HIGH POTENTIAL AND HIGH CORROSION RESISTANCE ALUMINUM ALLOY AND HIGH CORROSION RESISTANCE HEAT EXCHANGER

A high-potential and high-corrosion resistance aluminum alloy and a high-corrosion resistance heat exchanger using the aluminum alloy are provided. The aluminum alloy includes: 0.6 to 0.8 percent by weight (wt %) of manganese (Mn); 0.05 to 0.30 wt % of magnesium (Mg); 0.05 to 0.35 wt % of zinc (Zn); 0.05 to 0.20 wt % of chromium (Cr); and a remaining wt % of aluminum (Al) and inevitable impurities, wherein a corrosion potential value of the aluminum alloy is in a range of −720 to −680 mV.

BACKGROUND

The disclosure relates to a high-potential and high-corrosion resistance aluminum alloy and a high-corrosion resistance heat exchanger using the aluminum alloy.

2. Description of Related Art

In general, a refrigerator includes a heat exchanger consisting of a cooling cycle in which a refrigerant starts from a compressor, sequentially passes through a condenser, a capillary pipe, an evaporator, and a suction pipe, and then returns to the compressor. The heat exchanger is an important component because it can determine the performance and lifespan of the refrigerator. In general, the evaporator is formed of an aluminum tube and fins, and aluminum alloy materials are widely used in consideration of price competitiveness and heat conduction.

In general, as the aluminum tube, 1000 series aluminum alloys with excellent extrudability and formability or 3000 series aluminum alloys with high strength and relatively superior corrosion resistance are used.

First, the 3000 series aluminum alloys, which have relatively superior corrosion resistance but poor processibility, are difficult to apply to aluminum tubes that go through several processing processes.

Accordingly, the 1000 series aluminum alloys with excellent extrudability and surface treatability have been mainly applied to conventional aluminum tubes. In general, while aluminum has high corrosion resistance by an oxide film formed thereon, potential difference corrosion may occur between a tube material and a fin material by influence of Si and Cu. In the case of using a 1000 series aluminum alloy, a tube may corrode first, leading to occurrence of pitting corrosion penetrating the tube. As a result, issues such as refrigerant leakage and cooling failure may occur due to pitting corrosion causing perforation of the tube.

As the most widely used method for preventing corrosion of aluminum to inhibit corrosion of the tube, a method of preventing corrosion of an evaporator by surface treatment (alumite) has been used. However, addition of the surface treatment may increase costs and coating defects may occur.

In addition, in order to prevent corrosion of the tube, a method of inducing sacrificial corrosion in a fin material may be used. However, there are limitations, for example, a 7000 series aluminum alloy including Mg and Zn or a non-universal material that lower potentials should be used as the fin material.

Because the suction pipe for supplying a refrigerant requires high corrosion resistance, a copper tube with excellent corrosion resistance has been generally used. However higher price of copper than that of aluminum alloys causes an increase in manufacturing costs, and thus attempts have been made to introduce aluminum alloys in terms of price competitiveness. However, sacrificial corrosion cannot be induced because the suction pipe is composed of a single material. Therefore, there is a need to develop an aluminum alloy having high corrosion resistance applicable to the suction pipe in order to reduce cost.

In the case of using an aluminum alloy for a heat exchanger pipe, because a trace amount of Mn is used therein to improve extrudability of the alloy, there are problems of insufficient corrosion resistance and strength for use as a material for heat exchanger tubes.

SUMMARY

Provided is an aluminum alloy which may have improved corrosion resistance and an increased corrosion potential value by designing the composition of the alloying elements.

Further, provided is a high-corrosion resistance heat exchanger causing uniform corrosion rather than pitting corrosion by inducing sacrificial corrosion of a fin by applying an aluminum alloy with improved corrosion resistance and an increased corrosion potential value to a tube of an evaporator of the heat exchanger.

Further still, provided is a heat exchanger which may have reduced costs by applying an aluminum alloy, which has enhanced corrosion resistance by replacing conventional copper (Cu), to a suction pipe.

According to an aspect of the disclosure, an aluminum alloy includes: 0.6 to 0.8 percent by weight (wt %) of manganese (Mn); 0.05 to 0.30 wt % of magnesium (Mg); 0.05 to 0.35 wt % of zinc (Zn); 0.05 to 0.20 wt % of chromium (Cr); and a remaining wt % of aluminum (Al) and impurities, wherein a corrosion potential value of the aluminum alloy is in a range of −720 to −680 mV.

A value of 53.2* [Mn]−8.44*[Mg]−131.9*[Zn]+0.01*[Cr] may be in a range of −12 to 32, where [Mn] is the wt % of Mg, [Mg] is the wt % Mg, [Zn] is the wt % of Zn, and [Cr] is wt % of Cr.

The value may be in a range of 16 to 30.

A sum of the wt % of Mn, the wt % of Mg, the wt % of Zn, and the wt % of Cr may be greater than 0 wt % and less than or equal to 1.6 wt %.

The aluminum alloy may further include at least one of 0.2 wt % or less of silicon (Si) and 0.25 wt % or less of iron (Fe).

The impurities may be 1.0 wt % or less.

According to an aspect of the disclosure, a heat exchanger includes a tube having an internal channel, wherein the tube is formed of an aluminum alloy including: 0.6 to 0.8 percent by weight (wt %) of manganese (Mn); 0.05 to 0.30% of magnesium (Mg); 0.05 to 0.35% of zinc (Zn); 0.05 to 0.20% of chromium (Cr); and a remaining balance of aluminum (Al) and impurities.

A value of) 53.2*[Mn]−8.44*[Mg]−131.9*[Zn]+0.01*[Cr] may be in a range of −12 to 32, where [Mn] is the wt % of Mg, [Mg] is the wt % Mg, [Zn] is the wt % of Zn, and [Cr] is wt % of Cr.

A sum of the wt % of Mn, the wt % of Mg, the wt % of Zn, and the wt % of Cr of the aluminum alloy may be greater than 0 wt % and less than or equal to 1.6 wt %.

The aluminum alloy may further include at least one of 0.2 wt % or less of silicon (Si) and 0.25 wt % or less of iron (Fe).

The impurities may be in an amount of 1.0 wt % or less.

A corrosion potential value of the tube may be −720 to −680 mV.

The tube includes a first tube, the heat exchanger further includes an evaporator including a plurality of fins coupled to an outer circumference surface of the first tube, and a corrosion potential value of the first tube may be higher than a corrosion potential value of each of the plurality of fins.

The corrosion potential value of each of the plurality of fins may be in a range of −840 to −700 mV.

A difference of the corrosion potential value of the first tube and the corrosion potential value of each of the plurality of fins may be in a range of 10 to 100 mV.

According to an aspect the present disclosure, provided is an aluminum alloy having excellent corrosion resistance and a high potential and having a novel composition of alloying elements may be provided.

According to another aspect of the present disclosure, provided is a heat exchanger with improved corrosion resistance may be provided by inducing uniform corrosion rather than pitting corrosion by inducing sacrificial corrosion of fins using the high-potential aluminum alloy according to the present disclosure as a tube material. In addition, costs may be reduced by using a general-purpose fin material in comparison with the use of a specialized fin material.

According to yet another aspect of the present disclosure, costs for coating may be reduced by realizing high corrosion resistance although a surface treatment process is omitted. In addition, because copper, which is commonly used in the environment that requires high corrosion resistance, is replaced, manufacturing costs of the heat exchanger may be reduced.

DETAILED DESCRIPTION

Various embodiments of the present disclosure and terms used herein are not intended to limit technical features disclosed herein to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes of the embodiments are encompassed in the present disclosure.

Regarding the description of the drawings, like reference numerals may be used for like or related elements throughout the drawings.

The singular form of a noun corresponding to an item may include one or more items unless the context states otherwise.

Throughout the specification, “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, and “at least one or A, B, or C” may each include any one or all possible combinations of A, B and C.

The term “and/or” is interpreted to include a combination or any of associated elements.

Throughout the specification, “in the range of X to Y,” “a number between X and Y,” “from X to Y,” and “up to X” may include beginning and end points X and Y.

Terms such as “first” or “second” are used to distinguish one component from other components and, therefore, the components are not limited by the terms in any other aspect (e.g., importance or order).

Also, the terms used throughout the specification ‘front’, ‘rear’, ‘top’, ‘bottom’, ‘side’, ‘left’, ‘right’, ‘upper’, ‘lower’, and the like are defined based on the drawings and the shape and position of each element are not limited by these terms.

The terms such as “including” or “having” are intended to indicate the existence of features, numbers, processes, operations, components, parts, or combinations thereof disclosed in the specification, and are not intended to preclude the possibility that one or more other features, numbers, processes, operations, components, parts, or combinations thereof may exist or may be added.

When an element is mentioned as being “connected to”, “coupled to”, “supported by”, or “contacting” another element, it includes not only a case that the elements are directly connected to, coupled to, supported by or contact each other but also a case that the elements are connected to, coupled to, supported by or contact each other through a third element.

When an element is mentioned as being located “on” another element, it implies not only that the element is in direct contact with the other element but also that a third element exists between the two elements.

Hereinafter, a high-potential and high-corrosion resistance aluminum alloy and a heat exchanger including a tube formed of the aluminum alloy according to various embodiments will be described in detail.

Aluminum Alloy

A high-potential and high-corrosion resistance aluminum alloy according to an embodiment may include, in percent by weight (wt %), 0.6 to 0.8% of manganese (Mn), 0.05 to 0.30% of magnesium (Mg), 0.05 to 0.35% of zinc (Zn), 0.05 to 0.20% of chromium (Cr), the remaining balance being aluminum (Al), and inevitable impurities.

A corrosion potential value of the high-potential and high-corrosion resistance aluminum alloy according to an embodiment may be −720 mV or more, preferably −720 to −680 mV, and more preferably −700 to −680 mV. These values are higher than corrosion potential values of 1000 series or 7000 series aluminum alloys that are commonly used in the art.

In addition, a corrosion rate of the high-potential and high-corrosion resistance aluminum alloy according to an embodiment, measured by the Copper Accelerated Acetic Acid Salt Spray (“CASS”) method, may be 25% or less, and preferably 23% or less. A lower corrosion rate indicates superior corrosion resistance.

Hereinafter, reasons for numerical limitations on the contents of alloying elements of the aluminum alloy according to an embodiment of the present disclosure will be described. Hereinafter, the unit is wt % unless otherwise stated.

Mn is an element increasing a potential of the aluminum alloy. In addition, Mn forms intermetallic compounds with Al and Mn, thereby reducing an Fe content in an Al matrix, and accordingly corrosion resistance of the aluminum alloy may be improved thereby. Therefore, Mn may be added in an amount of 0.6 wt % or more to increase the potential and corrosion resistance of the aluminum alloy. On the contrary, in the case where the Mn content exceeds 0.8 wt %, corrosion resistance may deteriorate.

Mg is an element lowering the potential of the aluminum alloy. However, Mg forms a fine Al8Mg5 phase with Al, thereby refining crystal grains and improving corrosion resistance. In addition, Mg is an effective element for improving mechanical strength of the aluminum alloy. Thus, with a too low Mg content, corrosion resistance and strength of the aluminum alloy may deteriorate. In consideration thereof, Mg may be added in an amount of 0.05 wt % or more. However, with an excess of Mg, the corrosion potential value of the aluminum alloy may decrease, and strength may increase resulting in reduction of extrudability. In consideration thereof, the upper limit of the Mg content may be controlled to 0.30 wt %.

Like Mg, Zn is an element lowering the potential of the aluminum alloy. In addition, Zn is an effective element for increasing resistance to pitting corrosion by inhibiting formation of Al3Mg2 by inducing formation of an AlMgZn phase. Pitting refers to corrosion that creates holes or pits on the surface of a metal due to local corrosion. Specifically, the AlMgZn phase may be formed as discontinuous precipitates at grain boundaries to prevent occurrence of corrosion in the grain boundaries so as to induce uniform corrosion. Because pitting corrosion may deteriorate durability of the heat exchanger, such corrosion should be minimized. In consideration thereof, Zn may be added in an amount more than 0.05 wt %. However, with an excess of Zn, the corrosion potential value of the aluminum alloy may decrease, and therefore the upper limit of the Zn content may be controlled to 0.35 wt %.

Cr is an essential element for improving corrosion resistance of the aluminum alloy. Cr serving as a grain refining element increases density of grain boundaries to form a passivated layer, thereby improving corrosion resistance. With a Cr content of less than 0.05 wt %, it is difficult to achieve the grain refining effect and additional improvement of strength in the aluminum alloy desired by adding Cr. However, a Cr content exceeding 0.20 wt % may rather worsen corrosion resistance.

A value of the high-corrosion resistance heat exchanger according to an embodiment calculated by Expression (1) below may satisfy the range of −12 to 32, and preferably the range of 16 to 30.

In the case where the value calculated by Expression (1) is low, the corrosion potential value of the aluminum alloy may also be low. In the case where the value calculated by Expression (1) is high, the corrosion potential value of the aluminum alloy may also be high. Therefore, in the case where the value calculated by Expression (1) satisfies the range of −12 to 32, the corrosion potential value desired by the present disclosure may be satisfied.

A sum of the Mn, Mg, Zn, and Cr contents of the high-potential and high-corrosion resistance aluminum alloy according to an embodiment may be more than 0 wt % but not more than 1.6 wt %. By controlling the sum of Mn, Mg, Zn, and Cr to 1.6 wt % or less, not only high corrosion resistance may be obtained by an oxide film formed on the surface, but also an appropriate level of yield strength may be maintained.

Aluminum (Al): The balance

The remaining component of the high-potential and high-corrosion resistance

aluminum alloy according to an embodiment is aluminum (Al). Al is a light element with high corrosion resistance due to an oxide film formed on the surface.

However, the composition may include unintended impurities inevitably incorporated from raw materials or surrounding environments, and thus addition of other alloy components is not excluded. These impurities are known to any person skilled in the art of manufacturing and details thereof are not specifically mentioned in the present disclosure.

The high-potential and high-corrosion resistance aluminum alloy according to an embodiment may further include at least one of silicon (Si) and iron (Fe) as inevitable impurities.

Si is a major impurity contained in industrial aluminum in the form of silica contained in bauxite that is a raw material ore of aluminum, serving as an element reducing corrosion resistance of an alloy by forming intermetallic compounds with Al and Cu. Therefore, in the present disclosure, Si is controlled as an impurity, and the upper limit thereof is adjusted to 0.2% or less.

Fe is a major impurity contained in industrial aluminum in the form of an iron oxide contained in bauxite that is a raw material ore of aluminum, serving as an element reducing corrosion resistance of an alloy by forming intermetallic compounds with Al and Cu. Therefore, in the present disclosure, Fe is controlled as an impurity, and the upper limit thereof is adjusted to 0.25% or less.

The high-potential and high-corrosion resistance aluminum alloy according to an embodiment may include the inevitable impurities in an amount of 1.0 wt % or less. In this regard, the inevitable impurities include Si and Fe. An impurity content exceeding 1.0 wt % in the aluminum alloy according to the present disclosure may indicate abnormal alloying such as excessive use of scrap or incorrect addition of a base alloy.

The high-potential and high-corrosion resistance aluminum alloy according to an embodiment may be manufacturing by melting an ingot having the above-described composition of alloying elements to obtain a molten metal, and casting the molten metal. In this regard, flux may be added to remove impurities and hydrogen gas from the molten metal during a melting process, but an excessive of the flux may deteriorate corrosion resistance of the aluminum alloy. Therefore, the amount of the flux may be controlled to 0.3 wt % or less of a total weight of the molten metal.

High-Corrosion Resistance Heat Exchanger

The high-corrosion resistance heat exchanger according to an embodiment may include a tube (pipe) having an internal channel in which the refrigerant flows. The tube may include a first tube 10 and a second tube 20.

The tube may be formed of an aluminum alloy including, by wt %, 0.6 to 0.8% of manganese (Mn), 0.05 to 0.30% of magnesium (Mg), 0.05 to 0.35% of zinc (Zn), 0.05 to 0.20% of chromium (Cr), the balance being aluminum (Al), and inevitable impurities. Reasons for numerical limitations on the contents of alloying elements of the aluminum alloy are as described above.

In addition, a value of the high-corrosion resistance heat exchanger according to an embodiment calculated by Expression (1) below may satisfy the range of −12 to 32, and preferably the range of 16 to 30. The reasons for numerical limitations in Expression (1) are as described above.

In the high-corrosion resistance heat exchanger according to an embodiment, a sum of the Mn, Mg, Zn, and Cr contents of the aluminum alloy may be more than 0 wt % but not more than 1.6 wt %. In addition, the aluminum alloy may further include at least one of silicon (Si) and iron (Fe), i.e., 0.2 wt % or less of Si and 0.25 wt % or less of Fe. In addition, the aluminum alloy may include 1.0 wt % or less of the inevitable impurities. The reasons for numerical limitations on the contents of alloying elements are as described above.

A corrosion potential value of the tube of the high-corrosion resistance heat exchanger according to an embodiment may be −700 mV or more, and preferably −720 to −680 mV. The high-potential and high-corrosion resistance aluminum alloy according to the present disclosure has a higher corrosion potential value than that of conventional general-purpose aluminum alloys for heat exchangers such as 1000 series and 7000 series aluminum alloys.

Hereinafter, the high-corrosion resistance heat exchangers according to various embodiments will be described with response to the accompanying drawings.

FIG. 1 is a diagram schematically illustrating the configuration of a heat exchanger according to an embodiment of the present disclosure and a cooling cycle in accordance therewith.

Referring to FIG. 1, a heat exchanger of a refrigerator includes a compressor 3 configured to compress a refrigerant at a high temperature and a high pressure, a condenser 4 configured to condense the refrigerant flowing from the compressor 3 into a liquid phase, a capillary pipe 21 configured to expand the refrigerant flowing from the condenser 4, an evaporator 1 configured to generate cold air by evaporating the refrigerant flowing from the capillary pipe 21, and a suction pipe 2 configured to guide the refrigerant discharged from the evaporator 1. In addition, hot pipes 6 and cluster pipes 5 may be evenly arranged on the front and both sides of the main body of the refrigerator between the condenser 4 and the capillary pipe 21 to further dissipate heat, which was not sufficiently dissipated through the condenser 4, from the refrigerant, and to prevent condensation on the front and both sides of the main body of the refrigerator by heating.

FIG. 2 illustrates an evaporator 1 in the high-corrosion resistance heat exchanger according to an embodiment of the present disclosure.

In the high-corrosion resistance heat exchanger according to an embodiment of the present disclosure, the evaporator 1 serves to evaporate the refrigerant flowing from the capillary pipe 21 to generate cold air.

Referring to FIG. 2, a high-corrosion resistance heat exchanger according to an embodiment may include a first tube 10 having an internal channel in which the refrigerant flows, and a fin 11 coupled to the outer circumference surface of the first tube 10. The fin 11 may be provided in plural.

In addition, the first tube 10 may be arranged in a zigzag form with multiple rows to enlarge the heat exchange area between the refrigerant flowing in the first tube 10 and external air.

In addition, the plurality of fins 11 may be arranged between the plurality of rows of the first tube 10 for efficient heat exchange between the refrigerant flowing in the channel formed inside the first tube 10 and the external air. That is, the fins 11 may be arranged in contact with the first tube 10 in a space for heat exchange. In addition, the plurality of fins 11 may be arranged along the outer circumference surface of the first tube 10 in the lengthwise direction of the first tube 10. In this regard, the shape of the fin 11 is not particularly limited. In addition, the plurality of fins 11 may be installed at regular intervals to prevent corrosion of the fins 11, but installation positions are not particularly limited.

The plurality of fins 11 may be coupled to the first tube 10 by a press-fit method. That is, the first tube 10 and the fin 11 may be coupled to each other by pushing the fin 11 with a hole smaller than an outer diameter of the first tube 10 into the first tube 10.

In the heat exchanger according to an embodiment, uniform corrosion, rather than pitting corrosion, may occur in the first tube 10 and the fin 11 by applying the aluminum alloy having the above-described alloy composition and content ranges of the elements to the first tube 10 of the evaporator 1. Therefore, the heat exchanger with improved corrosion resistance may be provided in the present disclosure.

A corrosion potential value of the first tube 10 may be greater than a corrosion potential value of the fin 11. For example, the corrosion potential value of the first tube 10 may be higher than a corrosion potential value of the fin 11 by 10 mV or more. Therefore, sacrificial corrosion of the fin 11 is induced to protect the first tube 10 from corrosion. The sacrificial corrosion refers to a process of inducing corrosion of one metal to prevent corrosion of another metal. This may occur due to a potential difference between different metals. In this case, the corrosion of the metal with a lower potential is accelerated, while the metal with a higher potential may be protected from corrosion.

In an embodiment, corrosion of the fin 11 having the lower potential may be accelerated and the first tube 10 having the higher potential may be protected from corrosion. Particularly, it is characterized in that the aluminum alloy, used for a tube of conventional heat exchangers, is used to form the fin 11, and the novel aluminum alloy for the first tube 10 is designed to obtain high corrosion resistance and high potential to induce sacrificial corrosion of the fin 11. Therefore, corrosion resistance may further be improved by inducing the sacrificial corrosion of the fin 11 not only by increasing corrosion resistance of the first tube 10 by using the novel alloy composition, but also by combining the high-potential first tube 10 and the fin 11.

In an embodiment, the corrosion potential value of the first tube 10 may be −720 mV or more, preferably −720 to −680 mV, and more preferably −700 to −680 mV. Also, the corrosion potential value of the fin 11 may be −700 mV or less, preferably −840 to −700 mV, and more preferably −840 to −715 mV. In this regard, a difference of the corrosion potential value between the first tube 10 and the fin 11 may be 10 mV or more, and preferably 10 to 100 mV.

In an embodiment, the fin 11 may be formed of a 1000 series aluminum alloy or 7000 series aluminum alloy used as a material of tubes for conventional heat exchangers. 1000 series aluminum alloys commonly used in heat exchangers theoretically have a corrosion potential value of −720 to −700 mV. Examples of the 1000 series aluminum alloys may include Al 1050 having a corrosion potential value of about −720 mV, Al 1070 having a corrosion potential value of about−715 mV, and Al 1100 having a corrosion potential value of about −710 mV. Therefore, preferably, Al 1050 or Al 1070 with relatively lower corrosion potential values may be used for the fin 11, and more preferably, Al 1050 may be used therefor.

Meanwhile, 7000 series aluminum alloys with high strength and excellent workability theoretically have a low corrosion potential value of −840 to −800 mV due to a relatively high Zn content. Examples of the 7000 series aluminum alloys may include Al 7072 having a corrosion potential value of about −820 mV, but are not limited thereto.

In an embodiment, the fin 11 may be formed of an aluminum alloy including, in percent by weight (wt %), 1.0% or less of Si, 1.0% or less of Fe, 0.20% of less of Cu, 0.05% or less of Mn, 0.5% or less of Mg, 1.5% or less of Zn, 0.03% or less of Ti, and the balance being Al and other inevitable impurities.

Although the aluminum alloy according to the present disclosure has excellent corrosion resistance in itself, the corrosion potential value thereof is higher than that of conventional general-purpose aluminum alloys such as 1000 series or 7000 series aluminum alloys, so that superior corrosion resistance may be obtained by inducing sacrificial corrosion of the fin 11.

The high-corrosion resistance heat exchanger according to an embodiment may further include plate-type evaporators 12 arranged on both of the first tube 10 in the height-wise direction. The plate-type evaporator 12 not only performs heat exchange function, but also fixes the first tube 10 so as to maintain the shape of the evaporator 1. In addition, subsidiary components such as a sensor may be coupled to the plate-type evaporator 12.

Suction Pipe

FIG. 3 illustrates a suction pipe 2 of a high-corrosion resistance heat exchanger according to an embodiment.

In the high-corrosion resistance heat exchanger according to an embodiment, the suction pipe 2 transfers the refrigerant discharged from the evaporator 1 to the compressor 3.

Referring to FIGS. 1 and 3, the high-corrosion resistance heat exchanger according to an embodiment may include the suction pipe 2 including the second tube 20 having an internal channel in which the refrigerant flows. The capillary pipe 21 may be provided in plural.

In addition, the capillary pipes 21 may be attached to the suction pipe 2. For example, the capillary pipes 21 may be attached to the outer circumference surface of the suction pipe 2 or inserted into the suction pipe 2, but the position and shape thereof are not particularly limited.

In the high-corrosion resistance heat exchanger according to an embodiment, the capillary pipes 21 serve to expand the refrigerant flowing from the condenser 4 and then supply the refrigerant into the evaporator 1.

By applying the aluminum alloy having the above-described composition and content ranges of the elements to the suction pipe 2, excellent corrosion resistance may be obtained without inducing sacrificial corrosion.

The high-potential and high-corrosion resistance aluminum alloy according to an embodiment includes, in percent by weight (wt %), 0.6 to 0.8% of manganese (Mn), 0.05 to 0.30% of magnesium (Mg), 0.05 to 0.35% of zinc (Zn), 0.05 to 0.20% of chromium (Cr), the balance being aluminum (Al), and inevitable impurities. The high-potential and high-corrosion resistance aluminum alloy may have a corrosion potential value of about −720 to −680 mV.

The high-potential and high-corrosion resistance aluminum alloy may have a value of Expression (1) satisfying the range of −12 to 32.

The high-potential and high-corrosion resistance aluminum alloy may have a value of Expression (1) satisfying the range of 16 to 30.

A sum of the Mn, Mg, Zn, and Cr contents in the high-potential and high-corrosion resistance aluminum alloy may be more than 0 wt % but not more than 1.6 wt %.

The high-potential and high-corrosion resistance aluminum alloy may further include at least one of 0.2% or less of silicon (Si) and 0.25% or less of iron (Fe).

The high-potential and high-corrosion resistance aluminum alloy may include 1.0 wt % or less of the inevitable impurities.

The high-corrosion resistance heat exchanger according to an embodiment includes a tube having an internal channel in which a refrigerant flows. The tube may be formed of an aluminum alloy including, in percent by weight (wt %) 0.6 to 0.8% of manganese (Mn), 0.05 to 0.30% of magnesium (Mg), 0.05 to 0.35% of zinc (Zn), 0.05 to 0.20% of chromium (Cr), the balance being aluminum (Al), and inevitable impurities.

The aluminum alloy may have a value of Expression (1) satisfying the range of −12 to 32.

A sum of the Mn, Mg, Zn, and Cr contents in the aluminum alloy may be more than 0 wt % but not more than 1.6 wt %.

The aluminum alloy may further include at least one of 0.2% or less of silicon (Si) and 0.25% or less of iron (Fe).

The aluminum alloy may include 1.0 wt % or less of the inevitable impurities.

The tube may have a corrosion potential value of −720 to −680 mV.

The tube may include a first tube, and the high-corrosion resistance heat exchanger may include an evaporator including a plurality of fins coupled to the outer circumference surface of the first tube. The corrosion potential value of the first tube may be higher than the corrosion potential value of the fin.

The corrosion potential value of the fin may be from −840 to −700 mV.

A difference of the corrosion potential value between the first tube and the fin may be 10 to 100 mV.

The first tube may be arranged in a zigzag form with multiple rows.

The plurality of fins may be arranged along the outer circumference surface of the first tube in the lengthwise direction of the first tube.

Plate-type evaporators may further be arranged on both sides of the first tube in the height-wise direction.

The plurality of fins may be coupled to the first tube by a press-fit method.

The tube may include a second tube, and the high-corrosion resistance heat exchanger may include a suction pipe consisting of the second tube; and a plurality of capillary pipes attached to the suction pipe.

Hereinafter, the present disclosure will be described in more detail with reference to the following examples. However, the following examples are merely presented to exemplify the present disclosure, and the scope of the present disclosure is not limited thereto.

EXAMPLES

After manufacturing aluminum alloys having the compositions shown in Table 1 below, theoretical corrosion potential values thereof were calculated, and the CASS test was performed to evaluate corrosion resistance of the aluminum alloys.

In addition, values of the compositions of alloying elements shown in Table 1 below calculated by Expression (1) are shown.

The theoretical corrosion potential values were calculated based on “ASM Metal handbook, volume 13B, corrosion materials”.

The CASS test was performed for 50 days by repeating a cycle consisting of spraying a mixture of 1% NaCl and 1 g of copper chloride dihydrate per 3.8 L of the salt solution to a specimen at a rate of 1.5±0.5 mL/hr every 24 hours at a temperature of 49° C. at a pH level of 2.8 to 3.0.

Type
Mn
Mg
Zn
Cr
(1)
(mV)
rate (%)

Referring to Table 1, it was confirmed that the aluminum alloys of Examples 1-1 to 1-4 satisfying the composition of alloying elements according to the present disclosure had a corrosion potential value satisfying the range of −720 to −680 mV and a corrosion rate of 23% or less indicating superior corrosion resistance. On the contrary, the aluminum alloys of Comparative Examples 1-1 to 1-3 out of the composition of alloying elements according to the present disclosure had a corrosion potential value not more than −720 mV or a corrosion rate exceeding 25% indicating inferior corrosion resistance. Particularly, in Comparative Examples 1-2 and 1-3 failing to satisfy the value of Expression (1) of −12 to 32, low corrosion potential values not more than −725 mV were obtained.

In addition, after constituting evaporators as shown in Table 2 below, the Sea Water Acetic Acid Test (SWAAT) was performed to evaluate corrosion resistance on the basis of tube/fin combinations.

Comparative
Example
Example
Example

Tube
Type of Al
Al 1070
Example
Example
Example

alloy

Fin
Type of Al
Al 1100
Al 1100
Al 1050
Al 7072

alloy

The SWAAT was performed for 14 days by repeating a cycle consisting of spraying a mixture of 5% NaCl and acetic acid to a specimen at a rate of 1.5±0.5 mL/hr every 24 hours at a temperature of 49° C. at a pH level of 2.8 to 3.0. FIGS. 4A to 4D are photographs of tubes according to Comparative Example 2 and Examples 2-1 to 2-3 after the SWAAT.

Referring to FIG. 4A, in the case of Comparative Example 2 in which a conventional aluminum alloy Al 1070 was used as the tube material, the corrosion potential value of the tube material was lower than that of the fin material Al1100, so that sacrificial corrosion of the tube occurred by reverse potential.

On the contrary, the aluminum alloy of Example 1-1 prepared according to Table 1 was used in Examples 2-1 to 2-3, and the corrosion potential value of the aluminum alloy of Example 1-1 was −690 mV. Because the corrosion potential value of the tube material was higher than that of the fin material, sacrificial corrosion of the fin material occurred, so that the tube was protected. Furthermore, referring to FIGS. 4B to 4D, it was confirmed that corrosion of the tube decreased as the difference of corrosion potentials between the tube and the fin increased.

That is, by introducing the aluminum alloy according to the present disclosure having a high corrosion potential value into the tube, sacrificial corrosion of the fin may be induced, and accordingly it was confirmed that a heat exchanger with excellent corrosion resistance may be manufactured. In addition, because the aluminum alloy according to the present disclosure has excellent corrosion resistance while having a relatively high corrosion potential value, the aluminum alloy may also be applied to a suction pipe independently provided without a component inducing sacrificial corrosion in the heat exchanger.

According to one or more embodiments of the present disclosure, an aluminum alloy having excellent corrosion resistance and a high potential and having a novel composition of alloying elements may be provided.

According to one or more embodiments of the present disclosure, a heat exchanger with improved corrosion resistance may be provided by inducing uniform corrosion rather than pitting corrosion by inducing sacrificial corrosion of fins using the high-potential aluminum alloy according to the present disclosure as a tube material. In addition, costs may be reduced by using a general-purpose fin material in comparison with the use of a specialized fin material.

According to one or more embodiments of the present disclosure, costs for coating may be reduced by realizing high corrosion resistance although a surface treatment process is omitted. In addition, because copper, which is commonly used in the environment that requires high corrosion resistance, is replaced, manufacturing costs of the heat exchanger may be reduced.

While various embodiments have been described above with reference to the drawings, the present disclosure is not limited thereto, and any combination or substitution of components as appropriate is included within the scope of the present disclosure. In some embodiments, modifications such as combinations, changes in the order of processes, and various changes in design may be made on the basis of knowledge of a person skilled in the art, and such modified embodiments are within the scope of the present disclosure and the appended claims.