U.S. patent application number 10/186893 was filed with the patent office on 2002-11-21 for method of reducing elution of lead in lead-containing copper alloy, and drinking water service fittings made of lead-containing copper alloy.
Invention is credited to Gotou, Akira, Imamoto, Mituo, Kawamoto, Masashi.
Application Number | 20020170632 10/186893 |
Document ID | / |
Family ID | 26531729 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020170632 |
Kind Code |
A1 |
Kawamoto, Masashi ; et
al. |
November 21, 2002 |
Method of reducing elution of lead in lead-containing copper alloy,
and drinking water service fittings made of lead-containing copper
alloy
Abstract
It is an object of the present invention to provide a processing
method for preventing elution of lead in a lead-containing copper
alloy to prevent lead from eluting from a faucet metal, etc. made
of a lead-containing copper alloy, and a drinking water service
fitting made of a lead-containing copper alloy in which elution of
lead has been prevented. By forming a chromate film on the surface
of a lead-containing copper alloy material, it is possible to
reduce elution of the lead left in a limited amount on the surface.
A drinking water service fitting made of a lead-containing copper
alloy is immersed in an alkaline etching solution in a
pre-processing step for a nickel chromium plating step to
selectively remove lead on the surface of the lead-containing
copper alloy material and is then activated in a solution such as
sulfuric acid and hydrochloric acid. Nickel plating is subsequently
effected, and then chromium plating is effected in a sargent
chromium or chromium fluoride bath, and a chromate film may be
formed by immersing the drinking water service fitting in a
chromate solution.
Inventors: |
Kawamoto, Masashi;
(Kita-kyushu-shi, JP) ; Gotou, Akira;
(Kita-kyushu-shi, JP) ; Imamoto, Mituo;
(Kita-kyushu-shi, JP) |
Correspondence
Address: |
SHAW PITTMAN LLP
1650 TYSONS BOULEVARD
McLEAN
VA
22102
US
|
Family ID: |
26531729 |
Appl. No.: |
10/186893 |
Filed: |
July 2, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10186893 |
Jul 2, 2002 |
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09586608 |
Jun 2, 2000 |
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09586608 |
Jun 2, 2000 |
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PCT/JP98/05429 |
Dec 2, 1998 |
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Current U.S.
Class: |
148/254 |
Current CPC
Class: |
Y10T 29/4943 20150115;
C25D 5/34 20130101; E03B 7/006 20130101; C23F 1/00 20130101; C23C
22/33 20130101; C23C 22/24 20130101; C25D 5/14 20130101 |
Class at
Publication: |
148/254 |
International
Class: |
C23C 022/78 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 1997 |
JP |
9-333361 |
Aug 20, 1998 |
JP |
10-234728 |
Claims
What is claimed is:
1. (Amended) A processing method of reducing elution of lead from a
lead-containing copper alloy, characterized by the step of
immersing the lead-containing copper alloy in an alkaline etching
solution to which an oxidant has been added to remove lead on the
surface thereof.
2. (Amended) A processing method of reducing elution of lead from a
lead-containing copper alloy according to claim 1, wherein either
one of an oxidant or a chelating agent, or both, are added to the
alkaline etching solution.
3. (Amended) A processing method of reducing elution of lead from a
lead-containing copper alloy, characterized by the step of
immersing the lead-containing copper alloy in chromic acid solution
to which fluoride has been added to remove lead on the surface
thereof.
4. (Deleted)
5. (Amended) A processing method of reducing elution of lead from a
lead-containing copper alloy, characterized by the step of
immersing the lead-containing copper alloy in a chromate solution
to which phosphoric acid has been added to form a chromate film on
the surface thereof.
6. (Deleted)
7. (Amended) A processing method of reducing elution of lead from a
lead-containing copper alloy, characterized by the step of
immersing the lead-containing copper alloy in an alkaline etching
solution to remove lead on the surface thereof, and subsequently
immersing the same in a chromic solution to which fluoride has been
added to remove lead on the surface thereof.
8. (Amended) A processing method of reducing elution of lead from a
lead-containing copper alloy, characterized by the step of
immersing the lead-containing copper alloy in an alkaline etching
solution to which an oxidant has been added to remove lead on the
surface thereof, and subsequently immersing the same in a chromate
solution to form a chromate film on the surface thereof.
9. (Amended) A processing method of reducing elution of lead from a
lead-containing copper alloy, characterized by the step of
immersing the lead-containing copper alloy in chromic acid to which
fluoride has been added to remove lead on the surface, and
subsequently immersing the same in a chromate solution to form a
chromate film on the surface thereof.
10. (Amended) A processing method of reducing elution of lead from
a lead-containing copper alloy, characterized by the step of
immersing the lead-containing copper alloy in an alkaline solution
to selectively remove lead on the surface thereof, and then
immersing the same in chromic acid solution to remove further lead
on the surface thereof, and subsequently immersing the same in a
chromate solution to which phosphoric acid has been added to form a
chromate film on the surface thereof.
11. (Deleted)
12. (Amended) A drinking water service fitting made of a
lead-containing copper alloy, characterized by the step of
immersing a lead-containing copper alloy material in an alkaline
etching solution to which an oxidant has been added to remove lead
on the surface thereof.
13. (Amended) A drinking water service fitting made of a
lead-containing copper alloy, characterized by the step of
immersing a lead-containing copper alloy material in a chromic acid
solution to which fluoride has been added to remove lead on the
surface thereof.
14. (Amended) A drinking water service fitting made of a
lead-containing copper alloy, characterized by the step of
immersing a lead-containing copper alloy material in a chromate
solution to which phosphoric acid has been added to form a chromate
film on the surface thereof.
15. (Amended) A drinking water service fitting made of a
lead-containing copper alloy, characterized by the step of
immersing a lead-containing copper alloy material in an alkaline
etching solution to which an oxidant has been added to remove lead
on the surface thereof, and subsequently immersing the same in a
chromate solution to form a chromate film on the surface
thereof.
16. (Amended) A drinking water service fitting made of a
lead-containing copper alloy, characterized by the step of
immersing a lead-containing copper alloy material in an alkaline
etching solution to remove lead on the surface thereof, and
subsequently immersing the same in a chromic acid solution to which
fluoride has been added to remove lead on the surface thereof.
17. (Amended) A drinking water service fitting made of a
lead-containing copper alloy, characterized by the step of
immersing a lead-containing copper alloy material in a chromic acid
solution to which fluoride has been added to remove lead on the
surface thereof, and subsequently immersing the same in a chromate
solution to form a chromate film on the surface thereof.
18. (Amended) A drinking water service fitting made of a
lead-containing copper alloy, characterized by the step of
immersing a lead-containing copper alloy material in an alkaline
solution to remove lead on the surface thereof, and then immersing
the same in a chromic acid solution to remove lead on the surface
thereof, and subsequently immersing the same in a chromate solution
to which phosphoric acid has been added to form a chromate film on
the surface thereof.
19. (Added) A plating method of reducing elution of lead from a
lead-containing copper alloy for plating the outer surface of the
lead-containing copper alloy and at the same time, removing lead on
the inner surface thereof.
20. (Added) A plating method of reducing elution of lead from a
lead-containing copper alloy according to claim 19, wherein
chromium plating is effected after nickel plating.
21. (Added) A plating method of reducing elution of lead from a
lead-containing copper alloy according to claims 19 and 20, wherein
an oxidant is contained in an alkaline degreasing solution for a
cleaning step before plating.
22. (Added) A plating method of reducing elution of lead from a
lead-containing copper alloy according to claim 20, wherein
fluoride is contained in a plating solution for chromium
plating.
23. (Added) A plating method of reducing elution of lead from a
lead-containing copper alloy according to claims 19 and 20, wherein
the lead-containing copper alloy is immersed in a chromate solution
after plating the outer surface thereof to form a chromate film on
the inner surface thereof.
24. (Added) A plating method of reducing elution of lead from a
lead-containing copper alloy according to claims 19 and 20, wherein
the lead-containing copper alloy is immersed in an alkaline
degreasing solution for a cleaning step before plating in which an
oxidant is contained, and plating is effected, after nickel
plating, in a chromium plating solution in which fluoride is
contained.
25. (Added) A drinking water service fitting made of a
lead-containing copper alloy, characterized by the step of plating
the outer surface of the lead-containing copper alloy and at the
same time, removing lead on the inner surface thereof.
26. (Added) A drinking water service fitting made of a
lead-containing copper alloy according to claim 25, wherein
chromium plating is effected after nickel plating.
27. (Added) A drinking water service fitting made of a
lead-containing copper alloy according to claims 25 and 26, wherein
an oxidant is contained in an alkaline degreasing solution for a
cleaning step before plating.
28. (Added) A drinking water service fitting made of a
lead-containing copper alloy according to claim 26, wherein
fluoride is contained in a plating solution for chromium
plating.
29. (Added) A drinking water service fitting made of a
lead-containing copper alloy according to claims 25 and 26, wherein
the lead-containing copper alloy is immersed in a chromate solution
after plating the outer surface thereof, to form a chromate film on
the inner surface thereof.
30. (Added) A drinking water service fitting made of a
lead-containing copper alloy according to claims 25 and 26, wherein
the lead-containing copper alloy is immersed in an alkaline
degreasing solution for a cleaning step before plating in which an
oxidant is contained, and chromium plating is effected, after
nickel plating, in a chromium plating solution in which fluoride is
contained.
31. (Added) A plating method of reducing elution of lead from a
lead-containing copper alloy according to claims 19 and 20, wherein
the lead-containing copper alloy is immersed in an alkaline
degreasing solution for a cleaning step before plating in which an
oxidant is contained, and plating is effected, after nickel
plating, in a chromium plating solution in which fluoride is
contained, and the lead-containing copper alloy is subsequently
immersed in a chromate solution to form a chromate film on the
inner surface thereof.
32. (Added) A drinking water service fitting made of a
lead-containing copper alloy according to claims 25 and 26, wherein
the lead-containing copper alloy is immersed in an alkaline
degreasing solution for a cleaning step before plating in which an
oxidant is contained, and plating is effected, after nickel
plating, in a chromium plating solution in which fluoride is
contained, and the lead-containing copper alloy is subsequently
immersed in a chromate solution to form a chromate film on the
inner surface thereof.
33. (Added) A plating method of reducing elution of lead according
to claims 19 and 20, wherein phosphoric acid is contained in a
chromate solution.
34. (Added) A plating method of reducing elution of lead according
to claims 25 and 26, wherein phosphoric acid is contained in a
chromate solution, and a drinking water service fitting made of a
lead-containing copper alloy available from the plating method.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a processing method for
reducing elution of lead from a lead-containing copper alloy, a
plating method for reducing elution of lead in a lead-containing
copper alloy, and a drinking water service fitting made of a
lead-containing copper alloy which exhibits reduced elution of
lead.
[0003] The drinking water service fittings include those which are
directly connected to a feed water pipe, such as water heater,
water cooler, ice-maker, water purifier, hot water boiler, vending
machine, pole tap, low tank, valve (faucet metals), joint, pipe,
sink, wash stand, stool, bath tub, housing unit, etc.
[0004] 2. Description of the Prior Art
[0005] Hitherto, faucet metals have been generally manufactured by
casting or forging a copper alloy such as bronze or brass, cutting
and polishing to shape, and then nickel chromium plating, etc.
[0006] To improve machinability of the copper alloy during cutting
in a manufacturing process, lead is added to the copper alloy.
[0007] FIG. 7 is a schematic view of composition of the copper
alloy to which lead is added. When lead is added to the copper
alloy 1, lead, lead oxide, lead hydroxide or the like gather near
the surface of the copper alloy, while lead 2 exists as a simple
substance in the inside thereof. The concentration of the lead 2
near the surface is several times higher than that of lead on the
inside.
[0008] In the faucet metals made of bronze casting to which lead is
added, lead of about 500 ppb elutes. Thus, lead elutes from the
surface of a water flow channel of the drinking water service
fittings made of a lead-containing copper alloy into water and as a
result, there is the possibility that drinking of such water for a
long time will exert a bad influence on a human body.
[0009] However, copper alloy materials to which lead is not added
has poor machinability, and a substitute copper alloy material has
not yet been developed.
SUMMARY OF THE INVENTION
[0010] It is, therefore, an object of the present invention to
provide a processing method for preventing elution of lead in a
lead-containing copper alloy by removing lead from the surface of a
lead-containing copper alloy material to prevent lead from eluting
from a faucet metal, etc. made of a lead-containing copper alloy, a
plating method for reducing elution of lead in a lead-containing
copper alloy, and a drinking water service fitting made of a
lead-containing copper alloy in which elution of lead has been
prevented.
[0011] The present invention pays attention to a property of lead
as an amphoteric metal, wherein a lead-containing copper alloy is
immersed in an alkaline etching solution to which an oxidant is
added, to selectively dissolve and remove lead on the surface of a
lead-containing copper alloy material.
[0012] Thus, both a chemical reaction whereby lead on the surface
of a lead-containing copper alloy material contacts an alkaline
solution so as to directly become an alkali metal salt of a
water-soluble zincate, and a chemical reaction whereby the lead is
first converted to lead oxide by an oxidant and this lead oxide is
converted to an alkali metal salt of a water-soluble zincate by an
alkaline solution, proceed together. However, the chemical reaction
of the latter advances faster than that of the former and as a
result, dissolution of lead is expedited to remove lead.
[0013] When this chemical reaction occurs, copper (a simple
substance), tin forming an alloy together with copper, zinc,
aluminum, etc. do not react to the alkaline solution, and only the
lead (a simple substance ) which does not form an alloy together
with copper is selectively removed by the above-mentioned chemical
reaction.
[0014] It is desirable to further add a chelating agent to this
etching solution. By adding the chelating agent, lead is formed
with a water-soluble complex and it is possible to effectively
remove lead.
[0015] Further, it is desirable to form a chromate film on the
surface of a lead-containing copper alloy material after lead on
the surface of the lead-containing copper alloy material is
dissolved and removed.
[0016] Namely, a chemical reaction that dissolves a lead-containing
copper alloy, and a chemical reaction that forms a chromate film
are caused by chromic acid contained in a chromate solution so as
to dissolve and remove the lead left in a limited amount on the
surface of a lead-containing copper alloy material. Also, the
surface of the lead-containing copper alloy material from which
lead has been removed is protected by a chromate film. Lead on the
inside does not elute even though the surface of the
lead-containing copper alloy material from which lead has been
removed corrodes due to long term water flow. It is therefore
possible to reduce elution of lead for a long period.
[0017] Further, the present invention pays attention to the point
that in a plating step such as nickel chromium plating to be
effected on a lead-containing copper alloy, this alloy is usually
immersed in a plating solution. The outer surface of the
lead-containing copper alloy is therefore plated and, at the same
time, lead on the inner surface is dissolved and removed.
[0018] An alkaline degreasing solution is used as a pre-cleaning
step for plating, but an oxidant is contained in the solution to
expedite dissolution and removal of lead on the inner surface of a
lead-containing copper alloy material. Also, addition of fluoride
to a chromium plating solution serves to effectively dissolve
deposits of lead chromate.
[0019] Further, a lead-containing copper alloy material may be
immersed in a chromate solution to form a chromate film on the
inner surface thereof after plating the outer surface thereof. With
this film formation, it is possible to reduce elution of lead left
in a limited amount on the surface of the lead-containing copper
alloy material. It is desirable to add a phosphoric acid to the
chromate solution.
[0020] The lead-containing copper alloy material is degreased in an
alkaline degreasing solution as a cleaning step before plating in a
solution in which an oxidant is contained. Acid activation and
nickel plating are subsequently effected and then, chromium plating
is effected in a chromium plating solution that contains fluoride.
Thus, it is possible to dissolve and remove lead on the inner
surface of the lead-containing copper alloy material while
effecting nickel chromium plating on the outer surface thereof.
[0021] Further, the lead-containing copper alloy material is
degreased in an alkaline degreasing solution as a cleaning step
before plating in a solution which contains an oxidant. Acid
activation and nickel plating are subsequently effected and then,
chromium plating is effected in a sargent chromium plating bath or
a chromium fluoride plating bath. The lead-containing copper alloy
material is further immersed in a chromate solution to form a
chromate film on the inner surface thereof. It is possible to
dissolve and remove lead on the inner surface of the
lead-containing copper alloy material while effecting nickel
chromium plating on the outer surface thereof. It is desirable to
include a phosphoric acid in the chromate solution.
[0022] The faucet metals mainly use a lead-containing copper alloy
material such as bronze or brass, and various plating steps are
effected to improve the beauty of the outer surface, corrosion
resistance, and wear and abrasion resistance. According to the
present invention, plating is effected on the outer surface of the
lead-containing copper alloy material while reducing elution of
lead on the inner surface thereof at the same time. It is therefore
possible to reduce elution of lead in various plating steps
including nickel chromium plating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a view showing an elution effect on lead when lead
elutes by alkaline etching;
[0024] FIG. 2 is a view showing an analytical result of the
concentration of lead elution when chromium plating bath treatment
is effected after alkaline etching;
[0025] FIG. 3 is a view showing an analytical result of the
concentration of lead elution when a chromate process is effected
after alkaline etching;
[0026] FIG. 4 is a schematic view showing the condition where lead
has been eluted by alkaline etching;
[0027] FIG. 5 is a schematic view showing the condition of a
plating bath treatment in a chromium fluoride bath;
[0028] FIG. 6 is a schematic view showing the condition of a
chromate treatment; and
[0029] FIG. 7 is a schematic view showing the composition of a
copper alloy to which lead has been added.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] The present invention pays attention to the property of lead
as an amphoteric metal, wherein a lead-containing copper alloy is
immersed in an alkaline etching solution to which an oxidant has
been added to selectively dissolve and remove lead on the surface
of a lead-containing copper alloy material. Also, the
lead-containing copper alloy is immersed in a chromic acid solution
to dissolve lead on the surface thereof. It is also possible to
dissolve and remove lead on the surface of the lead-containing
copper alloy material by immersing the lead-containing copper alloy
in the alkaline etching solution, and then immersing the same in a
chromic acid solution. When any one or a plurality of an oxidant,
chelating agent and surface active agent are added to the alkaline
etching solution, and when fluoride is added to a chromic acid
solution, it is possible to effectively remove lead.
[0031] A chromate film may also be formed on the surface of a
lead-containing copper alloy material. With this film formation, it
is possible to reduce elution of the lead left in a limited amount
on the surface. A drinking water service fitting made of a
lead-containing copper alloy is immersed in an alkaline etching
solution in a pre-processing step for a nickel chromium plating
step to selectively remove lead on the surface of the
lead-containing copper alloy material and is then activated in a
solution such as sulfuric acid and hydrochloric acid. Nickel
plating is subsequently effected, and then chromium plating is
effected in a Sargent chromium or chromium fluoride bath, and a
chromate film may be formed by immersing the drinking water service
fitting in a chromate solution.
[0032] When chromium plating is effected in a chromium fluoride
plating bath where fluoride has been substituted for a part or all
of sulfuric acid in a sargent bath consisting of ordinary sargent
chromium or chromic acid anhydride and sulfuric acid, a chromic
acid solution will not only dissolve the entire copper alloy
material, but also dissolve lead because the chromic acid solution
contained in a chrome plating bath is a strong acid.
[0033] Thus, it is possible to effect nickel chromium plating on
the outer surface of the drinking water service fitting and at the
same time, to remove lead on the surface of a water flow channel of
the inner surface thereof.
[0034] A plating process usually consists of a degreasing step and
a plating step. The degreasing step is a step for removing stains
such as a grease component attached to a material to secure
adhesion of plating. A main component of the alkaline etching
solution which is used in the present invention is an alkaline
solution that has dissolved any one or several kinds of sodium
hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate,
sodium tripolyphosphate, sodium metasilicate, sodium orthosilic
acid, etc. The concentration is general between several grams/l and
several tens of grams/l and it can be selectively decided depending
on the combination of the components used therein.
[0035] A temperature of about 60- 90.degree. C. is desirable
because the higher the temperature, the higher the effect of lead
elution. Immersion time of between several minutes and several tens
of minutes is desirable. As shown in FIG. 4, a copper metal does
not generally infiltrate, but it is possible to selectively
dissolve lead as an amphoteric metal. The plating process usually
consists of a degreasing step and a plating step. The degreasing
step is a step for removing stains such as a grease component
attached to a material to secure the adhesion of plating. An
alkaline etching solution used in the present invention acts as an
alkaline degreasing solution.
[0036] To improve penetration and wettability of an alkaline
etching solution, a surface-active agent is added for the purpose
of reducing surface tension of the solution. An anionic
surface-active agent or a nonionic surface-active agent is mainly
used as the surface-active agent and these can be used alone or
together. The anionic surface-active agent includes higher fatty
acid sodium, sulfonated oil, higher alcohol sodium sulphate,
alkylbenzene sodium sodium sulphate, higher alkyl ether sodium
sulphate, and alpha olefin sodium sulphate.
[0037] Also, the nonionic surface-active agent includes alkyl
polyoxyethylene ether, alkyl phenyl polyoxyethylene ether, fatty
acid ethylene oxide adduct, polypropylene glycol ethylene oxide
adduct (Pluronic). An amount of addition between several grams/l
and several tens of grams/l is general.
[0038] It is also possible to add a chelating agent to prevent
reattaching of lead as hydroxide and to expedite dissolution of
lead. Desirable as the chelating agent, for example, is an chemical
compound which can easily form a complex together with lead of
EDTA, ethylene diamine, triethanolamine, thiourea, Rochelle salt
and tartaric acid, etc. A concentration between several grams/l and
several tens of grams/l is desirable for each component.
[0039] When an oxidant is added in an alkaline etching solution,
lead is oxidized and dissolves in alkali through lead oxide (PbO,
etc. [reaction formula (2) of FIG. 4]. This reaction (2) is
effected faster than the reaction (1) and as a result, expedites
dissolving lead. Used as the oxidant, for example, are an organic
oxidizing compound such as meta-nitrobenzene sodium sulfonate,
P-nitro sodium bonzoate, and an inorganic compound such as
hypochlorite, bleaching powder, hydrogen peroxide, potassium
permanganate, persulfate, and perchlorate. A concentration between
several grams/l and several tens of grams/l is desirable for each
component.
[0040] A chromium fluoride bath is available as a bath used for
chromic acid immersion. This chromic fluoride bath can use a
generally well-known sargent chromium plating bath, but the
fluoride is substituted for a part or all of sulfuric acid in a
sargent bath consisting of chromic acid anhydride and sulfuric
acid.
[0041] When chromium plating is effected in a chromium plating
solution, chromium plating is effected on the outer surface of a
copper alloy material, but the entire part of the inner surface
dissolves while lead dissolves because the chromium plating
solution has strong acidic properties. However, there is the
possibility that deposits remain as lead chromate when fluoride
does not exist [reaction formula (3) in FIG. 5]. Since fluoride
serves to dissolve such deposits, it is desirable to effect
chromium plating in the chromium fluoride bath [reaction formula
(4) in FIG. 5]. A temperature between 40.degree. C. and 60.degree.
C. and immersion time between several tens of seconds and several
minutes are desirable respectively.
[0042] Used as fluoride are almost all the fluorine compounds such
as sodium fluoride, potassium fluoride, ammonium fluoride,
hydrofluoric acid, boro-hydrofluoric acid, hydrofluosilic acid,
sodium silicofluoride, potassium silicofluoride, and boro-chromium
fluoride.
[0043] An additive agent used in a chromate processing is based on
chromic acid anhydride, phosphoric acid and sulfuric acid, but
nitric acid, hydrofluoric acid, acetic acid, oxalic acid, chromate,
etc. are added or substituted as the case may be. A chromate agent
such as a galvanizing agent on the market may be used.
[0044] A concentration between several grams/l and several tens of
grams/l is desirable for each component. A processing temperature
between room temperature and 60.degree. C., and a processing time
between several seconds and several minutes are desirable
respectively. By immersing a completed product with its outer
surface plated in this chromate solution, a chromate film can be
formed on the inner surface by a reaction formula, as shown in FIG.
6, to control elution of lead. By adding phosphoric acid to chromic
acid anhydride which is the main component of the chromate
solution, it is possible to improve the control effect of lead
elution with a synergistic effect.
[0045] (1) Alkaline Etching Solution
[0046] A lead elution effect of the alkaline etching solution and a
lead elution effect when an oxidant and a chelating agent are added
to the alkaline etching solution are shown in FIG. 1.
[0047] Processing is effected in the following steps. Faucet metals
made of bronze casting are immersed in various etching solutions as
shown in FIG. 1 for 3 minutes at 80.degree. C., and then washed for
30 seconds. They are subsequently immersed in a chromium fluoride
plating solution on the market with a fluorine contents of about 1
gram/l, for 3 minutes at 45.degree. C. and then washed for 30
seconds. These metals are subsequently washed with hot water for 30
seconds at 60.degree. C.
[0048] Processed faucet metals were then analyzed to see the
concentration of lead eluted in accordance with "Drinking water
service fittings--Percolation performance test method" by JIS S
3200-7 (1997). FIG. 4 is a schematic view showing the condition
where lead is eluted by the alkaline etching, wherein lead 2 on the
surface of a lead-containing copper alloy 1 is selectively removed
by a reaction formula as shown in FIG. 4.
[0049] As can be seen from the results in FIG. 2, an untreated
sample without etching has a lead elution amount of 500 ppb, while
the lead elution amount for the products treated according to the
present invention is remarkably reduced. In particular, the lead
elution amount of the treated products was further reduced by
addition of the oxidant and the chelating agent. It is to be noted
that immersion of the products in the chromium fluoride plating
solution enables the lead elution amount to be reduced further.
[0050] (2) Chromium Plating Solution
[0051] Next, faucet metals made of bronze casting are immersed in
an alkaline etching solution (sodium hydroxide 50 g/l,
meta-nitrobenzene sodium sulfonate 2 g/l, EDTA 2 g/l, ethylene
diamine 2 g/l) for 3 minutes at 80.degree. C. and then washed for
30 seconds. The faucet metals are subsequently immersed in a
chromium plating solution as shown in FIG. 2 for 3 minutes at
45.degree. C., washed for 30 seconds, and then washed with hot
water for 30 seconds at 60.degree. C. The faucet metals were then
analyzed to obtain the concentration of lead elution in accordance
with JIS S 3200-7 (1997). The result of this analysis is shown in
FIG. 2.
[0052] As seen from FIG. 2, the lead elution amount is remarkably
reduced when immersed in the chromium plating solution, but the
chromium fluoride bath is more effective than the conventional
sargent chromium bath. The sargent bath where fluoride does not
exist is considered to have had a slightly higher concentration of
lead because deposits remain as lead chromate [reaction formula (3)
of FIG. 5]. The fluoride, which dissolves the deposits, is
considered to have had a better effect in the chromium fluoride
bath than the sargent chromium bath [reaction formula (4) of FIG.
5]. It is also obvious that even immersion in chromic acid only has
a lead elution effect.
[0053] (3) Chromate Processing
[0054] Faucet metals made of bronze casting are immersed in an
alkaline etching solution (sodium hydroxide 50 g/l,
meta-nitrobenzene sodium sulfonate 2 g/l, EDTA 2 g/l, ethylene
diamine 2 g/l) for 3 minutes at 80.degree. C. and then washed for
30 seconds. The faucet metals are subsequently immersed in a
chromium fluoride plating solution (the above-mentioned bath on the
market with a fluorine content of about 1 g/l) for 3 minutes at
45.degree. C. and then, washed for 30 seconds. Next, chromate
treatment is effected in a chromate solution with a composition as
shown in FIG. 3 for 20 seconds at 30.degree. C., washed for 30
seconds, and washed with hot water for 30 seconds at 60.degree.
C.
[0055] The faucet metals are then analyzed to obtain the elution
concentration of lead in accordance with JIS S 3200-7 (1997). The
analytic results are shown in FIG. 3.
[0056] As shown in FIG. 3, as compared with the case without
chromate treatment, the lead elution amount of the product effected
with chromate treatment is reduced, and the lead elution can be
remarkably controlled, especially with the synergistic effect of
chromic acid anhydride with phosphoric acid. Namely, with the
synergistic effect of chromic acid and phosphoric acid contained in
the chromate solution, a chemical reaction for dissolving a
lead-containing copper alloy and a chemical reaction for forming
chromate film are caused to remove the lead left in a limited
amount on the surface of a lead-containing copper alloy material.
By removing the lead, the chromate film is provided to protect the
surface of the lead-containing copper alloy material. It is
therefore possible to reduce elution of lead for a long time
because the lead situated inside the lead-containing copper alloy
material is not eluted even when the surface thereof corrodes due
to water flow for a long time. With this chromate treatment, the
chromate film is formed by a reaction formula in the schematic view
showing the condition of chromate treatment in FIG. 6 to control
elution of lead. It is obvious that even the chromate treatment
only has a good effect on the elution of lead.
[0057] According to the present invention, by immersing drinking
water service fittings made of lead-containing copper alloy in an
alkaline etching solution to which an oxidant is added to remove
lead on the surface thereof, it is possible to effectively reduce
elution of lead used in the drinking water service fittings. If a
chelating agent is added to this etching solution, it is possible
to further improve prevention of lead elution.
[0058] The drinking water service fittings made of a
lead-containing copper alloy are immersed in an alkaline solution
to which an oxidant is added to remove lead on the surface thereof.
They are subsequently immersed in a chromate solution to form a
chromate film on the surface thereof. With this film formation, it
is possible to remarkably reduce elution of lead.
[0059] By immersing the drinking water service fittings made of a
lead-containing copper alloy in a chromic acid solution to which
fluoride has been added to remove lead on the surface thereof, it
is possible to effectively reduce elution of lead used in the
drinking water service fittings.
[0060] After the drinking water service fittings made of a
lead-containing copper alloy are immersed in an alkaline etching
solution to remove lead on the surface thereof, they are further
immersed in a chromic acid solution to which fluoride has been
added. With this immersion, it is possible to remarkably reduce
elution of lead.
[0061] If an oxidant and a chelating agent are added to the etching
solution, it is possible to further improve prevention of lead
elution.
[0062] Since the drinking water service fittings made of a
lead-containing copper alloy are immersed in a chromate solution to
which phosphoric acid is added to form a chromate film thereon, It
is possible to effectively reduce elution of lead used in the
drinking water service fittings.
[0063] The drinking water service fittings made of a
lead-containing copper alloy are immersed in an alkaline etching
solution and then immersed in a chromic acid solution to remove
lead on the surface thereof. Since they are subsequently immersed
in a chromate solution to which phosphoric acid has been added to
form a chromate film on the surface, it is possible to remarkably
reduce elution of lead.
[0064] The drinking water service fittings made of a
lead-containing copper alloy are immersed in a chromic acid
solution to which fluoride has been added to remove lead on the
surface thereof. Since they are subsequently immersed in a chromate
solution to form a chromate film on the surface thereof, it is
possible to reduce elution of lead from the inside thereof and to
remarkably reduce elution of lead.
[0065] Further, when the alkaline etching solution is used as a
pre-processing agent for plating, it is possible to improve
degreasing strength of stains and oil on the surface of a material
and at the same time, to improve the outer appearance and adhesion
of plating.
[0066] Still further, the drinking water service fittings made of a
lead-containing copper alloy are immersed in an alkaline solution
to remove lead on the surface thereof, and then immersed in a
chromic acid solution to further remove lead on the surface
thereof. Since they are subsequently immersed in a chromate
solution to form a chromate film, it is possible to remarkably
reduce elution of lead.
* * * * *