ALUMINUM ALLOY

Abstract

The present disclosure relates to an aluminum alloy having chloride resistance and corrosion resistance against harmful gas environments as well as processability to the extent of undergoing extrusion and drawing. The aluminum alloy according to the present disclosure comprise 0.1-4.5 wt % of Mg, 0.1-0.60 wt % of Zn, 0.05-0.1 wt % of Fe, 0.05-0.1 wt % of Si, and the balance Al.

Description

TECHNICAL FIELD

The disclosure relates to an aluminum alloy. More particularly, the disclosure relates to an aluminum alloy having superior corrosion resistance as well as having processability to an extent of undergoing extrusion and drawing.

BACKGROUND ART

Aluminum on its own not only has superior characteristics such as processability, being lightweight, and conductivity, but also has the characteristic of easily alloying with other metals. Accordingly, aluminum alloy may include various material properties according to the components of the alloying element and thus, is widely used in various fields of industry.

However, despite there already being aluminum alloys with various properties, due to technological advances continuously being upgraded and diversified, there is an ongoing need for development of aluminum alloy with strict properties required in a variety of technical fields.

In particular, recently there is a growing need for development of an aluminum alloy having chloride resistance and corrosion resistance against harmful gas environments as well as having processability to an extent of undergoing extrusion and drawing.

DISCLOSURE

Technical Problem

Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide an aluminum alloy having chloride resistance and corrosion resistance against harmful gas environments as well as having processability to an extent of undergoing extrusion and drawing.

Technical Solution

According to an embodiment of the disclosure, an aluminum alloy includes 0.1 to 0.45 wt % of Mg, 0.1 to 0.60 wt % of Zn, 0.05 to 0.1 wt % of Fe, 0.05 to 0.1 wt % of Si, and a balance Al.

Here, the Mg may be 0.15 to 0.35 wt %.

Meanwhile, the Zn may be 0.3 to 0.55 wt %.

Meanwhile, a total of wt % of the Mg, the Zn, the Fe and the Si may not exceed 1.0 wt %.

Meanwhile, at least one of a Mg₃₂(Al, Zn)₄₉ phase and a Al₃Mg₂ phase may be formed by the Mg and the Zn.

Here, a fraction of the Mg₃₂(Al, Zn)₄₉ phase may not exceed 0.05%.

Meanwhile, a fraction of the Al₃Mg₂ phase may not exceed 0.02%.

DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B, which relate to related art, are views illustrating a composition table representing a composition range of aluminum alloys of 1000 series and 7000 series, respectively;

FIG. 2A is a view illustrating a composition table for representing a composition range of aluminum alloy according to the disclosure;

FIG. 2B is a view illustrating a composition table representing a fraction of a compound formed according to a Mg and Zn content according to the disclosure;

FIG. 3 is a view illustrating a result of an electrochemical test for proving an effect according to the disclosure;

FIGS. 4A to 5C are views illustrating a result of a half-immersion test for proving an effect according to the disclosure;

FIGS. 6A to 7C are views illustrating a result of a CASS test for proving an effect according to the disclosure; and

FIG. 8 is a view illustrating a result of a CASS test and a SWAAT test according to various composition ranges of the disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The embodiments of the disclosure may be applied with various modifications and may include various embodiments. Accordingly, specific embodiments may be illustrated in the drawings and descriptions may be provided in detail in the detailed description. However, it should be noted that the various embodiments are not for limiting the scope of the disclosure to a specific embodiment, but they should be interpreted to include various modifications, equivalents and/or alternatives of the embodiments disclosed herein. In describing the embodiments, like reference numerals may be used for like elements.

In case it is determined that in describing embodiments, detailed description of related known technologies may unnecessarily confuse the gist of the disclosure, the detailed description may be omitted.

In addition thereto, the embodiments below may be modified to various forms, and the technical scope of disclosure is not limited to the embodiments described below. Rather, the embodiments more faithfully complete the disclosure, and are provided to fully convey the technical idea of the disclosure to a person of ordinary skill in the art.

The terms used herein are used merely to describe a specific embodiment, and is not intended to limit the scope of protection. A singular expression may include a plural expression, unless otherwise specified.

Expressions such as, for example, and without limitation, “comprise,” “may comprises,” “include,” “may include,” or the like used herein may designate a presence of a corresponding characteristic (e.g., elements such as a number, a function, an operation or a component), and not preclude a presence of additional characteristics.

In the disclosure, expressions such as “A or B,” “at least one of A and/or B,” or “one or more of A and/or B” may include all possible combinations of the items listed together. For example, “A or B,” “at least one of A and B,” or “at least one of A or B” may refer to all cases including (1) at least one of A, (2) at least one of B, or (3) both of at least one of A and at least one of B.

Meanwhile, various elements and areas in the drawings have been schematically illustrated. Accordingly, the technical idea of the disclosure is not limited by the relative size or distance illustrated in the accompanied drawings.

The embodiments will be described in greater detail below with reference to the accompanying drawings to assist those of ordinary skill in the art to easily understand the disclosure.

FIGS. 1A and 1B, which relate to related art, are views illustrating a composition table representing a composition range of aluminum alloys of a 1000 series and a 7000 series, respectively.

In general, aluminum (Al) is widely used overall in the industry for its lightweight, easy to cast, easy to alloy with other metals, and good electricity and heat conductivity. In particular, recently aluminum alloy in which aluminum is mixed with other metals are widely being used to improve fuel economy or reduce weight of automobiles and electronic appliances.

Aluminum alloy may be classified into various types according to the components of the alloying element. There may be various methods to the classification method, but aluminum alloy in particular may be classified to aluminum alloys of 1000 series to 9000 series according to JIS industrial standard. Further, the aluminum alloy may show various material properties according to the type thereof.

For example, as illustrated in FIG. 1A, the 1000 series aluminum alloy may be referred to as a so-called pure aluminum for industrial use as an alloy with 99.0% aluminum purity while including elements such as silicon (Si), iron (Fe), magnesium (Mg) and zinc (Zn). In the case of the 1000 series alloy, characteristics such as superior light reflectability and heat conductivity, good corrosion resistance despite low strength, and easy weldability and processability are exhibited.

Meanwhile, as illustrated in FIG. 1B, the 7000 series aluminum alloy is a heat processed alloy with Zn and Mg as main additive components. In particular, the 7000 series alloy may have a high-strength characteristic by a deposition phenomenon according to heat processing and curing. In the case of the 7000 series alloy, various elements such as manganese (Mn), chromium (Cr) and zirconium (Zr) in addition to Zn and Mg may be added for various mechanical properties, but the processability and corrosion resistance may reduce according to the adding of the elements in general.

Meanwhile, although not illustrated, in the case of a 3000 series alloy which is a non-heat treated alloy with Mn as a main additive component, the alloy exhibits a slightly higher strength compared to the 1000 series alloy, and a superior moldabilty and corrosion resistance.

As described above, because the aluminum alloy exhibits various characteristics according to the alloying elements included therein and a ratio of the alloying elements, in order to obtain an aluminum alloy appropriate to a use purpose, alloying elements appropriate therefor and the ratio thereof need to be selected.

In particular, generally the 1000 series alloy and the 3000 series alloy having high processability are used as aluminum alloy for extrusion and drawing.

Further, because passive metals such as aluminum have a superior corrosion resistance by forming a dense Al₂O₃ oxide film on the surface, it may be stably used in neutral environments. Accordingly, the 1000 series alloy having aluminum purity of 99.0% or more and the 3000 series alloy, which is an alloy for improving strength within a parameter of not significantly reducing the moldability and corrosion resistance of the 1000 series, exhibit superior corrosion resistance in general.

However, even in the case of the 1000 series alloy and the 3000 series alloy according to the related art, concerns over limitations in chloride resistance and corrosion resistance in use environments where much moisture is generated may be observed.

Specifically, in the case of the 1000 series alloy and the 3000 series alloy according to the related art, a local corrosion in a pitting form, that is a pitting corrosion, may be generated on a surface of a tube in a use environment in which much moisture may be generated. In addition thereto, a micro galvanic corrosion may be generated in a grain boundary with respect to high potential metal elements such as Fe, and copper (Cu) from among alloying elements.

Accordingly, when using the 1000 series alloy and the 3000 series alloy of the related art in a chloride resistant and harmful gas environment, treating the surface of an aluminum tube with special coating to improve corrosion resistance may be unavoidable, and thus lead to an increase in manufacturing cost and a decrease in efficiency of the manufacturing process.

An aspect of the disclosure is to solve the above-described disadvantages, and relates to an aluminum alloy having chloride resistance and corrosion resistance against harmful gas environments as well as processability to the extent of undergoing extrusion and drawing.

FIG. 2A is a view illustrating a composition table for representing a composition range of aluminum alloy according to the disclosure, and FIG. 2B is a view illustrating a composition table representing a fraction of a compound formed according to a Mg and Zn content according to the disclosure.

As illustrated in FIG. 2A, the aluminum alloy according to the disclosure may include 0.1 to 0.45 wt % of Mg, 0.1 to 0.60 wt % of Zn, 0.05 to 0.1 wt % of Fe, 0.05 to 0.1 wt % of Si, and the balance Al.

In particular, the aluminum alloy according to the disclosure has superior corrosion resistance because it includes 0.1 to 0.45 wt % of Mg and 0.1 to 0.60 wt % of Zn.

Specifically, if the wt % of Mg is less than 0.1 or if the wt % of Zn is less than 0.1, obtaining corrosion resistance to the extent the disclosure aims to achieve may be difficult. Alternatively, if the wt % of Mg exceeds 0.45 or if the wt % of Zn exceeds 0.60, the strength may increase and it may be difficult to secure a processability to the extent of undergoing extrusion and drawing.

Meanwhile, with respect to the aluminum alloy according to the disclosure, it may be more preferable if the Mg is 0.15 to 0.35 wt %. Further, with respect to the aluminum alloy according to the disclosure, it may be more preferable if the Zn s 0.3 to 0.55 wt %. That is, if the Mg is 0.15 to 0.35 wt % and the Zn is 0.3 to 0.55 wt %, the effect of corrosion resistance according to the disclosure may be more remarkably exhibited, while concurrently securing processability to the extent of undergoing extrusion and drawing.

If Si and Fe are included by a specific wt % or more in the aluminum alloy according to the disclosure, because the corrosion resistance may be weakened and pitting may be increased accordingly, it may be preferable for the wt % of Fe to be 0.05 to 0.1, and the wt % of Si to be 0.05 to 0.1 in the disclosure.

Meanwhile, with respect to the aluminum alloy according to the disclosure, it may be preferable for the total wt % of Mg, Zn, Fe and Si to not exceed 1.0 wt %. In other words, it may be preferable for the wt % of Al to be 99.0%. That is, because the aluminum alloy according to the disclosure aims to secure a high corrosion resistance while having a processability to the extent of undergoing extrusion and drawing, it may be preferable for the aluminum to have a purity of 99.0% or more.

Meanwhile, the aluminum alloy according to the disclosure may be included with unavoidable impurities in the alloying process other than the alloying element as described above or the manufacturing process of the aluminum tube. However, in the disclosure, it may be preferable for the impurities other than the Al, Mg, Zn, Fe and Si as described above to not exceed 1.0%.

In particular, to achieve the object of the disclosure, the adding of impurities which may influence the corrosion resistance and the processability of aluminum alloy is to be excluded, and even when impurities are unavoidably added, the added content is to be minimized.

For example, it may be preferable for the aluminum alloy according to the disclosure to not include Mn, Cr, Zr, and the like. That is, when elements such as Mn, Cr, and Zn are included, the mechanical characteristics such as strength may be improved, but alternatively, securing processability to the extent of undergoing extrusion and drawing may be difficult.

The improvement of corrosion resistance of aluminum alloy according to the disclosure will be described in detail below.

How the corrosion resistance of the aluminum alloy varies according to the type of the alloying element and the composition range may be self-evidently grasped by those of ordinary skill in the art. For example, the Zn included in the aluminum alloy according to the disclosure may inhibit a solid solution of Mg on the Al matrix, and accordingly the corrosion resistance of aluminum alloy may be improved.

Meanwhile, the property of alloy may be influenced by not only its composition, but also the state of the microstructure included in the alloy. Accordingly, in describing the corrosion resistance of the aluminum alloy according to the disclosure, a phase of the compound formed according to the Mg and Zn may be considered.

Specifically, the phase of the compound in the aluminum alloy may be formed according to the Mg and Zn included in the aluminum alloy according to the disclosure, and a fraction of the compound phase formed according to the wt % of Mg and Zn included in the alloy may be varied.

As illustrated in FIG. 2B, the aluminum alloy according to the disclosure may be formed with at least one from among a Mg₃₂(Al, Zn)₄₉ phase and a Al₃Mg₂ phase. Further, the pitting corrosion of the aluminum alloy may be reduced by at least one from among the formed Mg₃₂(Al, Zn)₄₉ phase and Al₃Mg₂ phase. In other words, the corrosion resistance of the aluminum alloy may be improved by at least one from among the formed Mg₃₂(Al, Zn)₄₉ phase and Al₃Mg₂ phase.

Specifically, the formed Mg₃₂(Al, Zn)₄₉ phase and Al₃Mg₂ phase may reduce the potential difference with the Al matrix in the grain boundary to reduce surface pitting. In particular, if the fraction of the Mg₃₂(Al, Zn)₄₉ phase and Al₃Mg₂ phase become such that continuous distribution in the grain boundary is possible, the effect in corrosion resistance may become more significant.

A primary fraction according to the wt % of Mg and Zn of aluminum alloy according to the disclosure and a fraction of the Mg₃₂(Al, Zn)₄₉ phase and Al₃Mg₂ phase may be obtained as illustrated in FIG. 2B.

For example, as illustrated in FIG. 2B, if the wt % of Mg is 0.30 and the wt % of Zn is 0.50 with respect to the aluminum alloy according to the disclosure, the fraction of the Mg₃₂(Al, Zn)₄₉ phase may be 0.21% and the fraction of the Al₃Mg₂ phase may be 0.003, accordingly. In this case, having an effect in significantly improving corrosion resistance may be demonstrated through test results as described below.

Meanwhile, it may be preferable for the fraction of the Mg₃₂(Al, Zn)₄₉ phase by the Mg, Zn, and Al to not exceed 0.05%. Further, in the case of aluminum alloy according to the disclosure, it may be preferable for the fraction of the Al₃Mg₂ phase in the Al and Mg to not exceed 0.02%.

That is, if the fraction of the Mg₃₂(Al, Zn)₄₉ phase exceeds 0.05% or if the fraction of the Al₃Mg₂ phase exceeds 0.02%, it may be difficult to secure the processability to the extent of the undergoing extrusion and drawing.

For example, if the wt % of Mg is 0.50 and the wt % of Zn is 0.50 with respect to the aluminum alloy, and the fraction of the Mg₃₂(Al, Zn)₄₉ phase is 0.070% and the fraction of the Al₃Mg₂ phase is 0.028 according thereto, because securing the processability to the extent of undergoing extrusion and drawing may be difficult due to the strength of the material increasing, it may not be included in the composition range of the alloying element according to the disclosure.

Meanwhile, even if the aluminum alloy according to the disclosure undergoes the process of extrusion and drawing for the manufacturing of the aluminum tube, the corrosion resistance as described above may not be reduced. This will be demonstrated through use of the aluminum tube used as a sample in various tests as described below.

According to the various embodiments of the disclosure as described above, an aluminum alloy having chloride resistance and corrosion resistance against harmful gas environment as well as processability to the extent of undergoing extrusion and drawing may be provided.

According thereto, leaks and water leakage by the corrosion of the aluminum alloy may be prevented, and by using the aluminum alloy according to the disclosure rather than using the copper for the securing of corrosion resistance, costs may be reduced.

The significant effect in improvement of corrosion resistance as described above may be demonstrated according to test results which will be described below. That is, through various test results which may assess the corrosion resistance of the aluminum alloy, the effect in improvement of corrosion resistance according to the disclosure will be described.

FIG. 3 is a view illustrating a result of an electrochemical test for proving an effect according to the disclosure.

In order to demonstrate the effect in improvement of corrosion resistance according to the disclosure, Electrochemical Impedance Spectroscopy was conducted. Here, the Electrochemical Impedance Spectroscopy may refer to a method of measuring impedance by using a weak alternating signal having different frequency.

The test was conducted with respect to the aluminum alloy (hereinbelow, 0.3 Mg sample) including 0.31 wt % of Mg, 0.5 wt % of Zn, 0.08 wt % of Si and 0.09 wt % of Fe which is an embodiment according to the disclosure in a 5% sodium chloride (NaCl) environment.

In addition, the test was conducted with respect to a comparison group of an aluminum alloy (hereinafter, Al1070 sample) including 0.115 wt % of Si, 0.094 wt % of Fe, 0.0053 wt % of Cu, 0.004 wt % of Mn and 0.004 wt % of Ti, an aluminum alloy (hereinafter, 0.15Zr sample) including 0.1 wt % of Si, 0.09 wt % of Fe and 0.16 wt % of Zr, and an aluminum alloy (hereinafter, 0.6Mg sample) including 0.084 wt % of Si, 0.11 wt % of Fe, 0.61 wt % of Mg and 0.25 wt % of Zn.

When impedance is measured through Electrochemical Impedance Spectroscopy, changes in electrochemical properties may be analyzed through a Nyquist plotting method which illustrates a Zre (real resistance, real part) at an x-axis and a Zim (imaginary reactance, imaginary part) at a y-axis as illustrated in FIG. 3.

Then, the corrosion resistance of the sample may be analyzed through changes in the assessed electrochemical property. Specifically, with respect to graphs 310, 320, 330 and 340 as in FIG. 3, the corrosion resistance of the sample may be interpreted as great the greater the size of the semicircle.

Referring to FIG. 3, the size of the semicircle may appear the smallest in the case of the graph 310 with respect to the Al1070 sample, and the size of the semicircle may appear second smallest following the graph with respect to the Al1070 sample in the case of the graph 330 with respect to the 0.15Zr sample. That is, in the case of the Al1070 sample and the 0.15Zr sample, the samples having a relatively low corrosion resistance compared to other samples may be confirmed.

Because the size of the semicircle appears relatively large in the case of the graph 320 with respect to the 0.6Mg sample, it can be known that the sample has a relatively high corrosion resistance compared to the Al1070 sample and the 0.15Zr sample. In addition, and in the case of the graph 340 with respect to the 0.3Mg sample, the samples having the highest corrosion resistance from among all samples may be confirmed because the size of the semicircle appears to be the greatest.

Based on analyzing the graph representing the result according to the test, in the case of the 0.3Mg sample according to the disclosure, that is in the case of the aluminum alloy including 0.31 wt % of Mg, 0.5 wt % of Zn, 0.08 wt % of Si, and 0.09 wt % of Fe, the sample having a high corrosion resistance compared to the comparison group may be confirmed.

Meanwhile, even the 0.6Mg sample may have a corrosion resistance similar to that of the 0.3Mg sample, but as described above, if the wt % of Mg included in the aluminum alloy exceeds 0.45, the strength may increase and because securing processability to the extent of undergoing extrusion and drawing may be difficult, it is not included in the composition range according to the disclosure.

Meanwhile, electrochemical physical quantities such as current density may be measured through various electrochemical methods such as Electrochemical Impedance Spectroscopy as described above, and a corrosion rate may be calculated based on the measured electrochemical physical quantities.

Referring to FIG. 3, the corrosion rates of the Al1070 sample, the 0.15Zr sample, and the 0.3Mg sample calculated based on a CASS test conducted under conditions described below may be confirmed. Specifically, as illustrated in FIG. 3, the corrosion rates of 1.46 mm/y in the case of the Al1070 sample, 0.93 mm/y in the case of the 0.15Zr sample, and 0.62 mm/y in the case of the 0.3Mg sample have been calculated.

Referring to FIG. 5C, the same six movement information of the camera are represented to be different shake information according to viewing areas (front area and the back area in FIG. 5C) of the user.

That is, taking into reference the calculated corrosion rate, like the result having analyzed the graphs 310, 320, 330 and 340 with respect to the sample, in the case of the 0.3Mg sample according to the disclosure, that is in the case of the aluminum alloy including 0.31 wt % of Mg, 0.5 wt % of Zn, 0.08 wt % of Si, and 0.09 wt % of Fe, it may be confirmed that the sample has a high corrosion resistance compared to the comparison group.

FIGS. 4A to 5C are views illustrating a result of a half-immersion test for proving an effect according to the disclosure.

As another test for demonstrating the effect of improvement in corrosion resistance according to the disclosure, a Prohesion solution half-immersion test was conducted to assess the corrosion resistance of the sample. Here, the half-immersion test may refer to a test measuring the corrosion amount by immersing a part of the sample in a test solution and exposing another part of the sample in air.

The test was conducted under the condition of 0.35% ammonium sulfate ((NH□)□SO□) and 0.05% sodium chloride (NaCl) solution, and conducted under the test condition of a Hotplate 50 □ and for 168 h.

Then, the test was conducted with respect to the aluminum alloy (hereinafter, 0.3 Mg sample) including 0.31 wt % of Mg, 0.5 wt % of Zn, 0.08 wt % of Si, and 0.09 wt % of Fe which is an embodiment according to the disclosure.

In addition, the test was conducted with respect to the aluminum alloy (hereinafter, Al1070 sample) including 0.115 wt % of Si, 0.094 wt % of Fe, 0.0053 wt % of Cu, 0.004 wt % of Mn, and 0.004 wt % of Ti, and the aluminum alloy (hereinafter, 0.6Mg sample) including 0.084 wt % of Si, 0.11 wt % of Fe, 0.61 wt % of Mg, and 0.25 wt % of Zn which are the comparison group.

As a result of conducting the half-immersion test with respect to the samples as described above, the test result for each sample with respect to the half-immersed part which is the part of the sample that is exposed both in solution and air may be illustrated in FIGS. 4A to 4C, and the test result for each sample with respect to the immersed part which is the sample immersed in the solution may be illustrated in FIGS. 5A to 5C.

Specifically, FIGS. 4A to 4C are diagrams sequentially illustrating a half-immersed part with respect to the Al1070 sample, the 0.6Mg sample, and 0.3 Mg sample, and FIGS. 5A to 5C are diagrams sequentially illustrating a immersed part with respect to the Al1070 sample, the 0.6Mg sample, and 0.3 Mg sample.

Referring to FIGS. 4A and 4C, the number and area of the pitting of the half-immersed part in the case of the 0.3 Mg sample according to the disclosure being smaller compared to the other sample may be confirmed. In addition, as in the case of FIGS. 5A and 5C, the number and area of pitting of the immersed part in the case of the 0.3 Mg sample according to the disclosure being smaller compared to the other sample may be confirmed.

As a result, when analyzing the result according to the half-immersion test, in the case of the 0.3Mg sample according to the disclosure, that is in the case of the aluminum alloy including 0.31 wt % of Mg, 0.5 wt % of Zn, 0.08 wt % of Si, and 0.09 wt % of Fe, it may be confirmed that the sample has a high corrosion resistance compared to the comparison group.

FIGS. 6A to 7C are views illustrating a result of a CASS test for proving an effect according to the disclosure.

As another test for demonstrating more clearly the effect of improvement in corrosion resistance according to the disclosure, a Copper Accelerate Acetic Acid Salt Spray Test (CASS) was conducted. Here, the CASS test may refer to a method of testing the corrosion resistance of a sample by placing a mixed solution of sodium chloride (NaCl) and Copper(II) Chloride (CuCl₂) in a test chamber and spraying for a certain time, and corresponds to a method of assessing corrosion resistance more intensely compared to the tests described above

The test was conducted under the condition of a solution of 5% sodium chloride (NaCl) and 1 g/3.8 L Copper(II) Chloride, and conducted under the test condition of 720 hours.

Then, the test was conducted with respect to the aluminum alloy (hereinafter, 0.3 Mg sample) including 0.31 wt % of Mg, 0.5 wt % of Zn, 0.08 wt % of Si, and 0.09 wt % of Fe, which is an embodiment according to the disclosure.

In addition, the test was conducted with respect to the aluminum alloy (hereinafter, Al1070 sample) including 0.115 wt % of Si, 0.094 wt % of Fe, 0.0053 wt % of Cu, 0.004 wt % of Mn, and 0.004 wt % of Ti and the aluminum alloy (hereinafter, 0.15Zr sample) including 0.1 wt % of Si, 0.09 wt % of Fe, and 0.16 wt % of Zr, which are the comparison group.

Meanwhile, each sample has been conducted with respect to an aluminum tube having an outer diameter of 6.75 mm and a thickness of 0.85 mm.

As a result of conducting the CASS test with respect to the samples as described above, FIGS. 6A to 6C represent a cross-section of the sample, FIGS. 7A to 7C represent a plane of the sample and a 3D image.

Specifically, the test result with respect to the Al1070 sample is illustrated in FIGS. 6A and 7A, and the test result with respect to the 0.15Zr sample is illustrated in FIGS. 6B and 7B. Further, the test result with respect to the 0.3Mg sample according to an embodiment of the disclosure is illustrated in FIGS. 6C and 7C.

Referring to FIGS. 6A to 6C, the depth of pitting in the case of the Al1070 sample has been measured as 700 μm, the depth of pitting in the case of the 0.15Zr sample has been measured as 450 μm, and the depth of pitting in the case of the 0.3Mg sample has been measured as 100 μm. In other words, the depth of pitting in the case of the 0.3 Mg sample according to the disclosure has been confirmed as being more shallow compared to other samples.

In addition thereto, referring to a corrosion surface 600 in FIG. 6C, in the case of the 0.3Mg sample according to the disclosure, it may be confirmed that a general corrosion similar to the corrosion form of copper is generated and not pitting which is the typical corrosion form of aluminum as described above. That is, in the case of the 0.3Mg sample according to the disclosure, it is apparent that the front surface of the sample has been approximately uniformly eroded. Accordingly, the lifespan of the aluminum tube may increase compared to pitting being deeply generated.

Meanwhile, referring to FIGS. 7A to 7C, the effect of improvement in corrosion resistance according to the disclosure may be more clearly confirmed.

Specifically, as illustrated in FIGS. 7A to 7C, the depth of pitting in the case of the Al1070 sample has been measured as 650 μm, the depth of pitting in the case of the 0.15Zr sample has been measured as 650 μm, and the depth of pitting in the case of the 0.3Mg sample has been measured as 120 μm. In addition, in the case of the 0.3Mg sample according to the disclosure, it may be confirmed once again that corrosion proceeded in the form of general corrosion and not in pitting corrosion form which is a type of local corrosion.

As a result, when analyzing the result according to the CASS test, in the case of the 0.3Mg sample according to the disclosure, that is in the case of the aluminum alloy including 0.31 wt % of Mg, 0.5 wt % of Zn, 0.08 wt % of Si, and 0.09 wt % of Fe, it may be confirmed again that the sample has a high corrosion resistance compared to the comparison group.

FIG. 8 is a view illustrating a result of a CASS test and a SWAAT test according to various composition ranges of the disclosure.

In the above, the test result for comparing the effect of improvement in corrosion resistance according to the disclosure with the aluminum alloy according to the related art has been described, but the test result on the specific composition range of the aluminum alloy according to the disclosure will be described below.

That is, to confirm the effect of improvement in corrosion resistance according to the disclosure in various composition ranges, the CASS test and SWAAT test have been conducted. Here, the SeaWater Acetic Acid Test (SWAAT) may refer to a corrosion test using salt water included in acetic acid, and the meaning of the CASS test is as described above.

The CASS test was conducted under the condition of a solution of 5% sodium chloride (NaCl) and Copper(II) Chloride 1 g/3.8 L for 576 hours. The SWAAT was conducted under the condition of a solution of 5% sodium chloride (NaCl) and 10 ml/1 L acetic acid (CH₃CO₂H) for 576 hours.

The CASS test and the SWAAT test were conducted with respect to the aluminum alloy series in which 0.1 wt % to 0.4 wt % of Mg, 0.1 wt % to 0.7 wt % of Zn, and 0.08 wt % of Si and 0.09 wt % of Fe, and the balance Al are included.

For convenience of description, with respect to the alloy series which is the subject of the test below, only the wt % of Mg and Zn may be represented. For example, with respect to the alloy series including 0.3 wt % of Mg and 0.5 wt % of Zn, 0.08 wt % of Si and 0.09 wt % of Fe and the balance Al, by briefly representing as Al-0.3Mg-0.5Zn alloy series, the alloy series which is the subject of the test will be specified and described.

Referring to FIG. 8 which shows the result according to the disclosure, based on the same wt % of Zn of 0.05 wt % as a reference, the CASS corrosion depth and the SWAAT corrosion depth both decreasing may be confirmed as the wt % of Mg is increased by 0.1, 0.2, and 0.3.

For example, according to the test result as illustrated in FIG. 8, in the case of Al-0.1Mg-0.5Zn alloy series, the CASS corrosion depth is 560 μm and the SWAAT corrosion depth is 220 μm, and in the case of Al-0.2Mg-0.5Zn alloy series, the CASS corrosion depth is 410 μm and the SWAAT corrosion depth is 190 μm. Further, in the case of Al-0.3Mg-0.5Zn alloy series, the CASS corrosion depth is 120 μm and the SWAAT corrosion depth is 70 μm.

Meanwhile, in the case of Al-0.4Mg-0.5Zn alloy series, the CASS corrosion depth is 150 μm and the SWAAT corrosion depth is 90 μm, and it may be confirmed that the corrosion depth is rather deep compared to the Al Al-0.3Mg-0.5Zn alloy series, but it may be confirmed that the corrosion depth is shallow compared to the Al-0.1Mg-0.5Zn alloy series and the Al-0.2Mg-0.5Zn alloy series.

Meanwhile, referring to FIG. 8 which shows the test result, based on the same wt % of Mg of 0.3 wt % as a reference, the CASS corrosion depth and the SWAAT corrosion depth both decreasing may be confirmed as the wt % of Zn is increased by 0.1, 0.3, and 0.5.

For example, according to the test result as illustrated in FIG. 8, in the case of the Al-0.3Mg-0.1Zn alloy series, the CASS corrosion depth is 415 μm and the SWAAT corrosion depth is 130 μm, and in the case of the Al-0.3Mg-0.3Zn alloy series, the CASS corrosion depth is 360 μm and the SWAAT corrosion depth is 100 μm. Further, as described above, in the case of the Al-0.3Mg-0.5Zn alloy series, the CASS corrosion depth is 120 μm and the SWAAT corrosion depth is 70 μm.

Meanwhile, in the case of the Al-0.3Mg-0.7Zn alloy series, the CASS corrosion depth is 320 μm and the SWAAT corrosion depth is 180 μm, and it may be confirmed that the corrosion depth is rather deep compared to Al-0.3Mg-0.5Zn alloy series, but it may be confirmed that the corrosion depth is shallow compared to the Al-0.3Mg-0.1Zn alloy series and the Al-0.3Mg-0.3Zn alloy series.

However, in the case of the alloy series in which 0.7 wt % of Zn is included, the object of the disclosure may be difficult to achieve in terms of securing the processability to the extent of undergoing extrusion and drawing being difficult. That is, the aluminum alloy according to the disclosure may include 0.1 to 0.60 wt % of Zn as described above.

That is, the test as described above may be for confirming the effect of improvement in corrosion resistance according to the disclosure, and the corrosion resistance may be more increased if the wt % of Mg an Zn is further increased, but on the other hand, the securing of the processability to the extent of undergoing extrusion and drawing may be difficult.

Specifically, as illustrated in FIG. 8, in the case Zn exceeds 0.60 wt %, strength may be improved, but the securing of the processability to the extent of undergoing extrusion and drawing may be difficult. Further, although not illustrated, even when the Mg exceeds 0.45 wt %, the strength may be improved, but the securing of the processability to the extent of undergoing extrusion and drawing may be difficult.

Based on the test results as described above, the preferable composition range from among the aluminum alloy series according to the disclosure may be confirmed. Specifically, among the embodiments as described in FIG. 8, it may be confirmed that the Al-0.3Mg-0.5Zn alloy series has the highest corrosion resistance. Further, it may be confirmed that the Al-0.4Mg-0.5Zn alloy series has the second highest corrosion resistance.

Meanwhile, the test result as illustrated in FIG. 8 is merely a part of the material for confirming the effect of improvement in corrosion resistance according to the disclosure. That is, if the test as described above is conducted with a wider numerical range, the preferable composition range according to the disclosure may be confirmed more specifically, which is as described above.

That is, the aluminum alloy according to the disclosure may include 0.1 to 0.45 wt % of Mg and 0.1 to 0.60 wt % of Zn, and 0.05 to 0.1 wt % of Fe, 0.05 to 0.1 wt % of Si and the balance Al. Further, it may be preferable for the Mg to be 0.15 to 0.35 wt %, and Zn to be 0.3 to 0.55 wt %.

In the above, various test results for demonstrating the effect of improving corrosion resistance according to the disclosure have been described. However, those skilled in the art related to the disclosure may confirm the remarkable effect according to the disclosure through various known test methods which may assess the corrosion resistance of the aluminum alloy in addition to the tests as described above.

According to the various embodiments of the disclosure as described above, an aluminum alloy having chloride resistance and corrosion resistance against harmful gas environments as well as processability to the extent of undergoing extrusion and drawing may be provided.

Accordingly, by using the aluminum alloy according to the disclosure rather than using copper to prevent leaks by corrosion of aluminum alloy and water leakage, and to secure corrosion resistance, costs may be reduced.

In particular, based on the aluminum tube manufactured with the aluminum alloy according to the disclosure being used in refrigerators, air conditioners, and the like, which has a use environment where much moister is generated, the effect of improvement in corrosion resistance as described above may be directly connected to an improvement in performance and an extension of the lifespan of the product.

While the present disclosure has been illustrated and described with reference to various example embodiments thereof, the disclosure is not limited to the specific embodiments described. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure, and these changes in form and details are not to be construed individual from the technical idea or scope of the disclosure.

Claims

1. An aluminum alloy, comprising:

0.1 to 0.45 wt % of Mg;

0.1 to 0.60 wt % of Zn;

0.05 to 0.1 wt % of Fe;

0.05 to 0.1 wt % of Si; and

a balance of Al.

2. The aluminum alloy of claim 1, wherein the Mg is 0.15 to 0.35 wt %.

3. The aluminum alloy of claim 1, wherein the Zn is 0.3 to 0.55 wt %.

4. The aluminum alloy of claim 1, wherein a total of wt % of the Mg, the Zn, the Fe and the Si does not exceed 1.0 wt %.

5. The aluminum alloy of claim 1, wherein at least one from among a Mg32(Al, Zn)49 phase and Al3Mg2 phase is formed by the Mg and the Zn.

6. The aluminum alloy of claim 5, wherein a fraction of the Mg32(Al, Zn)49 phase does not exceed 0.05%.

7. The aluminum alloy of claim 5, wherein a fraction of the Al3Mg2 phase does not exceed 0.02%.