5,904,783 Method for reducing lead leaching in fixtures

Patent Number/Link:

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]

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u.s. Patent May 18, 1999

Fig. 1

Sheet 1 of 2 5,904,783

PRIOR ART

---2

u.s. Patent May 18, 1999 Sheet 2 of 2 5,904,783

Fig. 2

--8

(

5,904,783

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

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

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.

Immersion

Alloy Type Time (min)

cast untreated

cast 5

cast 15

cast 30

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

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.

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

* * * * *

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

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

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

temperature of said solution to less than about 1100 C.