US20200040433A1

US20200040433A1 - Corrosion resistant magnesium alloy

Info

Publication number: US20200040433A1
Application number: US16/347,757
Authority: US
Inventors: Yang Guo; Ming Liu
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2016-11-04
Filing date: 2016-11-04
Publication date: 2020-02-06
Also published as: DE112016007318T5; WO2018082052A1; CN109923229A

Abstract

According to aspects of the present disclosure, a method includes obtaining a first amount of magnesium, a second amount of manganese, and a third amount of a cathodic poison and combining the magnesium, the manganese, and the cathodic poison to thereby form a kinetically hindered magnesium alloy includes less than 1 part by weight of manganese and less than about 5 parts by weight of cathodic poison based on 100 parts of the kinetically hindered magnesium alloy. The cathodic poison is configured to inhibit a cathodic reaction when combined with the magnesium.

Description

TECHNICAL FIELD

The disclosure relates to the field of magnesium alloys and, more specifically, to systems and methods for inhibiting corrosion of magnesium alloys.

BACKGROUND

Magnesium is a lightweight compound that can be used to form components. Magnesium-based components can be used in a variety of applications such as housings and structural components in a variety of industries including automotive, aerospace, and the like. These magnesium-based components can be, for example, structural components, engine components, housings, high-temperature components, and the like. Beneficially, magnesium-based components are formed from the lightest structural metal, provide for high-yield recycling, and provide structural features such as a grain structures that can be beneficial over alternative materials.

SUMMARY

It is desirable to produce magnesium-based components that are resistant to corrosion. Beneficially, methods of producing a kinetically hindered magnesium alloy disclosed herein can be used to form magnesium-based components. The kinetically hindered magnesium alloy is resistant to corrosion and provides additional benefits as will be described further in the detailed description below.
According to aspects of the present disclosure, a method includes obtaining a first amount of magnesium, a second amount of manganese, and a third amount of a cathodic poison and combining the magnesium, the manganese, and the cathodic poison to thereby form a kinetically hindered magnesium alloy includes less than 1 part by weight of manganese and less than about 5 parts by weight of cathodic poison based on 100 parts of the kinetically hindered magnesium alloy. The cathodic poison is configured to inhibit a cathodic reaction when combined with the magnesium.
According to further aspects of the present disclosure, the cathodic poison includes at least one element selected from the group consisting of periodic table of the elements Group 14 alloying elements, periodic table of the elements Group 15 alloying elements, and periodic table of the elements Group 16 alloying elements.
According to further aspects of the present disclosure, the cathodic poison consists of silicon.
According to further aspects of the present disclosure, the cathodic poison consists of a nonmetallic alloying element.
According to further aspects of the present disclosure, the cathodic poison is a nonmetallic alloying element selected from the group consisting of phosphorous, sulfur, and selenium.
According to further aspects of the present disclosure, the cathodic poison consists of at least one periodic table of the elements Group 16 alloying element.
According to further aspects of the present disclosure, the first amount of magnesium includes a hydrogen promotor, and the hydrogen promotor is not removed prior to or during forming the kinetically hindered magnesium alloy.
According to further aspects of the present disclosure, further includes exposes the kinetically hindered magnesium alloy directly to an aqueous environment.
According to further aspects of the present disclosure, further includes forming an automobile component from the kinetically hindered magnesium alloy.
According to aspects of the present disclosure, a method includes obtaining a first amount of magnesium, a second amount of manganese, and a third amount of a cathodic poison and combines the magnesium, the manganese, and the cathodic poison to thereby form a kinetically hindered magnesium alloy includes less than about 6 parts by weight of a combination of the manganese and the cathodic poison based on 100 parts by weight of the kinetically hindered magnesium alloy. The cathodic poison is configured to inhibit a cathodic reaction when combined with the magnesium.
According to further aspects of the present disclosure, the cathodic poison consists of silicon.
According to further aspects of the present disclosure, the cathodic poison consists of a nonmetallic alloying element.
According to further aspects of the present disclosure, the cathodic poison is a nonmetallic alloying element selected from the group consisting of phosphorous, sulfur, and selenium.
According to further aspects of the present disclosure, the cathodic poison consists of a periodic table of the elements Group 16 alloying element.
According to aspects of the present disclosure, a method includes obtaining a first amount of magnesium, a second amount of manganese, and a third amount of a cathodic poison and combining the magnesium, the manganese, and the cathodic poison to thereby form a kinetically hindered magnesium alloy. The cathodic poison is a nonmetallic alloying element is configured to inhibit a cathodic reaction when combined with the magnesium.
According to further aspects of the present disclosure, the kinetically hindered magnesium alloy includes less than about 6 parts by weight of a combination of the manganese and the cathodic poison.
According to further aspects of the present disclosure, the kinetically hindered magnesium alloy includes less than 1 part by weight of the manganese and less than about 5 parts by weight of the cathodic poison.
According to further aspects of the present disclosure, the nonmetallic alloying element is selected from the group consisting of phosphorous, sulfur, and selenium.
According to further aspects of the present disclosure, further includes exposes the kinetically hindered magnesium alloy directly to an aqueous environment.
According to further aspects of the present disclosure, further includes forming an automobile component from the kinetically hindered magnesium alloy.
The above features and advantages and other features and advantages of the present disclosure are readily apparent from the following detailed description.

DETAILED DESCRIPTION

Magnesium-based products corrode when exposed to aqueous environments. The corrosion proceeds through a cathodic reaction. The corrosion reaction for water contacting a magnesium substrate can be expressed as follows.
Mg+2H₂O→Mg(OH)₂+H_2(g) (1)
The anodic half-reaction can be expressed as follows.
Mg→Mg²⁺+2e ⁻ (2)
The cathodic half-reaction can be expressed as follows.
H⁺ +e ⁻→H_(ad) (3)
Adsorbed hydrogen H_(ad)produced by the cathodic half-reaction, equation (3), remains adsorbed to a first active site of the magnesium substrate until another adsorbed hydrogen H_(ad)occupies a second active site of the magnesium substrate that is near enough to the first active site to allow the two adsorbed hydrogen H_(ad)atoms to evolve gaseous diatomic hydrogen H₂.
Beneficially, according to aspects of the present disclosure, magnesium, manganese, and a cathodic poison can be combined to form a kinetically hindered magnesium alloy that is configured to inhibit the cathodic reaction to thereby inhibit hydrogen evolution and corrosion of magnesium-based products formed from the kinetically hindered magnesium alloy. A cathodic poison is any element or combination of elements that kinetically inhibits the cathodic reaction. In some aspects, the cathodic poison is configured to inhibit the cathodic reaction when combined with the magnesium. The cathodic poison can kinetically inhibit the cathodic reaction by altering the number of sites available for the cathodic reaction to occur, increase distances between sites for the cathodic reaction to occur, combinations thereof, and the like.
In some aspects, the cathodic poison includes alloying elements from periodic table of the elements Groups 14-16. As used herein, “alloying elements” refers to elements that are capable of forming an alloy with magnesium either alone or in combination with other elements. Periodic table of the elements Group 14 alloying elements include, for example, silicon, germanium, tin, and lead. Periodic table of the elements Group 15 alloying elements include, for example, phosphorous, arsenic, antimony, and bismuth. Periodic table of the elements Group 16 alloying elements include, for example, sulfur, selenium, tellurium, and polonium.
In some aspects, the cathodic poison is silicon. Surprisingly, silicon can be used as the cathodic poison to inhibit to inhibit the cathodic reaction and the generation of gaseous hydrogen when alloyed with magnesium. Beneficially, silicon is more abundant, less expensive, easier to process and purify by known methods in industries such as microelectronics manufacturing, and less dangerous to handle and incorporate than metallic poisons such as mercury, indium, and gallium.
In some aspects, the cathodic poison is a nonmetallic alloying element. Surprisingly, nonmetallic alloying elements can be used as the cathodic poison to inhibit the cathodic reaction and the generation of gaseous hydrogen when alloyed with magnesium. In some aspects, the cathodic poison is a nonmetallic alloying element consisting of elements selected from nonmetallic elements. More particularly, the nonmetallic alloying element can be selected from the group consisting of phosphorous, sulfur, and selenium. Beneficially, nonmetallic alloying elements can be more abundant, less expensive, easier to process, and less dangerous to handle and incorporate into the alloy than metallic poisons such as mercury, indium, and gallium.
In some aspects, the cathodic poison is an alloying element selected from periodic table of the elements Group 16. Surprisingly, alloying elements from periodic table of the elements Group 16 can be used as the cathodic poison to inhibit to inhibit the cathodic reaction and the generation of gaseous hydrogen when alloyed with magnesium. Beneficially, one or more alloying elements selected from periodic table of the elements Group 16 can be used to enhance machinability and other properties of the resulting alloy.
In some aspects, a method of forming the kinetically hindered magnesium alloy includes obtaining a first amount of magnesium, a second amount of manganese, and a third amount of cathodic poison. The first amount of magnesium may be obtained through, for example, obtaining commercially pure magnesium (e.g., 99.8% Mg). Alternatively, the first amount of magnesium may be obtained through, for example, obtaining a magnesium alloy consisting of magnesium and other compounds. Magnesium alloys used to obtain the first amount of magnesium can include magnesium mixed with, for example, aluminum, zinc, manganese, silicon, copper, rare earth elements, zirconium, combinations thereof, and the like. Some example magnesium alloys suitable for obtaining the first amount of magnesium include AZ91 (about 9 parts by weight Al and about 1 part by weight Zn with the balance being substantially Mg), AZ92(about 9 parts by weight Al and about 2 parts by weight Zn with the balance being substantially Mg), AZ63 (about 6 parts by weight Al and about 3 parts by weight Zn with the balance being substantially Mg), A10 (about 10 parts by weight Al with the balance being substantially Mg).
The method further includes combining the obtained magnesium, manganese, and cathodic poison to form the kinetically hindered magnesium alloy through any suitable alloying process as would be recognized by one of ordinary skill in the art. In some aspects, the kinetically hindered magnesium alloy includes less than 1 part by weight of manganese and less than about 5 parts by weight of cathodic poison. In some aspects, the kinetically hindered magnesium alloy includes less than about 6 parts by weight of manganese and cathodic poison. The balance of the kinetically hindered magnesium alloy is generally magnesium. In some aspects, the kinetically hindered magnesium alloy is about 88 parts by weight of magnesium. In some aspects, the kinetically hindered magnesium alloy is at least 94 parts by weight of magnesium.
The materials used to obtain the first amount of magnesium generally include at least one hydrogen promotor (such as iron, nickel, copper, cobalt, and the like) as a contaminant. The hydrogen promoter contributes to corrosion of the magnesium and components formed therefrom. While the materials can be purified to minimize the at least one hydrogen promotor, the at least one hydrogen promotor generally cannot be eliminated entirely. Thus, the at least one hydrogen promoter will continue to promote the cathodic reaction. Beneficially, aspects of the present disclosure provide for forming kinetically hindered magnesium alloys that inhibit the cathodic reaction even in the presence of the at least one hydrogen promotor. In some aspects, the hydrogen promotor is not removed prior to or during forming the kinetically hindered magnesium alloy. As such, costs associated with purification of the materials can be avoided while achieving significant corrosion resistance.
In some aspects, a magnesium-based component is formed from the kinetically hindered magnesium alloy. The magnesium-based component can be, for example, an automobile component.
Some magnesium-based components have a protective coating applied to surfaces of the components to prevent contact between an aqueous environment and a magnesium substrate of the magnesium-based component. These protective coatings can include at least one layer of material on the surfaces of the magnesium-based components. Detrimentally, any damage to the protective coating, such as a scratch that reaches the magnesium substrate, exposes magnesium within the magnesium substrate to an aqueous environment. As such, the coating can be rendered ineffective by contact or ordinary wear and weathering. Beneficially, aspects of the present disclosure provide for forming kinetically hindered magnesium alloys that can be exposed directly to an aqueous environment without the protective coating. Kinetically hindered magnesium alloys in accord with the present disclosure continue to inhibit cathodic reactions after a surface of the magnesium-based component is damaged or removed because the kinetically hindered magnesium alloy itself inhibits corrosion. Additionally, the surface coatings tend to be formed from expensive materials such as noble metals. As such, costs associated with applying protective coatings to the magnesium-based components and obtaining materials for the protective coating can be avoided while achieving significant corrosion resistance.
Beneficially, forming components from the kinetically hindered magnesium alloy results in magnesium-based components that are resistant to corrosion. Further, these magnesium-based components formed from the kinetically hindered magnesium alloy provide a practical alternative to using other materials, such as aluminum or steel, which can reduce overall weight of the components, reduce costs of acquiring raw materials, reduce costs of manufacturing, reduce costs associated with recycling of components, increase yield of recycled components, and/or reduce overall vehicle weight.
While the best modes for carrying out the disclosure have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs, embodiments, and aspects for practicing the disclosure within the scope of the appended claims.

Claims

1. A method comprising:

obtaining a first amount of magnesium, a second amount of manganese, and a third amount of a cathodic poison, the cathodic poison configured to inhibit a cathodic reaction when combined with the magnesium; and

combining the magnesium, the manganese, and the cathodic poison to thereby form a kinetically hindered magnesium alloy including less than 1 part by weight of manganese and less than about 5 parts by weight of cathodic poison based on 100 parts of the kinetically hindered magnesium alloy.

2. The method of claim 1, wherein the cathodic poison includes at least one element selected from the group consisting of periodic table of the elements Group 14 alloying elements, periodic table of the elements Group 15 alloying elements, and periodic table of the elements Group 16 alloying elements.

3. The method of claim 1, wherein the cathodic poison consists of silicon.

4. The method of claim 1, wherein the cathodic poison consists of a nonmetallic alloying element.

5. The method of claim 1, wherein the cathodic poison is a nonmetallic alloying element selected from the group consisting of phosphorous, sulfur, and selenium.

6. The method of claim 1, wherein the cathodic poison consists of at least one periodic table of the elements Group 16 alloying element.

7. The method of claim 1, wherein the first amount of magnesium includes a hydrogen promotor, and wherein the hydrogen promotor is not removed prior to or during forming the kinetically hindered magnesium alloy.

8. The method of claim 1, further comprising exposing the kinetically hindered magnesium alloy directly to an aqueous environment.

9. The method of claim 1, further comprising forming an automobile component from the kinetically hindered magnesium alloy.

10. A method comprising:

combining the magnesium, the manganese, and the cathodic poison to thereby form a kinetically hindered magnesium alloy including less than about 6 parts by weight of a combination of the manganese and the cathodic poison based on 100 parts by weight of the kinetically hindered magnesium alloy.

11. The method of claim 10, wherein the cathodic poison consists of silicon.

12. The method of claim 10, wherein the cathodic poison consists of a nonmetallic alloying element.

13. The method of claim 10, wherein the cathodic poison is a nonmetallic alloying element selected from the group consisting of phosphorous, sulfur, and selenium.

14. The method of claim 10, wherein the cathodic poison consists of a periodic table of the elements Group 16 alloying element.

15. A method comprising:

obtaining a first amount of magnesium, a second amount of manganese, and a third amount of a cathodic poison, the cathodic poison being a nonmetallic alloying element configured to inhibit a cathodic reaction when combined with the magnesium; and

combining the magnesium, the manganese, and the cathodic poison to thereby form a kinetically hindered magnesium alloy.

16. The method of claim 15, wherein the kinetically hindered magnesium alloy includes less than about 6 parts by weight of a combination of the manganese and the cathodic poison.

17. The method of claim 15, wherein the kinetically hindered magnesium alloy includes less than 1 part by weight of the manganese and less than about 5 parts by weight of the cathodic poison.

18. The method of claim 15, wherein the nonmetallic alloying element is selected from the group consisting of phosphorous, sulfur, and selenium.

19. The method of claim 15, further comprising exposing the kinetically hindered magnesium alloy directly to an aqueous environment.

20. The method of claim 15, further comprising forming an automobile component from the kinetically hindered magnesium alloy.