U.S. patent application number 10/279842 was filed with the patent office on 2003-05-29 for heat exchanger, fluorination method of heat exchanger or its components and manufacturing method of heat exchanger.
This patent application is currently assigned to SHOWA DENKO K.K.. Invention is credited to Nakagawa, Shintaro, Nakata, Yoshinori, Ohashi, Tadao, Ohira, Yoshitaka, Tada, Kiyoshi, Usui, Tadashi, Wakabayashi, Nobuhiro.
Application Number | 20030098145 10/279842 |
Document ID | / |
Family ID | 26624115 |
Filed Date | 2003-05-29 |
United States Patent
Application |
20030098145 |
Kind Code |
A1 |
Tada, Kiyoshi ; et
al. |
May 29, 2003 |
Heat exchanger, fluorination method of heat exchanger or its
components and manufacturing method of heat exchanger
Abstract
The heat exchanger according to the present invention includes a
heat exchanger component in which a fluoride layer 10 is formed at
the surface layer portion. It is preferable that the fluoride layer
10 falls within the range of from 2 nm to 10 .mu.m in thickness. It
is preferable that the component is at least one of a fin and a
plate. Furthermore, it is preferable that the fluoride layer 10 is
formed on a substrate via an intermediate layer 2. It is preferable
that the intermediate layer 2 includes an anodized oxide layer 3
and/or a nickel plated layer 4. The heat exchanger is excellent in
corrosion resistance against water, vapor and the like The heat
exchanger is preferably used, especially, for a fuel cell.
Inventors: |
Tada, Kiyoshi; (Oyama-shi,
JP) ; Ohira, Yoshitaka; (Oyama-shi, JP) ;
Usui, Tadashi; (Oyama-shi, JP) ; Nakata,
Yoshinori; (Oyama-shi, JP) ; Nakagawa, Shintaro;
(Oyama-shi, JP) ; Wakabayashi, Nobuhiro;
(Oyama-shi, JP) ; Ohashi, Tadao; (Tochigi-shi,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
SHOWA DENKO K.K.
Minato-ku
JP
|
Family ID: |
26624115 |
Appl. No.: |
10/279842 |
Filed: |
October 25, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60341249 |
Dec 20, 2001 |
|
|
|
Current U.S.
Class: |
165/166 ;
165/133 |
Current CPC
Class: |
Y02E 60/50 20130101;
Y02P 70/50 20151101; F28F 19/04 20130101; H01M 8/04067
20130101 |
Class at
Publication: |
165/166 ;
165/133 |
International
Class: |
F28F 013/18; F28F
019/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 25, 2001 |
JP |
2001-328184 |
Claims
What is claimed is:
1. A heat exchanger including a heat exchanger component having a
surface layer portion in which a fluoride layer is formed.
2. The heat exchanger as recited in claim 1, wherein a thickness of
said fluoride layer falls within the range of from 2 nm to 10
.mu.m.
3. The heat exchanger as recited in claim 1, wherein said heat
exchanger is a fin-plate type heat exchanger, and wherein said
component is at least one of a fin and a plate.
4. The heat exchanger as recited in claim 1, wherein said heat
exchanger uses water as heat medium.
5. The heat exchanger as recited in claim 1, wherein said beat
exchanger is used under a water environment, a vapor environment,
or a fuel gas environment of a fuel cell.
6. The heat exchanger as recited in claim 1, wherein a layer
containing catalyst is formed on a surface of said fluoride
layer.
7. The heat exchanger as recited in claim 1, wherein said heat
exchanger is for use in a fuel cell.
8. The heat exchanger as recited in claim 1, wherein said heat
exchanger is a fin-plate type heat exchanger for a fuel tell to be
used under a fuel gas environment of a fuel cell, and wherein a
layer containing catalyst for accelerating a reaction of carbon
monoxide contained in the fuel gas and oxygen.
9. The heat exchanger as recited in claim 1, wherein a substrate of
said component is substantially made of aluminum or its alloy.
10. The heat exchanger as recited in claim 1, wherein said fluoride
layer is formed on a surface of a substrate of said component.
11. The heat exchanger as recited in claim 10, wherein said
fluoride layer is substantially made of fluoride generated by
performing fluorination processing of said surface of said
substrate.
12. The heat exchanger as recited in claim 1, wherein said fluoride
layer is formed on a surface of an intermediate layer formed on a
surface of a substrate of said component.
13. The heat exchanger as recited in claim 12, wherein said
fluoride layer is substantially made of fluoride generated by
performing fluorination processing of said surface of said
intermediate layer.
14. The heat exchanger as recited in claim 12 or 13, wherein said
intermediate layer includes a layer which is substantially made of
oxide generated by performing forcible oxidation of said surface of
said substrate.
15. The heat exchanger as recited in claim 12 or 13, wherein said
intermediate layer includes an anodized oxide layer formed by
anodizing said surface of said substrate.
16. The heat exchanger as recited in claim 1, wherein said fluoride
layer is formed on a surface of an anodized oxide layer formed by
anodizing a surface of a substrate of said component and
substantially made of fluoride generated by performing fluorination
processing of said surface of said anodized oxide layer.
17. The heat exchanger as recited in claim 1, wherein said fluoride
layer is formed on a surface of a plated layer containing nickel
formed on a surface of a substrate of said component and
substantially made of fluoride generated by performing fluorination
processing of said surface of said plated layer.
18. The heat exchanger as recited in claim 17, wherein said plated
layer is substantially made of electroless nickel plating.
19. The heat exchanger as recited in claim 17, wherein said plated
layer is substantially made of electroless nickel-phosphorus alloy
plated layer.
20. The heat exchanger as recited in claim 1, wherein said fluoride
layer is formed on a surface of a plated layer constituting an
intermediate layer including an anodized oxide layer formed by
anodizing a surface of a substrate of said component and said
plated layer formed on a surface of said anodized oxide layer and
containing nickel, and substantially made of fluoride generated by
performing fluorination processing of said surface of said plated
layer.
21. The heat exchanger as recited in claim 20, wherein said plated
layer is substantially made of electroless nickel plating.
22. The heal exchanger as recited in claim 20, wherein said plated
layer is substantially made of electroless nickel-phosphorus alloy
plating.
23. A method of fluorinating a heat exchanger or its component,
comprising: heating a heat exchanger or its component in an
atmosphere containing a fluorination processing gas to thereby form
a fluoride layer in a surface layer portion of said heat exchanger
or its component.
24. The method of fluorinating a heat exchanger or its component as
recited in claim 23, wherein said fluorination processing gas is at
least one gas selected from the group consisting of a fluorine gas,
a chlorine trifluoride gas and a nitrogen fluoride gas, wherein an
inert gas is used as a base gas of said atmosphere, and wherein
concentration of said fluorine gas or that of said fluoride gas is
set so as to fall within the range of from 5 to 80 mass %.
25. The method of fluorinating a heat exchanger or its component as
recited in claim 24, wherein said concentration of said fluorine
gas or that of said fluoride gas is set so as to fall within the
range of from 10 to 60 mass %.
26. The method of fluorinating a heat exchanger or its component as
recited in claim 23, wherein said heating is performed under a heat
processing condition that a holding temperature is 100.degree. C.
or more and a holding time is 5 hours or more.
27. A method of fluorinating a heat exchanger or its component,
comprising: implanting an ionized fluorine into at least a part of
a surface of a heat exchanger or its component to thereby form a
fluoride layer on a surface layer portion of said heat exchanger or
its component.
28. A method of manufacturing a heat exchanger, comprising: a
heating step for heating a heat exchanger component in an
atmosphere containing a fluorination processing gas; and a fixing
step for fixing said component processed by said heating step to a
predetermined position of a desired heat exchanger.
29. The method of manufacturing a heat exchanger as recited in
claim 28, further comprising a catalyst containing layer forming
step for forming a layer containing catalyst on a surface of said
component processed by said heating step.
30. A method of manufacturing a heat exchanger, comprising: a
fluorine implanting step for implanting an ionized fluorine into at
least a part of a surface of a heat exchanger component; and a
fixing step for fixing said component processed by said fluorine
implanting step to a predetermined position of a desired heat
exchanger.
31. The method of manufacturing a heat exchanger according to claim
30, further comprising a catalyst containing layer forming step for
forming a layer containing catalyst on a portion of said surface of
said component processed by said fluorine implanting stop to which
said fluorine is implanted.
32. A method of manufacturing a heat exchanger, comprising: a
heating step for heating a heat exchanger assembly in an atmosphere
containing a fluorination processing gas, wherein said heat
exchanger assembly is formed by assembling a plurality of heat
exchanger components and integrally brazing said plurality of heat
exchanger components in an assembled state.
33. The method of manufacturing a heat exchanger as recited in
claim 32, further comprising a catalyst containing layer forming
step for forming a layer containing catalyst on a surface of said
assembly processed by said heating step.
34. A method of manufacturing a heat exchanger, comprising: a
fluorine implanting step for implanting an ionized fluorine into at
least a part of a surface of a heat exchanger assembly, wherein
said heat exchanger assembly is formed by assembling a plurality of
heat exchanger components and integrally brazing said plurality of
heat exchanger components in an assembled state.
35. The method of manufacturing a heat exchanger as recited in
claim 34, further comprising a catalyst containing layer forming
step for forming a layer containing catalyst on a portion of said
surface of said assembly processed by said fluorine implanting step
to which said fluorine is implanted.
Description
[0001] Priority is claimed to Japanese Patent Application No.
2001-328184, filed on Oct. 25, 2001 and U.S. Provisional Patent
Application No. 60/341,249, filed on Dec. 20, 2001, the disclosure
of which are incorporated by reference in their entireties.
CROSS REFERENCE TO RELATED APPLICATIONS
[0002] This application is an application filed under 35 U.S.C.
.sctn.111 (a) claiming the benefit pursuant to 35 U.S.C.
.sctn.119(e) (1) of the filing date of U.S. Provisional Application
No. 60/341, 249 filed on Dec. 20, 2001 pursuant to 35 U.S.C.
.sctn.111(b).
FIELD OF THE INVENTION
[0003] The present invention relates to a heat exchanger to be used
as, for example, an evaporator, a condenser, a radiator or an oil
cooler, a method of fluorinating a heat exchanger or its components
and a method of manufacturing a heat exchanger. More specifically,
the present invention relates to a heat exchanger preferably used
as a heat exchanger using water (especially, hot water of room
temperature to 100.degree. C. or hot water containing long-life
coolant of 80 to 150.degree. C.) as heat medium, a heat exchanger
preferably used especially for a heat exchanger under a water
environment, a vapor environment, a fuel cell gas environment or
the like, a method of fluorinating a heat exchanger or its
components and a method of manufacturing a heat exchanger.
BACKGROUND ART
[0004] Metallic materials have been used as materials of heat
exchangers for automobiles, etc. from a long time ago because it
generally has characteristics such as an easy-to-work
characteristic and high thermal conductivity. Due to its
insufficient corrosion resistance, however, various cases in which
heat exchangers lost their function due to the corrosion from the
surface thereof that caused penetration in sort time were
reported.
[0005] As the countermeasures thereof, various anti-corrosion
processings are conventionally conducted to a heat exchanger or the
surfaces of the components. For example, a formation of chemical
conversion coating on a surface of a heat exchanger or its
components was performed as corrosion resistance processing.
[0006] Furthermore, recently, in order to improve the corrosion
resistance, various improvements are made to the aforementioned
corrosion resistance processing. For example, according to Japanese
Patent No. 2,076,381 (Japanese Examined Laid-open Patent
Publication No. H7-109355 and U.S. Pat. No. 4,726,886), in a
fin-tube type heat exchanger, after conducting chemical conversion
treatment on the surfaces of the fins and the tubes, the treated
fins and tubes are immersed in a mixed water solution of polyvinyl
pyrrolidone and potassium silicate, thereby improving the corrosion
resistance (see Patent Document No. 1).
[0007] Patent Document No. 1
[0008] Japanese Examined Laid-open Patent Application No.
7-109355
[0009] (see pages 2-5, FIG. 6)
[0010] (U.S. Pat. No. 4,726,886)
[0011] However, according to the aforementioned corrosion
resistance processing method, a metallic oxide layer is formed on a
surface of a beat exchanger or its components. However, since the
metallic oxide layer is poor against water, especially hot water of
a room temperature to 100.degree. C., the conventional corrosion
resistance processing method was poor in reliability against
water.
[0012] Especially, in recent years, in a heat exchanger for a fuel
cell, it has been desired that a corrosion resistance processing
method excellent in reliability against water, vapor and a fuel gas
of a fuel cell is developed.
[0013] The present invention was made in view of the aforementioned
technical background, and aims to provide a heat exchanger
excellent in corrosion resistance, a method of fluorinating a heat
exchanger or its components and a method of manufacturing a heat
exchanger.
[0014] Another object of the present invention will be apparent
from the following detailed embodiments of the present
invention.
DISCLOSURE OF THE INVENTION
[0015] The present invention provides the following means:
[0016] (1) A heat exchanger including a heat exchanger component
having a surface layer portion in which a fluoride layer is
formed.
[0017] (2) The heat exchanger as recited iii the aforementioned
item (1), wherein a thickness of the fluoride layer falls within
the range of from 2 nm to 10 .mu.m.
[0018] (3) The heat exchanger as recited in the aforementioned item
(1), wherein the heat exchanger is a fin-plate type heat exchanger,
and wherein the component is at least one of a fin and a plate.
[0019] (4) The heat exchanger as recited in the aforementioned item
(1), wherein the heat exchanger uses water as beat medium.
[0020] (5) The heat exchanger as recited in the aforementioned item
(1), wherein the heat exchanger is used under a water environment,
a vapor environment, or a fuel gas environment of a fuel cell.
[0021] (6) The heat exchanger as recited in the aforementioned item
(1), wherein a layer containing catalyst is formed on a surface of
the fluoride layer.
[0022] (7) The heat exchanger as recited in the aforementioned item
(1), wherein the heat exchanger is for use in a fuel cell.
[0023] (8) The heat exchanger as recited in the aforementioned item
(1), wherein the heat exchanger is a fin-plate type heat exchanger
for a fuel cell to be used under a fuel gas environment of a fuel
cell, and wherein a layer containing catalyst for accelerating a
reaction of carbon monoxide included in the fuel gas and
oxygen.
[0024] (9) The heat exchanger as recited in the aforementioned item
(1), wherein a substrate of the component is substantially made of
aluminum or its alloy.
[0025] (10) The heat exchanger as recited in the aforementioned
item (1), wherein the fluoride layer is formed on a surface of the
substrate of the component.
[0026] (11) The heat exchanger as recited in the aforementioned
item (10), wherein the fluoride layer is substantially made of
fluoride generated by performing fluorination processing of the
surface of the substrate.
[0027] (12) The heat exchanger as recited in the aforementioned
item (1), wherein the fluoride layer is formed on a surface of an
intermediate layer formed on a surface of the substrate of the
component.
[0028] (13) The heat exchanger as recited in the aforementioned
item (12), wherein the fluoride layer is substantially made of
fluoride generated by performing fluorination processing of the
surface of the intermediate layer.
[0029] (14) The heat exchanger as recited in the aforementioned
item (12) or (13), wherein the intermediate layer includes a layer
which is substantially made of oxide generated by performing
forcible oxidation of the surface of the substrate.
[0030] (15) The heat exchanger as recited in aforementioned item
(12) or (13), wherein the intermediate layer includes an anodized
oxide layer formed by anodizing the surface of the substrate.
[0031] (16) The heat exchanger as recited in the aforementioned
item (1), wherein the fluoride layer is formed on a surface of an
anodized oxide layer formed by anodizing a surface of a substrate
of the component and substantially made of fluoride generated by
performing fluorination processing of the surface of the anodized
oxide layer.
[0032] (17) The heat exchanger as recited in the aforementioned
item (1), wherein the fluoride layer is formed on a surface of a
plated layer containing nickel formed on a surface of a substrate
of the component and substantially made of fluoride generated by
performing fluorination processing of the surface of the plated
layer.
[0033] (18) The heat exchanger as recited in the aforementioned
item (17), wherein the plated layer is substantially made of an
electroless nickel plating.
[0034] (19) The heat exchanger as recited in the aforementioned
item (17), wherein the plated layer is substantially made of
electroless nickel-phosphorus alloy plating.
[0035] (20) The heat exchanger as recited in the aforementioned
item (1), wherein the fluoride layer is formed on a surface of the
plated layer constituting an intermediate layer including an
anodized oxide layer formed by anodizing the surface of the
substrate of the component and the plated layer formed on a surface
of the anodized oxide layer and containing nickel, and
substantially made of fluoride generated by performing fluorination
processing of the surface of the plated layer.
[0036] (21) The heat exchanger as recited in the aforementioned
item (20), wherein the plated layer is substantially made of
electroless nickel plating.
[0037] (22) The heat exchanger as recited in the aforementioned
item (20), wherein the plated layer is substantially made of
electroless nickel-phosphorus alloy plating.
[0038] (23) A method of fluorinating a heat exchanger or its
component, comprising;
[0039] heating a heat exchanger or its component in an atmosphere
containing a fluorination processing gas to thereby form a fluoride
layer in a surface layer portion of the heat exchanger or its
component.
[0040] (24) The method of fluorinating a heat exchanger or its
component as recited in the aforementioned item (23), wherein the
fluorination processing gas is at least one gas selected from the
group consisting of a fluorine gas, a chlorine trifluoride gas and
a nitrogen fluoride gas, wherein an inert gas is used as a base gas
of the atmosphere, and wherein concentration of the fluorine gas or
that of the fluoride gas is set so as to fall within the range of
from 5 to 80 mass %.
[0041] (25) The method of fluorinating a heat exchanger or its
component as recited in the aforementioned item (24), wherein the
concentration of the fluorine gas or that of the fluoride gas is
set so as to fall within the range of from 10 to 60 mass %.
[0042] (26) The method of fluorinating a heat exchanger or its
component as recited in the aforementioned item (23), wherein the
heating is performed under heat processing conditions that a
holding temperature is 100.degree. C. or more and a holding time is
5 hours or more.
[0043] (27) A method of fluorinating a heat exchanger or its
component, comprising:
[0044] implanting an ionized fluorine into at least a part of a
surface of a heat exchanger or its component to thereby form a
fluoride layer on a surface layer portion of the heat exchanger or
its component.
[0045] (28) A method of manufacturing a heat exchanger,
comprising:
[0046] a heating step for heating a heat exchanger component in an
atmosphere containing a fluorination processing gas; and
[0047] a fixing step for fixing the component processed by the
heating step to a predetermined position of the heat exchanger.
[0048] (29) The method of manufacturing a heat exchanger as recited
in the aforementioned item (28), further comprising a catalyst
containing layer forming step for forming a layer containing
catalyst on a surface of the component processed by the heating
step.
[0049] (30) A method of manufacturing a heat exchanger,
comprising:
[0050] a fluorine implanting step for implanting an ionized
fluorine into at least a part of a surface of a heat exchanger
component; and
[0051] a fixing step for fixing the component processed by the
fluorine implanting step to a predetermined position of the heat
exchanger.
[0052] (31) The method of manufacturing a heat exchanger according
to the aforementioned item (30), further comprising a catalyst
containing layer forming step for forming a layer containing
catalyst on a portion of the surface of the component processed by
the fluorine implanting step to which the fluorine is
implanted.
[0053] (32) A method of manufacturing a heat exchanger,
comprising:
[0054] a heating step for heating a heat exchanger assembly in an
atmosphere containing a fluorination processing gas, wherein the
heat exchanger assembly is formed by assembling a plurality of heat
exchanger components and integrally brazing the plurality of heat
exchanger components in an assembled state.
[0055] (33) The method of manufacturing a heat exchanger as recited
in the aforementioned item (32), further comprising a catalyst
containing layer forming step for forming a layer containing
catalyst on a surface of the assembly processed by the heating
step.
[0056] (34) A method of manufacturing a heat exchanger,
comprising:
[0057] a fluorine implanting step for implanting an ionized
fluorine into at least a part of a surface of a heat exchanger
assembly, wherein the heat exchanger assembly is formed by
assembling a plurality of heat exchanger components and integrally
brazing the plurality of heat exchanger components in an assembled
state.
[0058] (35) The method of manufacturing a heat exchanger as recited
in the aforementioned item (34), further comprising a catalyst
containing layer forming step for forming a layer containing
catalyst on a portion of the surface of the assembly processed by
the fluorine implanting step to which the fluorine is
implanted.
[0059] Next, each of the above inventions will be explained.
[0060] According to the aforementioned invention (1), since a
fluoride is generally low in thermodynamic free energy and the
fluoride layer is formed on the surface layer portion of the heat
exchanger component, the component can have a layer
thermodynamically stable on the surface layer portion and therefore
becomes excellent in corrosion resistance. Furthermore, the
adhesion to the layer containing the catalyst (hereinafter referred
to as "catalyst containing layer") which will be mentioned later is
improved. This prevents an exfoliation of the catalyst containing
layer assuredly.
[0061] In the present invention, the "fluoride layer" means a layer
which is substantially made of fluoride. Furthermore, in the
present invention, the "surface layer portion" of the component on
which the fluoride layer is formed includes the surface of the
component. Furthermore, as the component, a metallic component can
be exemplified.
[0062] According to the aforementioned invention (2), the reason
why the thickness of the fluoride layer is set to fall within the
range of from 2 nm to 10 .mu.m is as follows. That is, it the
thickness of the fluoride layer is less than 2 nm, it cannot
function as a corrosion processed layer against water (especially
against hot water). As a result, corrosion occurs in a relatively
short time period. On the other hand, if the thickness of the
fluoride layer exceeds 10 .mu.m, although it may function enough
against a corrosion processed layer against water (especially
against hot water), it takes a considerable time to form the
fluoride layer. As a result, the cost for manufacturing the heat
exchanger increases. Accordingly, it is preferable that the
thickness of the fluoride layer falls within the range of from 2 nm
to 10 .mu.m. It is more preferable that the thickness of the
fluoride layer falls within the range of from 20 nm to 3 .mu.m.
[0063] The thickness of the fluoride layer can be measured by
various methods. For example, the thickness can be easily measured
by a depth profile measurement method using an XPS (X-ray
Photoelectron Spectroscopy).
[0064] According to the aforementioned invention (3), generally,
the fins (especially outer fins) and plates among the various
components constituting a fin-plate type heat exchanger are
components which are required to be excellent in corrosion
resistance. Accordingly, it is preferable that the component to
which a fluoride layer is formed is at least one of the fin
(especially outer fins) and the plate.
[0065] According to the aforementioned invention (4), as the heat
medium, especially, water (including steam), hot water of a room
temperature to 100.degree. C. or a long-life coolant of 80 to
150.degree. C., is preferably used.
[0066] According to the aforementioned invention (5), the heat
exchanger can demonstrate the extremely excellent corrosion
resistance when it is used under a water environment, a vapor
environment or a fuel gas environment of a fuel cell. As a fuel gas
of a fuel cell, a hydrogen (H.sub.2) gas is mainly used, and the
combustion gas includes carbon monoxide (CO) gas, gasoline, alcohol
(e.g., methanol), combustion gas, vapor, etc., as impurities. As a
heat exchanger to be used under a fuel gas environment of a fuel
gas, especially, a plate-fin type heat exchanger is preferably
used. On the other hand, the fin-tube type heat exchanger can be
used as a heat exchanger as a heater core.
[0067] According to the aforementioned present invention (6), the
layer containing catalyst (i.e., catalyst containing layer) may be
a layer essentially made of catalyst, or a layer containing
catalyst and substances other than catalyst. As the catalyst, a
modified catalyst of a fuel cell can be exemplified. Especially, it
is preferable that the catalyst is CO selective-oxidation reaction
catalyst of a CO elimination device of a fuel cell. As this CO
selective-oxidation reaction catalyst, catalyst for accelerating
the reaction of carbon monoxide (CO) contained in a fuel gas of a
fuel cell and oxygen (O.sub.2) (the reaction formula:
CO+(1/2)O.sub.2.fwdarw.CO.sub.2) can be exemplified. By the
function of this catalyst, the reaction of the carbon monoxide (CO)
and the oxygen (O.sub.2) is accelerated, and therefore carbon
dioxide (CO.sub.2) generates efficiently. This increases the purity
of the hydrogen (H.sub.2) gas as a fuel gas. Although Cu--Zn series
catalyst and zeolitic series catalyst can be exemplified as the CO
selective-oxidation reaction catalyst, the catalyst is not limited
to the above in the present invention.
[0068] According to the aforementioned invention (7), a heat
exchanger excellent in corrosion resistance for a fuel cell can be
provided.
[0069] According to the aforementioned invention (8), it is
possible to provide a fin-plate type heat exchanger for a fuel cell
excellent in corrosion resistance and capable of efficiently
eliminating carbon monoxide (CO) contained in a fuel gas of a fuel
cell.
[0070] In the heat exchanger for a fuel cell, the reasons why
carbon monoxide (CO) should be eliminated from the combustion gas
of the fuel cell are as follows. That is, if the carbon monoxide
(CO) contained in the fuel gas of the fuel cell as an impurity is
fed into the fuel cell, there are such possibilities that the
performance of the fuel cell may deteriorate and that the carbon
monoxide (CO) may be discharged into the atmospheric air as a
harmful gas as it is. In order to eliminate the carbon monoxide
(CO) from the fuel gas, the catalyst containing layer is formed on
the surface of the fluoride layer. Furthermore, according to the
heat exchanger for a fuel cell, it is possible to set the
temperature of the fuel gas to the temperature at which the
catalyst can demonstrate the function efficiently.
[0071] According to the aforementioned invention (9), since the
substrate of the component is substantially made of aluminum or its
alloy, the heat conductivity becomes high and the heat exchange
performance of the aforementioned heat exchanger improves.
Furthermore, the heat exchanger becomes light in weight.
[0072] According to the aforementioned invention (11), in cases
where the substrate of the components is substantially made of
metal, the fluoride layer is substantially made of the fluoride of
the metal. Concretely, in cases where the substrate of the
component is substantially made of, for example, aluminum or its
alloy, the fluoride layer is substantially made of aluminum
fluoride or aluminum alloy fluoride.
[0073] According to the aforementioned invention (14), the layer
which is substantially made of fluoride generated by performing
forcible oxidation of the surface of the substrate is generally
excellent in corrosion resistance. Accordingly, since the
intermediate layer includes such a layer, the corrosion resistance
is further improved. As the forcible oxidation processing,
anodizing processing which will be explained later can be
exemplified.
[0074] According to the aforementioned invention (15), since the
anodized oxide layer is stable physically and chemically and the
intermediate layer includes the anodized oxide layer, the corrosion
resistance is further improved. The anodized oxide layer can be
formed by various known anodizing processing, and the forming
method is not limited in the present invention. For example, an
anodized oxide layer can be formed on a surface of a component by
subjecting a substrate of the component immersed in an electrolytic
bath containing a predetermined acid such as sulfuric acid, oxalic
acid, chromic acid or these mixed acids to anodizing processing. If
necessary, the anodized oxide layer may be subjected to sealing
processing.
[0075] According to the aforementioned invention (16), since the
fluoride layer is substantially made of fluoride generated by
performing fluorination processing of the surface of the anodized
oxide layer, the corrosion resistance can be further improved.
[0076] According to the aforementioned invention (17), since a
plated layer containing nickel is generally excellent in corrosion
resistance and the fluoride layer is substantially made of fluoride
generated by performing -fluorination processing of the surface of
the plated layer, the corrosion resistance can be further improved.
The terminology "plated layer containing nickel" is used to mean
the "layer containing nickel as a component element" and exclude
the "layer containing nickel as an impurity element". In this case,
the fluoride layer is substantially made of the compound of the
structure element of the plated layer and fluorine. The plated
layer is formed by, for example, an electrolytic plating method or
an electroless plating method. As the plated layer, a nickel plated
layer, a nickel-phosphorus alloy plated layer, a nickel-tungsten
alloy plated layer, a nickel-phosphorus-tungsten alloy plated
layer, a nickel-boron alloy plated layer, a nickel-phosphorus-boron
alloy plated layer and a nickel-copper alloy plated layer can be
exemplified.
[0077] According to the aforementioned invention (18), since the
plated layer is substantially made of electroless nickel plating,
the corrosion resistance can be assuredly improved.
[0078] According to the aforementioned invention (19), since the
plated layer is substantially made of electroless nickel-phosphorus
alloy plating, the corrosion resistance can be assuredly
improved
[0079] According to the aforementioned invention (20), the
corrosion resistance can be further improved. In this case, the
fluoride layer is substantially made of, for example, the compound
of the component element of the plated layer and fluorine. More
specifically, the fluoride layer is made of, for example, nickel
fluoride or nickel-phosphorus alloy fluoride.
[0080] According to the aforementioned invention (21), since the
plated layer is substantially made of electroless nickel plating,
the corrosion resistance can be assuredly improved.
[0081] According to the aforementioned invention (22), since the
plated layer is substantially made of electroless nickel-phosphorus
alloy plating, the corrosion resistance can be assuredly
improved.
[0082] According to the aforementioned invention (23), the fluoride
layer can be easily formed on the surface layer portion of the heat
exchanger or its component. As the fluorination processing gas, a
fluorine (F.sub.2) gas or a fluoride gas (e.g., a nitrogen
trifluoride (ClF.sub.3) gas, a fluorination nitrogen (NF.sub.3)
gas) are preferably used. Furthermore, as the heating means,
although various heating furnaces can be used, especially an
atmospheric heating furnace is preferably used. In the fluorination
method according to the invention, a heat exchanger or its
component is disposed in an atmospheric heating furnace, and a gas
containing a fluorination processing gas is supplied to the
furnace. Then, the heat exchanger or its component is heated in the
atmosphere under predetermined heating processing conditions. By
this, the surface of the heat exchanger or its component reacts to
the fluorination processing gas to thereby form a fluoride layer at
the surface layer portion (including the surface) of the heat
exchanger or its alloy.
[0083] According to the aforementioned invention (24), the reasons
why the concentration of the fluorine gas or that of the fluoride
gas is net so as to fall within the range of from 5 to 80 mass %
are as follows. That is, it the concentration is less than 5 mass
%, the fluoride layer becomes thin, which becomes difficult to
obtain desired corrosion resistance. On the other hand, the more
the concentration increases, the more the formation rate of the
fluoride layer increases. However, if the concentration exceed 80
mass %, the formation rate of the fluoride layer does not increase
so much and will be saturated. Thus, the increase of the
concentration becomes meaningless, and that the manufacturing cost
increases. Accordingly, it is preferable that the concentration
falls within the range of from 5 to 80 mass %. Especially, it is
more preferable that the concentration falls within the range of
from 10 to 60 mass %. Furthermore, as the base gas, various inert
gases such as a nitrogen (N.sub.2) gas, an argon (Ar) gas and a
helium (He) gas can be used. Especially, it is recommended to use a
nitrogen (N.sub.2) gas.
[0084] According to the aforementioned invention (26), the holding
temperature is 100.degree. C. or more and the holding time is 5
hours or more. The reasons are as follows. If the holding
temperature is less than 100.degree. C. or the holding time is less
than 5 hours, the fluorination processing gas hardly diffuses into
the heat exchanger or its component from the surface thereof.
Consequently, a good fluoride layer is not formed. Accordingly, it
is preferable that the holding temperature is 100.degree. C. or
more and the holding time is 5 hours or more. Especially, it is
more preferable that the holding temperature is 150.degree. C. or
more and the holding time is 10 hours or more. Although the upper
limit of the preferable holding time is not specifically limited,
it is preferable that it is 600.degree. C. or less. On the other
hand, although the upper limit of the preferable holding time is
not specifically limited, it is preferable that it is 50 hours or
less. Furthermore, although the holding pressure is not
specifically limited and can be set arbitrary, it is especially
preferable that it falls within the range of from
0.8.times.10.sup.5 to 1.5.times.10.sup.5 Pa.
[0085] According to the aforementioned invention (27), the fluoride
layer can be easily formed at the surface layer portion of the beat
exchanger or its component. This fluorination processing can be
easily executed by, for example, an ion-implantation method using a
known ion implantation equipment. That is, fluorine is ionized with
a filament in a decompressed atmosphere, and the fluorine ion is
implanted into the predetermined portion of the surface of the heat
exchanger or its component. By this, the fluoride layer is formed
at the surface layer portion (including the surface) of the heat
exchanger or its component.
[0086] According to the aforementioned invention (28), it becomes
possible to obtain a heat exchanger excellent in corrosion
resistance.
[0087] According to the aforementioned invention (25), it becomes
possible to obtain a heat exchanger excellent in adhesion of the
layer containing catalyst (i.e., catalyst containing layer).
Accordingly, this heat exchanger is preferably used, especially,
for a fuel cell. As the catalyst, the aforementioned CO
selective-oxidation reaction catalyst of a fuel cell can be
exemplified.
[0088] According to the aforementioned invention (30), it becomes
possible to obtain a heat exchanger excellent in corrosion
resistance.
[0089] According to the aforementioned invention (31), it becomes
possible to obtain a beat exchanger excellent in adhesion of the
catalyst containing layer. Accordingly, this heat exchanger is
preferably used, especially, for a fuel cell. As the catalyst, the
aforementioned CO selective-oxidation reaction catalyst of a fuel
cell can be exemplified.
[0090] According to the aforementioned invention (32), it becomes
possible to obtain a heat exchanger excellent in corrosion
resistance. In general, in cases where components are brazed with
each other after the formation of fluoride layer at the surface
layer portion of the component, the fluoride layer may be damaged
at the time of joining However, according to the present invention,
it becomes possible to prevent such a damage of the fluoride
layer.
[0091] According to the aforementioned invention (33), it becomes
possible to obtain a heat exchanger excellent in adhesion of the
catalyst containing layer. Furthermore, the damage of the catalyst
containing layer can be prevented. Accordingly, this heat exchanger
is preferably used, especially, for a fuel cell. As the catalyst,
the aforementioned CO selective-oxidation reaction catalyst of a
fuel cell can be exemplified.
[0092] According to the aforementioned invention (34), it becomes
possible to obtain a heat exchanger excellent in corrosion
resistance. Furthermore, it becomes possible to prevent such a
damage of the fluoride layer.
[0093] According to the aforementioned invention (35), it becomes
possible to obtain a heat exchanger excellent in adhesion of the
catalyst containing layer. Furthermore, the damage of the catalyst
containing layer can be prevented. Accordingly, this heat exchanger
is preferably used, especially, for a fuel cell. As the catalyst,
the aforementioned CO selective-oxidation reaction catalyst of a
fuel cell can be exemplified.
BRIEF DESCRIPTION OF TIM DRAWINGS
[0094] FIG. 1 is a perspective view showing an example of a
tin-plate type heat exchanger to which the fluorination processing
method according to the present invention is applied.
[0095] FIG. 2 is a cross-sectional perspective view showing a
principal portion for explaining the internal structure of the heat
exchanger.
[0096] FIG. 3 is an enlarged cross-sectional view showing the heat
exchanger component obtained in Example 1.
[0097] FIG. 4 is an enlarged cross-sectional view showing the heat
exchanger component obtained in Example 2.
[0098] FIG. 5 is an enlarged cross-sectional view showing the heat
exchanger component obtained in Example 3.
[0099] FIG. 6 is an enlarged cross-sectional view showing the heat
exchanger component obtained in Example 4.
[0100] FIG. 7 is an enlarged cross-sectional view showing the heat
exchanger component obtained in Example 6.
BEST MODE FOR CARRYING OUT THE PRESENT INVENTION
[0101] The present invention will be explained according to the
attached drawings in order to detail the present invention.
[0102] In FIG. 1, the reference numeral "30" denotes a heat
exchanger as an example to which the fluorination processing method
according to the present invention is applied. This heat exchanger
30 is a fin-plate type heat exchanger for a fuel cell which is used
under a fuel gas environment of a fuel cell, and more specifically
is used as a modification device of a fuel cell. In this figure,
the reference numeral "42" denotes a fuel gas of a fuel cell, and
"43" denotes heat medium. A hydrogen (H.sub.2) gas is used as the
aforementioned fuel gas 42. A refrigerant is used as the
aforementioned heat medium 43. For example, a long-life coolant is
used suitably.
[0103] As shown in FIGS. 1 and 2, this heat exchanger 30 is
provided with a plurality of plate-like tubes 34 each formed by
coupling a pair of pan-like plates 33 and 33 in a face-to-face
manner. The plate-like tubes 34 are stacked one on another with a
corrugated outer fin 31 intervened therebetween. Each of the
plate-like tubes 34 is provided with a flat heat medium passage 35
(refrigerant passage) therein as shown in FIG. 2. In this heat
medium passage 35, a corrugated inner fin 32, which is a member
separated from the plate 33, is disposed. Furthermore, as shown in
FIG. 1, at the end portions of the adjacent plates 33 of the
adjacent plate-like tubes 34, short cylindrical tank portions 36
are formed. Both the tank portions 36 and 36 are engaged with each
other. Furthermore, at both sides of the plurality of plate-like
tubes 34 in the stack direction, side plates 37 and 37 for
protecting the outermost outer fins 31 are disposed. To one of the
side plates 37, a heat medium inlet pipe (refrigerant inlet pipe)
38 is connected. To the other side plate 37, a heat medium outlet
pipe (refrigerant outlet pipe) 39 is connected.
[0104] In this heat exchanger 30, the heat medium 43 is introduced
into one of the tank portion groups 36 via the heat medium inlet
pipe 38. And then, as shown in FIG. 2, the introduced heat medium
43 passes through the heat medium passages 35 of the plurality of
plate-like tubes 34 to reach the other tank portion groups 36.
Thereafter, the heat medium is discharged through the heat medium
outlet pipe 39. On the other hand, the fuel gas 42 (i.e., hydrogen
(H.sub.2) gas) of a fuel cell passes through the gap 40
(hereinafter referred to as "fuel gas passage") of the adjacent
plate-like tubes 34 and 34 in which the outer fin 31 is disposed.
In this heat exchanger 30, heat exchange is performed between the
fuel gas 42 and the heat medium 43 when the fuel gas 42 passes
through the fuel gas passage 40, thereby cooling the fuel gas
42.
[0105] This heat exchanger 30 is manufactured as follows. That is,
the heat exchanger assembly shown in FIG. 1 is provisionally
assembled by using the outer fins 31, the inner fins 32, the plates
33 and the side plates 37. Thereafter, this provisional assembly is
held and tightened using stainless jigs (not shown) and
bolts-and-nuts (riot shown). Then, in this assembled state, the
aforementioned outer fins 31, the inner fins 32, the plates 33 and
the side plates 37 are integrally brazed (i.e., vacuum brazed) in a
vacuum heating furnace. Subsequently, the heat medium inlet pipe 38
and the heat medium outlet pipe 39 are joined by welding to the
side plates 37 and 37 of the assembly respectively. Thus, the
aforementioned heat exchanger 30 is manufactured.
[0106] In the aforementioned heat exchanger 30, the outer fins 31,
the inner fins 32, the plates 33 and the like correspond to the
components of the heat exchanger 30.
[0107] The method of fluorination processing according to the
present invention was applied to the aforementioned heat exchanger
30. The examples are shown as follows.
EXAMPLE 1
[0108] In order to manufacture the aforementioned heat exchanger
30, the following outer fins 31, the inner fins 32 and the plates
33 were prepared.
[0109] The outer fin 31 and the inner fin 32 were made of a bare
material (thickness: 0.1 mm) of aluminum alloy (material: JIS
A3203), respectively. This bare material was the substrate of the
outer fin 31 and that of the inner fin 32, respectively.
[0110] The plate 33 was made of a clad material (thickness: 0.4 mm,
skin material clad rate: 15%) in which a skin material of aluminum
alloy (material: JIS A4004) was clad on both surfaces of a core
material of aluminum alloy (material: JIS A3003). This clad
material is the core material of the plate 33.
[0111] Thereafter, a heat exchanger assembly was provisionally
assembled by using components including the outer fins 31, the
inner tins 32 and the plates 33, and thereafter the outer fins 31,
the inner fins 32 and the plates 33 were integrally secured while
keeping the assembled state, whereby a predetermined heat exchanger
assembly was manufactured. The securing was performed by brazing
(brazing temperature: about 600.degree. C.) in a vacuum heating
furnace.
[0112] Subsequently, the assembly was disposed in an atmospheric
heating furnace, and a gas (a base gas: nitrogen (N.sub.2) gas)
containing a fluorine (F.sub.2) gas as a fluorination processing
gas was introduced in the furnace, whereby the gas in the furnace
was replaced with the gas containing a fluorine gas (F.sub.2). The
gas concentration of the fluorine in the fluorination processing
gas was set to be 20 mass %. Subsequently, in this fluorination
processing gas atmosphere, the aforementioned assembly was heated
under the conditions of the holding temperature of 260.degree. C.
and the holding time of 24 hours (heating step). By this, both the
surfaces of the outer fin 31, those of the inner fin 32 and those
of the plate 33 of the assembly were fluorinated, and a fluoride
layer was formed on each of the surfaces of these substrates. This
fluoride layer was substantially made of the structural elements of
the substrate and fluorine. More concretely, the fluoride layer was
substantially made of an aluminum alloy fluoride such as aluminum
fluoride
[0113] In the obtained heat exchanger, the thickness of the
fluoride layer of the outer fin 31 and that of the inner fin 32
were 0.3 .mu.m, respectively, and the thickness of the fluoride
layer of the plate 33 was 0.1 .mu.m. The thickness of the fluoride
layer was obtained by a depth profile measurement of the fluoride
element with an XPS.
[0114] FIG. 3 is an enlarged cross-sectional view showing the
component (i.e., the outer fin, the inner fin and the plate) of the
heat exchanger 33 obtained in Example 1. In this figure, the
reference numeral "1" is a substrate of the component, and "10"
denotes a fluoride layer.
EXAMPLE 2
[0115] Outer fins 31, inner fins 32 and plates 33 which were
similar to those in Example 1 were prepared.
[0116] Thereafter, the outer fins 31, the inner fins 32 and the
plates 33 were used as components, and in the same method as in
Example 1, a beat exchanger assembly in which the outer fins 31,
the inner fins 32 and the plates 33 were integrally brazed was
made.
[0117] Thereafter, the assembly was immersed into 15% sulfuric-acid
electrolytic bath to thereby anodize both surfaces of the outer fin
31, those of the inner fin 32 and those of the plate 33 of the
assembly. Thus, a sulfuric-acid anodized oxide layer (5 .mu.m in
thickness) as an intermediate layer was formed on the surface of
these substrates.
[0118] Next, this assembly was heated in a fluorination processing
gas atmosphere to fluorinate both surfaces of the outer fin 31,
those of the inner fin 32 and those of the plate 33 of the
assembly. Thus, a fluoride layer was formed on the surface of the
sulfuric-acid anodized oxide layer of each of these substrates. In
this case, the fluorination processing conditions are the same as
those of the aforementioned Example 1. This fluoride layer was
substantially made of a compound of the structure elements of the
sulfuric-acid anodized oxide layer and fluorine. More concretely,
the fluoride layer was substantially made of an aluminum alloy
fluoride.
[0119] In the obtained heat exchanger, the fluoride layer of the
outer fin 31 and that of the inner fin 32 were 0.3 .mu.m in
thickness, respectively, and the fluoride layer of the plate 33 was
0.1 .mu.m in thickness.
[0120] FIG. 4 is an enlarged cross-sectional view showing the
structural member of the heat exchanger obtained in Example 2. In
this figure, the reference numeral "1" denotes a substrate of the
structural member, "3" denotes an anodized oxide layer as an
intermediate layer 2, and "10" denotes a fluoride layer.
EXAMPLE 3
[0121] Outer fins 31, inner fins 32 and plates 33 which were
similar to those in Example 1 were prepared.
[0122] Thereafter, the outer fins 31, the inner fins 32 and the
plates 33 were used as components, and in the same method as in
Example 1, a heat exchanger assembly in which the outer fins 31,
the inner fins 32 and the plates 33 were integrally brazed was
made.
[0123] Thereafter, both surfaces of the outer fin 31, those of the
inner fin 32 and those of the plate 33 of the assembly were
processed by a known electroless plating method, whereby an
electroless nickel plated layer (5 .mu.m in thickness) as an
intermediate layer was formed on the surface of each of the
substrates. The concrete steps of the electroless plating method
employed here will be explained as follows. That is, the assembly
was subjected to degreasing processing with a degreasing liquid of
an alkali family, and then subjected to zincate processing (main
ingredients: NaOH, ZnO) as pretreatment to thereby form a zinc
layer on the surface of the substrate. Subsequently, the assembly
was immersed in a plating bath of 90.degree. C. including sodium
hypophosphite and nickel sulfate as main ingredients, which is
commercially available chemicals, to cause reactions for a
predetermined time. Thus, an electroless nickel plated layer was
formed on the surface of the substrate.
[0124] Next, this assembly was heated in a fluorination processing
gas atmosphere to fluorinate both surfaces of the outer fin 31,
those of the inner fin 32 and those of the plate 33 of the
assembly. Thus, a fluoride layer was formed on the surface of the
electroless nickel plated layer of each of these substrates. In
this case, the fluorination processing conditions are the same as
those of the aforementioned Example 1. This fluoride layer was
substantially made of a compound of the structure elements of the
electroless nickel plated layer and fluorine. More concretely, the
fluoride layer was substantially made of fluoride of nickel such as
nickel fluoride.
[0125] In the obtained heat exchanger, the fluoride layer of the
outer fin 31 and that of the inner fin 32 were 4 .mu.m in
thickness, respectively, and the fluoride layer of the plate 33 was
also 4 .mu.m in thickness.
[0126] FIG. 5 is an enlarged cross-sectional view showing the
structural member of the heat exchanger obtained in Example 3. In
this figure, the reference numeral "1" denotes a substrate of the
structural member, "4" denotes an electroless nickel plated layer
as an intermediate layer 2, and "10" denotes a fluoride layer.
EXAMPLE 4
[0127] Outer fins 31, inner fins 32 and plates 33 which were
similar to those in Example 1 were prepared.
[0128] Thereafter, the outer fins 31, the inner fins 32 and the
plates 33 were used as components, and in the same method as in
Example 1, a heat exchanger assembly in which the outer fins 31,
the inner fins 32 and the plates 33 were integrally brazed was
made.
[0129] Thereafter, the assembly was immersed into 15% sulfuric-acid
electrolytic bath to thereby anodize both surfaces of the outer fin
31, those of the inner fin 32 and those of the plate 33 of the
assembly. Thus, a sulfuric-acid anodized oxide layer (5 .mu.m in
thickness) as an intermediate layer was formed on the surface of
these substrates.
[0130] Thereafter, both surfaces of the outer fin 31, those of the
inner fin 32 and those of the plate 33 of the assembly were
processed by a known electroless plating method, whereby an
electroless nickel plated layer (5 .mu.m in thickness) as an
intermediate layer was formed on the surface of each of the
substrates. The concrete steps of the electroless plating method
employed here were the same as in the aforementioned Example 3.
[0131] Next, this assembly was heated in a fluorination processing
gas atmosphere to fluorinate both surfaces of the outer fin 31,
those of the inner fin 32 and those of the plate 33 of the
assembly. Thus, a fluoride layer was formed on the surface of the
electroless nickel plated layer of each of these substrates. In
this easer the fluorination processing conditions are the same as
those of the aforementioned Example 1. This fluoride layer was
substantially made of compounds of the structure elements of the
electroless nickel plated layer and the fluorine. More concretely,
the fluoride layer was substantially made of fluoride of nickel
such as nickel fluoride.
[0132] In the obtained heat exchanger, the fluoride layer of the
outer fin 31 and that of the inner fin 32 were 4 .mu.m in
thickness, respectively, and the fluoride layer of the plate 33 was
also 4 .mu.m in thickness.
[0133] FIG. 6 is an enlarged cross-sectional view showing the
structural member of the heat exchanger obtained in Example 4. In
this figure, the reference numeral "1" denotes a substrate of the
structural member, "3" denotes an anodized oxide layer, "4" denotes
an electroless nickel plated layer and "10" denotes a fluoride
layer. In this Example 4, the intermediate layer 2 is composed of
the anodized oxide layer 3 and the electroless nickel plated layer
4.
[0134] <<Corrosion Resistant Tests>>
[0135] In order to evaluate the corrosion resistance of the heat
exchangers of Examples 1 to 4, the following plate-like test pieces
(dimension: 50.times.100 mm) were prepared.
[0136] <Test Pieces 1A and 1B>
[0137] The test piece 1A was a piece in which a substrate having
the same material and thickness as those of the outer fin and the
inner fin was subjected to the same processing as in Example 1.
[0138] The test piece 1B was a piece in which a substrate having
the same material and thickness as those of the plate was subjected
to the same processing as in Example 1.
[0139] <Test pieces 2A and 2B>
[0140] The test piece 2A was a piece in which a substrate having
the same material and thickness as those of the outer fin and the
inner fin was subjected to the same processing as in Example 2.
[0141] The test piece 2B was a piece in which a substrate having
the same material and thickness as those of the plate was subjected
to the same processing as in Example 2.
[0142] <Test Pieces 3A and 3B>
[0143] The test piece 3A was a piece in which a substrate having
the same material and thickness as those of the outer fin and the
inner fin was subjected to the same processing as in Example 3.
[0144] The test piece 3B was a piece in which a substrate having
the same material and thickness as those of the plate was subjected
to the same processing as in Example 3.
[0145] <Test Pieces 4A and 4B>
[0146] The test piece 4A was a piece in which a substrate having
the same material as that of the outer fin and the inner fin was
subjected to the same processing as in Example 4.
[0147] The test piece 4B was a piece in which a substrate having
the same material and thickness as those of the plate was subjected
to the same processing as in Example 4.
[0148] <Test Pieces 5A and 5B>
[0149] The test piece SA was a piece in which only a sulfuric-acid
anodized oxide layer was formed on a substrate having the same
material and thickness as those of the outer fin and the inner
fin.
[0150] The test piece 5B was a piece in which only a sulfuric-acid
anodized oxide layer was formed on a substrate having the same
material and thickness as those of the plate.
[0151] <Test Piece 6>
[0152] The test piece 6 was a piece in which no layer was formed on
a substrate of stainless steel (material: SUS304).
[0153] The aforementioned test pieces 1A to 6 were subjected to the
following corrosion test.
[0154] Each of the aforementioned test pieces 1A to 6 were
subjected to the test 150 times (cycles), wherein the test includes
a step of immersing each test piece 1A to 6 in a corrosion water
solution (ordinary temperature) of PH=1.3 containing hydrochloric
acid, sulfuric acid, nitric acid, formic acid and acetic acid, a
step of holding the test piece taken out of the corrosion water
solution for twenty minutes in a 200.degree. C. high temperature
furnace and a step of immersing the test piece in the corrosion
water solution again after cooling it to approximately ordinary
temperature. Thereafter, the decreased amount of the thickness and
the decreased amount of weight due to the corrosion of each test
piece was examined.
[0155] The results of the aforementioned corrosion test are shown
in Table 1.
1 Corrosion test Existence of (150 cycles) Fluorination Thickness
Material of processing decreased Overall Substrate Intermediate
layer layer amount (.mu.m) evaluation Test piece 1A A3203 -- Yes
0.4 .circleincircle. Test piece 1B Clad -- Yes 1.2 .circleincircle.
material Test piece 2A A3203 Sulfuric-acid anodized Yes 3.2
.largecircle. oxide layer Test piece 2B Clad Sulfuric-acid anodized
Yes 4.1 .largecircle. material oxide layer Test piece 3A A3203
Electroless nickel plated Yes 1.3 .circleincircle. layer Test piece
3B Clad Electroless nickel plated Yes 1.1 .circleincircle. material
layer Test piece 4A A3203 Sulfuric-acid anodized Yes 1.3
.circleincircle. oxide layer and Electroless nickel plated layer
Test piece 4B Clad Sulfuric-acid anodized material oxide layer and
Electroless Yes 1.1 .circleincircle. nickel plated layer Test piece
5A A3203 Sulfuric-acid anodized No 9.1 X oxide layer Test piece 5B
Clad Sulfuric-acid anodized No 8.9 X material oxide layer Test
piece 6 Stainless -- No 0.8 .circleincircle. steel
[0156] In the column of "Overall Evaluation" of the corrosion test
in Table 1, "{circle over (.smallcircle.)}" denotes "almost no
corrosion," ".largecircle." denotes "slight corrosion," and
".times." denotes "heavy corrosion."
[0157] According to the results of the corrosion tests shown in
Table 1, it is confirmed that the test pieces 1A to 4B are
excellent in corrosion resistance. Accordingly, it is confirmed
that the heat exchanger according to Examples 1 to 4 are excellent
in corrosion resistance. Especially, it is confirmed that the test
pieces 1A, 1B, 3A, 3B, 4A and 4B are extremely excellent in
corrosion resistance. Accordingly, it is confirmed that the heat
exchanger according to Examples 1, 3 and 4 are extremely excellent
in corrosion resistance.
[0158] Accordingly, the heat exchanger according to the present
invention can be used for a long time period under a fuel cell gas
environment in which a long time usage was used to be difficult.
Furthermore, even under the water environment or vapor environment,
it is possible to use the heat exchanger for a long time period.
Furthermore, in cases where water is used as heat medium, the heat
exchanger can be used for a long time period.
EXAMPLE 5
[0159] Outer fins 31, inner fins 32 and plates 33 which were
similar to those in Example 1 were prepared.
[0160] Thereafter, the outer fins 31, the inner fins 32 and the
plates 33 were used as components, and in the same method as in
Example 1, a heat exchanger assembly in which the outer fins 31,
the inner fins 32 and the plates 33 were integrally brazed was
made.
[0161] Subsequently, ionized fluorine was implanted on both
surfaces of the outer fin 31, the outer fin side surface of the
plate 33 (fluorine implanting step). By this, a fluoride layer was
formed on the surfaces of these substrates. The fluorination
processing procedures by the ion implantation method will be
detailed as follows. That is, ionized fluorine was implanted on the
surfaces of the substrates by making the substrates negative in a
fluorine gas (F.sub.2) and performing a glow discharge with the
energy of 1 MeV. By this, the surfaces of the substrates were
fluorinated
[0162] In the obtained heat exchanger, the fluoride layer of the
outer fin 31 was 0.3 .mu.m in thickness, and the fluoride layer of
the plate 33 was 0.1 .mu.m in thickness.
EXAMPLE 6
[0163] Outer fins 31, inner fins 32 and plates 33 which were
similar to those in Example 1 were prepared.
[0164] Thereafter, the outer fins 31, the inner fins 32 and the
plates 33 were used as components, and in the same method as in
Example 1, a heat exchanger assembly in which the outer fins 31,
the inner fins 32 and the plates 33 were integrally brazed was
made.
[0165] Thereafter, both surfaces of the outer fin 31, those of the
inner fin 32 and those of the plate 33 of the assembly were
processed by a known electroless plating method, whereby an
electroless nickel-phosphorus alloy plated layer (10 .mu.m in
thickness) as an intermediate layer was formed on the surface of
each of the substrates.
[0166] Next, this assembly was healed in a fluorination processing
gas atmosphere to fluorinate both surfaces of the outer fin 31,
those of the inner fin 32 and those of the plate 33 of the
assembly. Thus, a fluoride layer was formed on the surface of the
electroless nickel-phosphorus alloy plated layer of each of these
substrates. In this case, the fluorination processing conditions
are the same as those of the aforementioned Example 1. This
fluoride layer was substantially made of compounds of the structure
elements of the electroless nickel-phosphorus alloy plated layer
and the fluorine. More concretely, the fluoride layer was
substantially made of a nickel-phosphorus alloy fluoride.
[0167] In the obtained heat exchanger, the fluoride layer of the
outer fin 31 and that of the inner fin 32 were 0.3 .mu.m in
thickness, and the fluoride layer of the plate 33 was also 0.1
.mu.m in thickness.
[0168] Next, on both surfaces of the outer fin 31 and the outer fin
side surface of the plate 33 which were the portion to which a fuel
gas (i.e., hydrogen (H.sub.2) gas) of a fuel cell, a layer
containing the aforementioned catalyst (thickness: 100 .mu.m) was
formed by applying and baking CO selective-oxidation reaction
catalyst thereto. The catalyst was used to promote the reaction of
the carbon monoxide (CO) contained in the fuel gas of the fuel cell
and oxygen (O.sub.2).
[0169] FIG. 7 is an enlarged cross-sectional view showing the
structural members (outer fin, plate) of the heat exchanger
obtained in Example 6. In this figure, the reference numeral "1"
denotes a substrate of the structural member, "4" denotes an
electroless nickel-phosphorus alloy plated layer as an intermediate
layer 2, and "10" denotes a fluoride layer and "15" is a catalyst
containing layer.
[0170] Next, in order to evaluate the corrosion resistance of the
heat exchanger of Example 6, corrosion tests were performed under
the same conditions as in the aforementioned <<Corrosion
resistance tests>>. As a result, it is confirmed that this
heat exchanger is extremely excellent in corrosion resistance.
[0171] Furthermore, in the heat exchanger of Example 6, the
catalyst containing layer 15 was formed on and firmly adhered to
the surface of the fluoride layer 10. Accordingly, this reveals
that the heat exchanger can be used for a long time period under a
fuel gas environment of a fuel cell.
[0172] Although some embodiments of the present invention are
explained, the present invention is not limited to these
embodiments and can be changed in various manners.
[0173] For example, the inner fin 32 and the plate 33 may be
integrally formed.
[0174] Furthermore, in manufacturing a heat exchanger, structural
components (outer fin, inner fin, plate, etc.) of the heat
exchanger may be heated in an atmosphere containing a fluorination
processing gas (heating step) to form a fluoride layer on the
surface layer portion of the structural components, and then the
structural components may be fixed to predetermined positions of
the heat exchanger.
[0175] Furthermore, in manufacturing a heat exchanger, ionized
fluorine may be implanted on the surfaces of structural components
(outer fin, inner fin, plate, etc.) of the heat exchanger (fluorine
implanting step) to form a fluoride layer on the surface layer
portion of the structural components, and then the structural
components may be fixed to predetermined positions of the heat
exchanger.
[0176] As mentioned above, the present invention will be summarized
as follows.
[0177] Since the heat exchanger according to the present invention
includes heat exchanger structural components in which fluoride
layer is formed on the surface layer portion, the heat exchanger is
excellent in corrosion resistance as compared with prior heat
exchangers, and can be suitably used as a heat exchanger using
water as heat medium, especially a heat exchanger using hot water
or water containing long-life coolant. Furthermore, the heat
exchanger can also be preferably used as a heat exchanger to be
used under the conditions of water environment, vapor environment
or fuel gas environment of a fuel cell.
[0178] According to the method of fluorinating a heat exchanger or
its components of the present invention, a fluoride layer can be
easily formed on the surface layer portion of the heat exchanger or
its components.
[0179] Furthermore, in cases where the concentration of the
fluorine gas or that of the fluoride gas is set to fall within a
predetermined range, it is possible to assuredly form a fluoride
layer excellent in corrosion resistance on the surface layer
portion of the heat exchanger or its components.
[0180] According to the method of manufacturing a heat exchanger of
the present invention, a heat exchanger excellent in corrosion
resistance can be obtained. The obtained heat exchanger can be
suitably used as a heat exchanger using water as heat medium,
especially a heat exchanger using hot water or water containing
long-life coolant. Furthermore, the heat exchanger can also be
preferably used as a heat exchanger to be used under the conditions
of water environment, vapor environment or fuel gas environment of
a fuel cell.
INDUSTRIAL APPLICABILITY
[0181] The heat exchanger according to the present invention can be
preferably used for, for example, an evaporator, a condenser, a
radiator, an oil cooler, especially for a heat exchanger for a fuel
cell.
[0182] The method of fluorinating a beat exchanger or its
components can be preferably applied to a heat exchanger to be used
as, for example, an evaporator, a condenser, a radiator, an oil
cooler or its components, especially to a heat exchanger for a fuel
cell or its components.
[0183] The method of manufacturing a heat exchanger can be
preferably applied to a heat exchanger to be used as, for example,
an evaporator, a condenser, a radiator, an oil cooler or its
components, especially to a heat exchanger for a fuel cell.
[0184] The terms and descriptions in this specification are used
only for explanatory purposes and the present invention is not
limited to these, but many modifications and substitutions may be
made without departing from the spirit of the scope of the present
invention which is defined by the appended claims.
* * * * *