contacting with a liquid metal
solution is neutralization of liquid metal solution material
present in the brass fixture after it has been removed from
the liquid metal solution. As used in this invention, "liquid
metal solution material" refers to the metal or alloy which is
used as the liquid metal solution to dissolve lead. Depending
example, at the eutectic point (76.7% by weight of
potassium) the metal alloy melts at about -12.5° C.
Therefore, if a lower temperature is desired for the removal
of lead dispersoids in a brass fixture, one skilled in the art
can easily determine the desired potassium-sodium compo- 5
sition for a particular temperature range desired.
It is preferred that the temperature of liquid metal, and
other process conditions, provide for dissolution of a high
amount of lead while maintaining dissolution of a low
amount of other metals such as copper and zinc which are 10
also present in a brass fixture so that lead is selectively
removed. Preferably, the step of contacting a brass fixture
with the liquid sodium bath is conducted under conditions
such that the individual concentration of other metals from
the brass fixture, such as copper and zinc, is maintained at 15
a concentration in the liquid metal bath below about 10% by
weight, more preferably below about 5% by weight, and
most preferably below about 2.5% by weight.
In another embodiment of the present invention, the brass
fixture having a fluid-contacting surface with lead disper- 20
soids exposed thereon is contacted with a liquid metal
solution for a time adequate to substantially remove lead
from the brass fixture. Preferably the brass fixture is contacted
with a liquid metal solution for at least about 5
minutes, more preferably for at least about 15 minutes, and 25
most preferably for at least about 30 minutes.
In another embodiment of the present invention, the brass
fixture having a fluid-contacting surface with lead dispersoids
exposed thereon is contacted with a sufficient volume
of the liquid metal solution to substantially remove surface 30
lead dispersoids from the brass fixture under a given time
and temperature of the liquid metal solution. Preferably, the
volume of the liquid metal solution is sufficient to completely
immerse a portion of the brass fixture to be treated by
the present invention. More preferably, the volume of the 35
liquid metal is sufficiently large enough to treat many
fixtures in the bath, preferably in continuous mode. In some
cases, it may be necessary or even desirable to frequently
purify the liquid metal bath to help ensure that the solubility
limit for lead is not exceeded. The exact amount of liquid 40
metal solution required depends on many factors such as
immersion bath operating temperature, the solubility of lead
in a given liquid metal solution, the amount of lead in the
untreated brass fixtures, and the number of brass fixtures
treated per unit of time.
The present invention can be used to remove substantially
all surface lead dispersoids or substantially only those
surface lead dispersoids on the conduit surface which the
apparatus is designed to have fluid flow. For example, a
complete immersion of the brass fixture in a liquid metal 50
solution provides substantial removal of all surface lead
dispersoids, whereas contacting only the conduit surface of
the brass fixture with a liquid metal solution results in
substantial removal of lead dispersoids only on the conduit
surface of the brass fixture. Selective lead removal from the 55
conduit surface can be achieved by pouring the liquid metal
solution into the conduit of the brass fixture or allowing a
continuous flow of a liquid metal solution through the
conduit of the brass fixture.
In another embodiment of the present invention, an effec- 60
tive amount of lead is removed from the brass fixture having
a fluid-contacting surface with lead dispersoids exposed
thereon by contacting the brass fixture with a liquid metal
solution to provide a brass fixture having an amount of lead
acceptable for health reasons to provide safe drinking sup- 65
plies and/or to meet applicable federal or state governmental
regulations.
5,904,783
7 8
Comments
BEl-Significant amount of lead
was present.
BEI-Lead removal was efficient
for lead dispersoids but not for
"smeared" lead.
BEl-Surface lead depleted in the
area that was immersed in the
liquid sodium solution.
BEI-A zone of residual surface
lead remained, but otherwise
lead removal efficiency was
high.
BEl-Surface lead depleted in the
area that was in contact with
the liquid sodium solution.
BEI-Liquid sodium solution
treated portion of the brass
coupon had significantly less
amount of surface lead than
untreated portion of the brass
coupon.
BEl-Substantial elimination of
lead on flat surface of a
wrought coupon.
TABLE 1
wrought 60
Results of Different Alloy Brass Coupon Immersions in a 200 0 C.
Liguid Sodium Solution at Different Time Intervals
Example 1
This Example illustrates the effect of the present invention
on wrought and cast brass at various immersion times.
Brass coupons were partially immersed in a liquid sodium
solution in accordance with the standard procedure
described above. The temperature of the liquid sodium bath
was 200° C. Tests were conducted with wrought and cast
alloy types with immersion times of 5, 15, 30, 60 and 120
minutes. The results are shown below in Table 1.
In general, immersion of the samples in liquid sodium
effectively removed the surface inclusions of lead. Many of
the backscattered electron images illustrated a clear transition
evident between the portion of each sample that was
immersed in the liquid sodium and that which was not.
Example 2
This Example illustrates the effect of the practice of the
present invention on brass having different surface irregu1arities.
35
Immersion
Alloy Type Time (min)
cast untreated
cast 5
40
cast 15
cast 30
45
cast 60
50 cast 120
a container pending scanning electron microscopic examination.
Precautions are taken to avoid accidental contamination
of the treated coupons. At the conclusion of the tests,
the liquid sodium is drained from the melting furnace into a
5 prepositioned graphite mold and allowed to solidify. The
melting pot and chamber are cleaned with the propanol and
water mixture.
It should be noted that after melting, the liquid sodium
typically has a relatively thin, white to blue-white, oxide
layer on its surface. When the first coupon is inserted into a
10 fresh melt, the oxide layer around the coupon obtains a brass
coloration. Generally, the treated coupons retain a thin layer
of oxide and/or metallic sodium prior to immersion in
alcohol water mixture. Caution should be exercised when
immersing the treated coupon into an alcohol water mixture
15 as a violent reaction may occur.
The procedure's effectiveness is determined by electron
microprobe evaluation. A scanning electron microprobe
(SEM) is used to produce backscattered electron images
(BEl) of the surfaces of the as-received and treated samples.
Also, some samples were analyzed by ZAP-corrected analy-
20 sis (ZAP).
on the temperature, the liquid metal solution material, which
is present in the brass fixture after it has been removed from
the liquid metal solution, can be a liquid or a solid. It is
preferred that after contacting the brass fixture with a liquid
metal solution to dissolve lead dispersoids as generally
described herein, the brass fixture is removed from the liquid
metal solution and any liquid metal solution material
remaining on the brass fixture is neutralized with a neutralizing
solution. Preferably, the neutralizing solution comprises
a solvent having a proton source, more preferably the
solvent comprises a mixture of alcohol and water. Alcohols
which are useful in neutralizing solid or liquid sodium
include, but are not limited to, methanol, ethanol, propanol,
i-propanol, n-butanol, i-butanol, t-butanol, pentanol,
hexanol, heptanol, and octanol.
When liquid metal solution material is treated with alcohol
and/or water, a metal alkoxide and/or a metal hydroxide
is formed, respectively, as a reaction product. This basic
metal salt can be neutralized with an acid such as hydrochloric
acid, sulfuric acid, phosphoric acid, hydriodic acid,
hydrobromic acid or a carboxylic acid, such as acetic acid.
Preferably, hydrochloric acid is used to neutralize the resulting
metal alkoxide and/or metal hydroxide. The use of
hydrochloric acid results in formation of water and metal
chloride, e.g., sodium chloride and/or potassium chloride, as 25
the reaction products which are environmentally safe and
can be readily disposed of without any need for a special
treatment.
The present method of lead removal is applicable to
variety of plumbing fixtures or devices for fluid storage and 30
transportation including, but not limited to, pipes, faucets,
valves, and pumps.
The following examples are provided for the purposes of
illustration and are not intended to limit the scope of the
present invention.
EXAMPLES
Standard Procedure
A standard experimental procedure for treating brass
materials in accordance with the present invention is provided
below.
Solid sodium metal is added to a melting furnace
("chamber") to produce a liquid sodium bath depth sufficient
to immerse brass coupons to simulate a sample of a brass
fixture. The size of the bath container is selected to provide
sufficient freeboard to preclude a possibility of a sodium
spill. After the test coupons are positioned in the chamber,
the chamber access door is closed and sealed. The chamber
is flushed with nitrogen, and an inert atmosphere of nitrogen
is maintained throughout the experiment. It should be cautioned
that sodium metal reacts violently with any moisture
in atmosphere and ignites in air at about 120° C.
The sodium bath temperature is gradually increased to a
desired target temperature. Once the liquid sodium bath is 55
stabilized to a desired temperature, the first coupon is
immersed in the bath for the prescribed period of time. After
the immersion for a desired period of time, the coupon is
removed and held just above the bath to allow excess sodium
to drip off before proceeding with the next coupon in the 60
series. After the last coupon in the series is treated, the bath
temperature is lowered to about 110° C. The chamber is
opened for recovery of the treated coupons. The treated
coupons are removed from the chamber and residual sodium
is washed off the treated coupons by immersing them in a 65
4:1 mixture of propanol and water. Each treated coupon is
tagged with a label detailing the test conditions and stored in
5,904,783
9 10
65
backscattered electron image of the treated specimen. The
ZAP-corrected analysis indicated presence of 5.9% lead.
The difference in response to the experiment may possibly
be a result of much rougher surface of the casting.
Example 3
This Example illustrates the practice of the present invention
at different liquid sodium solution temperatures.
At 3000 c., lead can be dissolved in liquid sodium to form
a liquid alloy containing approximately 40% lead by weight,
10 or about double the amount compared to liquid sodium at
2000 C.
Four types of brass coupons were treated in accordance
with the Standard Procedure described above: the cast and
wrought coupons, flat (unpolished) control coupons, and
15 cylinder segments. Samples of each brass coupon type were
immersed in liquid sodium at 3000 C. for 5 or 15 minutes.
A significant discoloration was observed on the treated
samples following the immersion tests at 3000 c.; each
sample had a very dark blue-grey tint after the treatment.
The discoloration was most obvious on the wrought coupon
20 and test cylinder sections.
Electron microprobe evaluation and ZAF-corrected
analysis suggested that the other metals, such as copper and
zinc, were also being dissolved in significant amounts at
3000 C. Consequently, substantial surface lead remained
exposed in the treated specimens. According to the ZAPcorrected
analysis, the lead content of all specimens treated
at 3000 C. was 2.8% or higher.
Those skilled in the art will appreciate that numerous
changes and modifications may be made to the preferred
embodiments of the present invention and that such changes
and modifications may be made without departing from the
spirit of the invention. It is therefore intended that the
appended claims cover all such equivalent variations as fall
within the true spirit and scope of the invention.
What is claimed is:
1. A method for treating a brass fixture having a fluidcontacting
surface with lead dispersoids exposed thereon to
reduce lead leaching into a fluid supply, said method comprising:
(a) contacting said brass fixture with a solution to dissolve
at least a portion of said lead dispersoids, wherein said
solution comprises a metal in the liquid state, and
wherein said metal is selected from the group consisting
of sodium, potassium, and mixtures thereof; and
(b) removing said brass fixture from said solution.
2. The method of claim 1, wherein the temperature of said
solution during said step of contacting is between about 1500
C. and about 2500 C.
3. The method of claim 1, wherein the temperature of said
50 solution is greater than about 2000 C.
4. The method of claim 1, further comprising the step of
recovering lead from said solution.
5. The method of claim 4, wherein said step of recovering
lead from said solution comprises lowering the temperature
55 of said solution to less than about 1100 C.
6. The method of claim 4, wherein said recovery of said
lead comprises precipitating said lead from said solution.
7. The method of claim 6, further comprising separating
said precipitated lead from said solution and contacting said
60 separated solution with a brass fixture to dissolve at least a
portion of said lead dispersoids therein.
8. The method of claim 1, wherein said liquid metal
solution has a copper concentration of less than about 2.5%
by weight.
9. The method of claim 1, wherein said liquid metal
solution has a zinc concentration of less than about 2.5% by
weight.
TABLE 2
Effect of Relative Surface Roughness of Brass in Removal of
Lead by a Liguid Sodium Solution at 200 0 C.
Immersion
Alloy Type Time (min) Comments
untreated N/A BEl-Significant amount of lead 25
control was present.
wrought
brass CDA
36000
polished 30 BEl-The surface of the specimen
wrought was devoid of lead. 30
brass ZAF-No lead detected.
CDA 36000
polished 5 BEl-Sample was devoid of lead.
wrought ZAF-0.7% lead present.
brass
CDA 36000
wrought 30 BEl-No surface lead was evident. 35
brass CDA ZAF-0.6% lead present.
36000
cast brass 30 BEl-Significant amount of lead
CDA84400 was present.
ZAF-5.9% lead present.
40
Four types of brass specimen coupons were treated in
accordance with the Standard Procedure described above:
cast (CDA84400), wrought (CDA36000), polished wrought
brass (CDA36000) as control samples, and a section of a test
cylinder (CDA 36000). The above designations refer to the 5
Copper Development Association (CDA) numbers for the
two brass types that were used in the present testing. The
polished control samples were tested to provide a basis for
comparison in determining the effect of the surface irregularities
common to the other types of sample. It should be
also noted that wrought brass samples were generally much
smoother than the cast brass samples.
One specimen from each of the four coupon types was
immersed for 30 minutes in a 2000 C. liquid sodium. A
five-minute immersion test was also conducted on a duplicate
of the polished control sample. The results are shown
below in Table 2.
Metallographic techniques and electron microprobe
evaluation were used to evaluate each treated specimen. The
back scattered electron images of the specimens revealed
very little lead remained on the surface after treatment. The 45
ZAP-corrected analysis of the specimens confirmed this
fact.
The results of this example indicate that the treatment
method appears to be influenced by the surface morphology
of a particular sample, e.g., the more even the surface, the
more effective the lead removal. The best result was
obtained with the control specimen with the polished surface.
No lead could be detected in the backscattered electron
image of the polished control coupon that was immersed for
30 minutes, and the ZAP-corrected analysis showed no lead
was present. Based on visual evidence, the control coupon
that was immersed for only 5 minutes also resulted in nearly
total lead removal, as no lead was evident in the backscattered
electron images. However, the ZAP-corrected analysis
for this specimen indicated presence of 0.7% lead. The
difference in immersion time could conceivably account for
the slight amount of lead detected in the five-minute specimen.
Similarly, no surface lead was evident in the wrought
coupon, but the ZAP-corrected analysis indicated presence
of 0.6% lead.
The technique was not as effective with the cast coupon.
Several lead inclusions were visible on the photograph of the
5,904,783
11 12
* * * * *
20
19. The method of claim 18, wherein said liquid metal
solution has a copper concentration of less than about 2.5%
by weight.
20. The method of claim 18, further comprising removing
5 solution material from said brass fixture by contacting said
brass fixture containing said solution material with a neutralizing
solution.
21. A method for treating a brass fixture having a fluidcontacting
surface with lead dispersoids exposed thereon to
reduce lead leaching into a fluid supply, said method com10
prising:
(a) contacting said brass fixture with a solution at a
temperature between about 1500 C. and about 2500 C.
to dissolve at least a portion of said lead dispersoids,
wherein said solution comprises a metal in the liquid
state, and wherein said metal is selected from the group
consisting of sodium, potassium, and mixtures thereof;
(b) removing said brass fixture from said solution; and
(c) removing solution material from said brass fixture by
contacting said brass fixture with a neutralizing solution.
22. The method of claim 21, wherein said neutralizing
solution comprises a mixture of an alcohol and water.
23. A method for treating a brass fixture having a fluidcontacting
surface with lead dispersoids exposed thereon to
25 reduce lead leaching into a fluid supply, said method comprising:
(a) contacting said brass fixture with a liquid sodium
solution at a temperature between about 1500 C. and
about 2500 C. to dissolve at least a portion of said lead
dispersoids;
(b) removing said brass fixture from said liquid sodium
solution; and
(c) removing sodium from said brass fixture by contacting
said brass fixture with a solution comprising an alcohol
and water.
10. The method of claim 1, further comprising removing
solution material from said brass fixture by contacting said
brass fixture containing said solution material with a neutralizing
solution.
11. The method of claim 10 wherein said neutralizing
solution comprises a solvent having a proton source.
12. The method of claim 11 wherein said solvent comprises
a mixture of an alcohol and water, and wherein said
step of contacting said brass fixture with said neutralizing
solution produces a metal hydroxide and/or a metal alkoxide.
13. The method of claim 12, wherein said metal hydroxide
and/or metal alkoxide is reacted with an acid to form said
alcohol and/or water and a metal salt.
14. The method of claim 13 wherein said acid is hydro- 15
chloric acid.
15. The method of claim 1, wherein said brass fixture
comprises a brass fixture selected from the group consisting
of a plumbing fixture, a piping piece, a faucet, a valve and
a pump.
16. The method of claim 1, wherein said solution comprises
liquid sodium.
17. The method of claim 1, wherein said solution comprises
liquid potassium.
18. A method for treating a brass fixture having a fluidcontacting
surface with lead dispersoids exposed thereon to
reduce lead leaching into a fluid supply, said method comprising:
(a) contacting said brass fixture with a solution at a
temperature between about 1500 C. and about 2500 C. 30
to dissolve at least a portion of said lead dispersoids,
wherein said solution comprises a metal in the liquid
state, and wherein said metal is selected from the group
consisting of sodium, potassium, and mixtures thereof;
(b) removing said brass fixture from said solution; and 35
(c) recovering lead from said solution by lowering the
temperature of said solution to less than about 1100 C.