JP2011241448A - Aluminum alloy clad material excellent in alkali resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy clad material which has sufficient corrosion resistance even in a high-temperature and alkaline environment and causes no through pitting corrosion at an early stage.SOLUTION: The aluminum alloy clad material has a core material whose one face is cladded with a brazing filler metal and whose other face is cladded with a sacrificial material. The sacrificial material is an aluminum alloy comprising, by mass: 1.0-8.0% Zn, one or more elements selected from 0.85-1.5% Fe, 0.85-1.5% Ni, 0.85-2.0% Si, 0.2-0.5% Cu and 0.01-0.05% Ti, and the balance being Al and unescapable impurities. In this case, the cathode current density of the brazing filler metal is 20 μA/cmor below at the natural potential of the sacrificial material shown in a corrosion liquid with a pH value of 9-11 at a temperature of 80-100°C.

Description

  The present invention relates to an aluminum alloy clad material exhibiting excellent corrosion resistance in a high temperature and highly alkaline environment such as the inside of a tube of an automobile radiator.

  A radiator which is one of the conventional aluminum heat exchangers for automobiles is shown in FIGS. The automobile heat exchanger of FIG. 3 assembles the core (11) by disposing the fins (9) on the tube (8) through which the cooling water passes and attaching the header plates (10) to both ends of the tube (8). After brazing the core, the resin tanks (12A) and (12B) are attached to the header plate (10) via the backing (13) to form a radiator. As the cooling water for the radiator, a weak alkaline aqueous solution containing an antifreeze, so-called long life coolant (LLC) or the like is used.

  As the material for the fin (9), a plate material having a thickness of around 0.1 mm obtained by adding 1.50 mass% of Zn to JIS3003 alloy is used. In order to prevent the occurrence of through-pitting corrosion from the cooling water, the tube (8) is clad with JIS3003 alloy as a core material, JIS7072 alloy as a sacrificial anode material on the cooling water side, and JIS4343 alloy on the outside air side. An aluminum alloy clad material having a thickness of about 0.2 to 0.4 mm clad is used as the brazing material. The header plate (10) is made of an aluminum alloy clad material having a thickness of about 1.0 to 1.3 mm and the same configuration as the tube (8).

  The aluminum alloy clad material used for the tube (8) and the header plate (10) is exposed to an atmosphere of about 600 ° C. during brazing heating. For this reason, Zn added to the sacrificial anode material forms a Zn diffusion layer in the core material. It is known that the presence of this Zn diffusion layer causes the corrosion generated in the sacrificial anode material to spread laterally even after reaching the core material, so that no through-hole is formed over a long period of time.

  As such sacrificial anode materials, Al—Zn—Mg alloys and Al—Zn—In alloys are known in addition to JIS7072 alloys. It is known that the corrosion of the sacrificial anode material spreads laterally when these alloys are used for the aluminum alloy clad composite material as well as the JIS7072 alloy.

  By the way, as the cooling water for the radiator of the heat exchanger, a weak alkaline aqueous solution containing an antifreeze solution, so-called LLC, is used as described above. In a tube using an aluminum alloy clad material, there is a problem that a sufficient anticorrosion effect cannot be obtained in such an environment, and through-hole corrosion occurs early.

  On the other hand, in Patent Documents 1 and 2, in an aluminum alloy clad material in which a brazing material is clad on one surface of a core material and a sacrificial anode material is clad on the other surface, the sacrificial anode material is combined with Al to form a sacrificial anode. An aluminum alloy clad material characterized in that it contains an element that forms a noble compound from the matrix of the material and is composed of an aluminum alloy composed of the balance Al and impurities has been proposed.

In these aluminum alloy clad materials, the deposition of aluminum hydroxide, which is a film component, is prevented where the compound exists on the surface of the sacrificial anode material, and the formation of the film is suppressed, and small film defects increase and pitting corrosion occurs. It is supposed to be distributed. Therefore, the progress of localized pitting corrosion in the depth direction is suppressed as in the case where there are few film defects, and the occurrence of through pitting corrosion can be prevented even in an alkaline corrosion environment.
However, there is a problem that these do not essentially prevent corrosion.

Japanese Patent Laid-Open No. 10-072634 JP-A-11-140571

  In view of the above problems in the prior art, the present invention provides an aluminum alloy clad material that can provide a sufficient anticorrosion effect even in a weak alkaline corrosion environment such as LLC and does not cause penetration corrosion at an early stage. With the goal.

  As a result of detailed investigation of the corrosion occurrence state of the tube using the aluminum alloy clad material in the LLC environment, the present inventors have found that the occurrence of corrosion is remarkable at higher temperatures.

In order to clarify the above cause, a polarization curve was measured using a hot alkaline corrosive solution. As a result, it was found that in this corrosive environment, the cathode current of the brazing material was significantly increased at the natural potential of the sacrificial material. As illustrated in FIG. 4, JISBA4343P is used as a brazing material, JIS7072 alloy is used as a sacrificial material, NaCl: 0.226 g / L, Na ₂ SO ₄ : 0.089 g / L is contained as an alkaline corrosion solution, and hydroxylated. Polarization curves were measured using 90 ° C. aqueous solutions adjusted to pH 11 with an aqueous sodium solution. In this case, the cathode current density of the brazing material at a natural potential of the sacrificial material of about 1100 mV (vs. Ag / AgCl (saturated KCl)) was as high as about 50 μA / cm ² .

This cathode current is based on a reduction reaction of water (2H ₂ O + 2e → H ₂ + 2OH ⁻ ), and generates hydroxide ions. That is, in a high temperature and alkaline corrosive environment, electrons generated by dissolution of the sacrificial anode material tend to concentrate on the brazing material where the cathode reaction is more likely to proceed, leading to a high pH around the brazing material, ie, strong alkalinity. . Since aluminum is an amphoteric metal, it is dissolved by alkali and extreme corrosion proceeds. Therefore, by reducing the cathode current density of the brazing material at the natural potential of the sacrificial material and dispersing the water reduction reaction between the brazing material and the sacrificial material, the extreme environment around the brazing material in a high temperature alkaline corrosion environment is reduced. Corrosion can be suppressed.

  Based on the above findings, the present inventor has proceeded with a study to clarify the requirements for an aluminum alloy clad material exhibiting good corrosion resistance in a high-temperature alkaline corrosion solution. As a result, by adding a certain amount of a specific element to the sacrificial material, the difference between the cathode polarization curves of the sacrificial material and the brazing material is reduced, that is, the difference in current density between the sacrificial material and the brazing material at the same electrode potential. By reducing the cathode current density of the brazing material by reducing the thickness of the clad material, and preventing the corrosion of the clad material from being strongly alkalinized. It was.

The aluminum alloy clad material of the present invention has been made based on such knowledge. That is, the present invention is the aluminum alloy clad material according to claim 1, wherein the brazing material is clad on one surface of the core material and the sacrificial material is clad on the other surface, and the sacrificial material is Zn: 1.0-8. 0.0 mass%, Fe: 0.85-1.5 mass%, Ni: 0.85-1.5 mass%, Si: 0.85-2.0 mass%, Cu: 0.2-0.5 mass% And Ti: 0.01-0.05 mass% of one or more of aluminum alloy, the balance being aluminum alloy consisting of Al and inevitable impurities, pH 9-11 in a temperature of 80-100 ℃ corrosive liquid The cathode current density of the brazing material at the natural potential of the sacrificial material shown is 20 μA / cm ² or less.

  According to a second aspect of the present invention, the core material is JIS3003 alloy and the brazing material is any one of JISBA4343P, BA4045P and BA4047P.

  According to the present invention, for example, an aluminum alloy clad material having excellent internal high temperature alkali corrosion resistance is provided as an aluminum alloy tube material of an automotive heat exchanger.

It is a graph which shows the cathode polarization curve of the sacrificial material and brazing material which are used for this invention in high temperature alkaline environment. (A) is a schematic diagram of a specimen cross section of a corrosion test (alkali test), and (b) is a schematic diagram of a corrosion part. (A) is a front view of the heat exchanger (radiator) for motor vehicles currently used conventionally, (b) is the II sectional expanded view of (a). It is a graph which shows the cathode polarization curve of the conventional sacrificial material and brazing material in a hot alkaline environment.

  The aluminum alloy clad material according to the present invention has a configuration in which a brazing material is clad on one surface of a core material made of an aluminum alloy and a sacrificial material is clad on the other surface. Below, the reason for limitation of the material component which comprises this invention is demonstrated. Note that the thickness of such a three-layer clad material is preferably 0.2 to 0.4 mm.

A. Sacrificial material Zn: Zn is dissolved in an aluminum alloy, and in a neutral corrosion environment having a pH of around 7, the natural potential of the sacrificial material is reduced to prevent the core material and improve the corrosion resistance of the tube. Zn is an essential component of the sacrificial material. If it is less than 1.0 mass% (hereinafter simply referred to as “%”), the effect of lowering the natural potential is insufficient. If it exceeds 8.0%, it will dissolve excessively and shorten the penetration life of the tube. Therefore, the addition amount of Zn is defined as 1.0 to 8.0%. More preferably, it is 2.0 to 6.0%.

Fe: Fe forms a solid solution or an Al—Fe compound in an aluminum alloy. In an alkaline corrosive environment, the progress of the cathode reaction (2H ₂ O + 2e → H ₂ + 2OH ⁻ ) is promoted on the surface of this compound, increasing the cathode current of the alloy. If it is less than 0.85%, the cathode current is not sufficient, and if it exceeds 1.5%, the material is cracked by rolling during production. Therefore, the addition amount of Fe is defined as 0.85 to 1.5%. More preferably, it is 1.0 to 1.3%.

  Ni: Ni forms a solid solution or an Al—Ni compound in an aluminum alloy. In an alkaline corrosion environment, as with Fe, the cathodic reaction progresses on the surface of the compound, increasing the cathode current of the alloy. If it is less than 0.85%, the cathode current is not sufficient, and if it exceeds 1.5%, the material is cracked by rolling during production. Therefore, the addition amount of Ni is defined as 0.85 to 1.5%. More preferably, it is 1.0 to 1.3%.

  Si: Si forms a solid solution or an Al—Si—Fe based compound in an aluminum alloy. In an alkaline corrosion environment, as with Fe and Ni, the progress of the cathode reaction on the surface of this compound is promoted, increasing the cathode current of the alloy. If it is less than 0.85%, the cathode current is not sufficient, and if it exceeds 2.0%, the material melts during brazing heating. Therefore, the addition amount of Si is defined as 0.85 to 2.0%. More preferably, it is 1.0 to 1.5%.

  Cu: Cu forms a solid solution or an Al—Cu compound in the aluminum alloy. In an alkaline corrosion environment, as with Fe, Ni and Si, the progress of the cathode reaction is promoted on the surface of this compound, increasing the cathode current of the alloy. If it is less than 0.2%, the cathode current is not sufficient, and if it exceeds 0.5%, the material melts during brazing heating. Therefore, the addition amount of Cu is defined as 0.2 to 0.5%. More preferably, it is 0.3 to 0.4%.

  Ti: Ti forms a solid solution or an Al—Ti compound in the aluminum alloy. In an alkaline corrosion environment, as with Fe, Ni, Si, and Cu, the progress of the cathode reaction is promoted on the surface of this compound, increasing the cathode current of the alloy. If it is less than 0.01%, the cathode current is not sufficient, and if it exceeds 0.05%, self-corrosion is promoted. Therefore, the addition amount of Ti is defined as 0.01 to 0.05%. More preferably, it is 0.02 to 0.03%.

Fe, Ni, Si, Cu and Ti are added singly or in combination of two or more. When adding 1 type, it is necessary to add in the said range prescribed | regulated about the component. When two or more kinds are added, they may be within the range defined for a plurality of components. As a result, the cathode current density of the brazing material at the natural potential of the sacrificial material may be ²⁰ μA / cm ² or less.

In addition, in the aluminum alloy constituting the sacrificial material, as an inevitable impurity, Mn, Mg
, Cr or the like may be contained as an individual component content of 0.05% or less. The clad rate of the sacrificial material is preferably in the range of 5 to 15%.

B. Core Material When forming the clad material in the present invention, JIS3003 alloy is preferably used as the core material, but is not particularly limited, depending on the shape of the heat exchanger and the heating conditions when producing the heat exchanger. Various selections are possible.

C. Brazing material When forming the clad material in the present invention, BA 4343P, BA 4045P, and BA 4047P defined in JIS are suitably used as the brazing alloy, but the alloy is not particularly limited, and is a heat exchanger. Various selections are possible depending on the shape and the heating conditions in producing the heat exchanger. The clad rate of the brazing material is preferably in the range of 2 to 12%.

  The core material and the brazing material may also contain unavoidable impurities such as Cr and Ti as individual component contents of 0.05% or less.

  Hereinafter, embodiments of the present invention will be described in detail with reference to examples of the present invention, comparative examples, and reference examples.

Invention Examples 1 to 35, Comparative Examples 36 to 61, and Reference Examples 62 to 65
An Al alloy having the composition shown in Tables 1 and 2 is cast to produce an ingot, subjected to homogenization at 560 ° C. for 3 hours, and then hot-rolled to form a hot-rolled sheet having a thickness of 20 mm. A sacrificial material was produced. Similarly, a hot-rolled sheet of a core material made of a JIS3003 alloy having a thickness of 170 mm and a brazing material made of a BA4343P alloy having a thickness of 10 mm was prepared.
A sacrificial material was placed on one surface of the core material, and a brazing material was placed on the other surface and clad by hot rolling, and then cold rolled. In the middle of cold rolling, intermediate annealing was performed at 400 ° C. for 1 hour to obtain a final cold rolling rate of 30%, and a 0.20 mm three-layer aluminum alloy clad material was produced. The clad rate of the sacrificial material was 10%, and the clad rate of the brazing material was 5%.

(1) Measurement of polarization curve Cathode polarization curves were measured for the sacrificial material and the brazing material (BA4343P alloy) produced as described above. The sacrificial material and the brazing material were cut into 15 × 40 mm ² , and the measurement was performed by masking the back surface and the edge part leaving the measurement surface 10 × 10 mm ² . 0.226 g of NaCl and 0.089 g of Na ₂ SO ₄ were dissolved in 1 L of distilled water, and an aqueous NaOH solution was added to an aqueous solution having Cl ⁻ = 195 ppm and SO ₄ ²⁻ = 60 ppm to adjust the pH to 8, 9, 11 And the solution adjusted to 12 was used for the alkaline corrosion liquid. The measurement temperatures were 70, 80, 90 and 100 ° C. From the obtained cathode polarization curve, the cathode current density of the brazing material at the natural potential of the sacrificial material was determined. As an example of the measurement result, the measurement result in Inventive Example 4 is shown in FIG. In FIG. 1, the cathodic polarization curves in the vicinity of the natural potential of the sacrificial material and the brazing material overlap to make the natural potentials equal, and the cathode current density of the brazing material is zero.

(2) Alkaline Corrosion Test Two pieces of the three-layer aluminum alloy clad material produced as described above were prepared by cutting them into a width of 30 mm and a length of 50 mm. As shown in FIG. 2, each of the aluminum alloy clad materials 1 has a sacrificial material 3 clad on one surface of a core material 2 and a brazing material 4 clad on the other surface. The brazing material 4 surface of one aluminum alloy clad material 1 and the sacrificial material 3 surface of the other aluminum alloy clad material 1 were shifted about 10 mm and overlapped in the length direction. This was heated under a nitrogen atmosphere and brazed at 600 ° C. for 3 minutes. Next, the exposed portion was masked with a resin tape 5 so that only the sacrificial material 3 surface of both aluminum alloy clad materials 1 and the brazing side of one aluminum alloy clad material 1 were exposed to obtain a test piece.

The test piece prepared in this manner was exposed to the same alkaline corrosion solution (Cl ⁻ = 195 ppm, SO ₄ ²⁻ = 60 ppm, pH 11, temperature 90 ° C.) as the above-mentioned cathodic polarization curve, which was not masked. Was immersed so that the specific liquid amount was 6 mL / cm ² . A cycle test was performed for 3 months in which the immersion time for one time was 8 hours, and then left in the atmosphere for 16 hours. After the test, the cross section of the test piece in the vicinity of the brazed portion 6 was observed, and the maximum corrosion depth in the corroded portion 7 was measured.

  Tables 3 and 4 show the cathode current density of the brazing material obtained by measuring the polarization curve and the maximum corrosion depth obtained by the alkaline corrosion test. In addition, about the maximum corrosion depth, less than 10 micrometers was set as the pass, and more than it was set as the failure.

(3) Rolling workability The presence or absence of cracks in the rolled sheet was visually observed, and when cracks occurred, it was determined that rolling workability was poor.

(4) Brazing property The molten state of the material at the time of brazing heating was visually observed, and when melting occurred, it was determined that the brazing property was poor.

(5) Self-corrosion The presence or absence of a sacrificial material remaining on the cross-section of the specimen was observed with an optical microscope. If the self-corrosion was so large that no residual material was observed, it was determined that self-corrosion was poor. On the other hand, if the amount of Zn added is too small and the natural potential is not sufficiently reduced, and the self-corrosion is too small to function as a sacrificial material, the self-corrosion failure was determined.
Table 4 also shows comparative examples having poor rolling processability, brazing property and self-corrosion property.

In Examples 1-32 of the present invention, the sacrificial material contains specified amounts of Ni, Cu, Ti, Fe, and Si, so that the natural potential of the sacrificial material in an alkaline corrosion liquid having a pH of 11 and a temperature of 90 ° C. The current density of the brazing filler metal was in the range of ²⁰ μA / cm ² or less. As a result, the corrosion depth was 8 μm at the maximum, showing good high-temperature alkaline corrosion resistance, and good rolling workability, brazing property and self-corrosion property.

Examples 33 to 35 of the present invention are examples in which the sacrificial material contains Ni, Cu, Ti, Fe, and Si in specified amounts, and the pH and temperature of the alkaline corrosion liquid are changed within the range specified by the present invention. . In all cases, the current density of the brazing material at the natural potential of the sacrificial material was in the range of ²⁰ μA / cm ² or less. As a result, the corrosion depths were all 0 μm, good high-temperature alkaline corrosion resistance was exhibited, and rolling workability, brazing properties and self-corrosion properties were also good.

In Comparative Examples 36 and 37, the sacrificial material did not contain Ni, Cu, or Ti, and any of the materials containing Fe and Si had too little content, so the current density of the brazing material was 20 μA / cm ² or more. The maximum corrosion depth was rejected.
In Comparative Examples 39 and 40, the sacrificial material did not contain Cu or Ti, and the content of all of the materials containing Fe, Ni, and Si was too small, so that the current density of the brazing material was 20 μA / cm ² or more. The maximum corrosion depth was rejected.
In Comparative Examples 42 and 43, the sacrificial material did not contain Ni, Cu, or Ti, and the content of both Fe and Si was too small, so that the current density of the brazing material was 20 μA / cm ² or more. The maximum corrosion depth was rejected.
In Comparative Examples 45 and 46, the sacrificial material does not contain Ni or Ti, and any of the materials containing Fe, Si, and Cu has too little content, so that the current density of the brazing material is 20 μA / cm ² or more. The maximum corrosion depth was rejected.
In Comparative Example 48, the sacrificial material did not contain Cu, Ti, and any of the materials containing Fe, Ni, and Si had too little content, so the current density of the brazing material became ²⁰ μA / cm ² or more. The maximum corrosion depth was rejected.
In Comparative Examples 52 and 53, the sacrificial material does not contain Ni, Cu, or Ti, and any of the materials containing Fe and Si has too little content, so the current density of the brazing material is 20 μA / cm ² or more. The maximum corrosion depth was rejected.
In Comparative Examples 54 and 55, the sacrificial material did not contain Cu or Ti, and the content of all of the materials containing Fe, Ni, and Si was too small, so the current density of the brazing material was 20 μA / cm ² or more. The maximum corrosion depth was rejected.
In Comparative Example 56, the sacrificial material does not contain Ni, Cu, or Ti, and any of the materials containing Fe and Si has too little content, so that the current density of the brazing material is 20 μA / cm ² or more. The maximum corrosion depth was rejected.

In Comparative Example 38, the sacrificial material did not contain Ni, Cu, or Ti, but contained Fe and Si. However, since the Fe content was too large, the maximum corrosion depth was acceptable but the rolling processability was improved. It was inferior.
In Comparative Example 41, the sacrificial material did not contain Cu or Ti, but contained Fe, Ni, and Si, but because the Ni content was too large, the maximum corrosion depth was acceptable but the rolling processability was improved. It was inferior.
In Comparative Example 44, the sacrificial material did not contain Ni, Cu, Ti, and contained Fe and Si, but the Si content was too high, so the maximum corrosion depth was acceptable but the brazing property was inferior. It was.
In Comparative Example 47, the sacrificial material did not contain Ni and Ti, but contained Fe, Si, and Cu. However, since the Cu content was excessive, the maximum corrosion depth was acceptable, but the brazing property was improved. It was inferior.
In Comparative Example 49, the sacrificial material does not contain Cu, but contains Fe, Ni, Si, and Ti. However, since the Ti content is excessive, self-corrosion is excessively large so that local corrosion is not apparent. Met.
In Comparative Example 50, since the Zn content, which is an essential component of the sacrificial material, was too small, the natural potential was not sufficiently reduced and the function as the sacrificial material was insufficient.
In Comparative Example 51, since the Zn content, which is an essential component of the sacrificial material, was too much, self-corrosion was excessive so that local corrosion was not apparent.

Comparative Examples 57-59 are sacrificial materials that do not contain Ni, Cu, Ti, and alloys containing Fe and Si that are too low in content (Comparative Example 36). This is an example in which the pH and temperature of the alkaline corrosion liquid are changed. In either case, the current density of the brazing material at the natural potential of the sacrificial material was 20 μA / cm ² or more, and the maximum corrosion depth was unacceptable.

  Comparative Example 60 is a sacrificial material that does not contain Ni, Cu, or Ti, and an alloy that contains Fe and Si and has too little content (Comparative Example 36). This is an example in which the pH of the alkaline corrosion liquid is increased. Apparently, self-corrosion was excessive so that local corrosion was not observed.

  Comparative Example 61 is an example in which the pH of the alkaline corrosive liquid was increased to a value outside the range defined by the present invention in an alloy containing a specified amount of Ni, Cu, Ti, Fe, and Si in the sacrificial material (Example 2 of the present invention). is there. Apparently, self-corrosion was excessive so that local corrosion was not observed.

  In Comparative Examples other than Comparative Examples 38, 41, 44, 47, 49, and 51, the rolling processability, brazing property, and self-corrosion property were good.

Reference examples 62 and 63 are sacrificial materials that do not contain Ni, Cu, or Ti, and those containing Fe and Si that are too low in content (Comparative Example 36). This is an example in which the pH or temperature of the alkaline corrosion liquid is lowered to the outside. In either case, the corrosive environment became milder, and the current density of the brazing material at the natural potential of the sacrificial material was within a range of ²⁰ μA / cm ² or less. As a result, the corrosion depth was 0 μm and good high-temperature alkaline corrosion resistance was exhibited.

In Reference Examples 64 and 65, the pH or temperature of the alkaline corrosive solution is outside the range defined by the present invention in an alloy containing a specified amount of Ni, Cu, Ti, Fe and Si (Invention Example 2) in the sacrificial material. This is a reduced example. In either case, the corrosive environment became milder, and the current density of the brazing material at the natural potential of the sacrificial material was within a range of ²⁰ μA / cm ² or less. As a result, the corrosion depth was 0 μm, and good high-temperature alkaline corrosion resistance was exhibited.

  According to the present invention, for example, as an aluminum alloy piping material of an automotive heat exchanger, an aluminum alloy clad material having excellent alkali corrosion resistance inside is obtained, and the durability of the heat exchanger is remarkably improved. There is an outstanding effect.

DESCRIPTION OF SYMBOLS 1 ... Aluminum alloy clad material 2 ... Core material 3 ... Sacrificial material 4 ... Brazing material 5 ... Resin tape 6 ... Brazing part 7 ... Corrosion part 8 ... Tube 9 ... Fins 10 ... Header plate 11 ... Core 12A, 12B ... Resin tank 13 ... Backing

Claims (2)

An aluminum alloy clad material in which a brazing material is clad on one surface of a core material and a sacrificial material is clad on the other surface, the sacrificial material containing Zn: 1.0 to 8.0 mass%, Fe: 0 85-1.5 mass%, Ni: 0.85-1.5 mass%, Si: 0.85-2.0 mass%, Cu: 0.2-0.5 mass%, and Ti: 0.01-0.05 mass % Of the brazing material at the natural potential of the sacrificial material, which is an aluminum alloy further comprising one or two or more of Al, and the balance being Al and inevitable impurities, and having a pH of 9 to 11 and a temperature of 80 to 100 ° C. An aluminum alloy clad material having a cathode current density of 20 μA / cm ² or less.   The aluminum alloy clad material according to claim 1, wherein the core material is a JIS3003 alloy, and the brazing material is any one of JISBA4343P, BA4045P, and BA4047P.

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