EP4206359A1

EP4206359A1 - Ce-containing magnesium alloy sacrificial anode and preparation method therefor and application thereof

Info

Publication number: EP4206359A1
Application number: EP22871071.1A
Authority: EP
Inventors: Sensen XIN; Ming Wang
Original assignee: Midea Group Co Ltd; Wuhu Midea Kitchen and Bath Appliances Manufacturing Co Ltd
Current assignee: Midea Group Co Ltd; Wuhu Midea Kitchen and Bath Appliances Manufacturing Co Ltd
Priority date: 2021-10-25
Filing date: 2022-06-28
Publication date: 2023-07-05
Also published as: CN113930777A; WO2023071259A1; CN116180092A

Abstract

Provided are a Ce-containing magnesium alloy sacrificial anode, a preparation method thereof, and use thereof. The magnesium alloy sacrificial anode includes a magnesium rod body composed of a rare earth magnesium alloy material. The rare earth magnesium alloy material includes Mg and 0.0009% to 3.5% by mass of rare earth elements. The rare earth elements are cerium group rare earth elements including Ce

Description

FIELD

The present disclosure relates to the technical field of alloy materials, and particularly, to a Ce-containing magnesium alloy sacrificial anode, a preparation method thereof, and use thereof.

BACKGROUND

A magnesium alloy has an extremely high electrochemical performance, uniform anode consumption, a long service life, and a large electric energy generation capacity per unit mass, and is an ideal sacrificial anode material.

SUMMARY

In view of the above, the present disclosure provides a Ce-containing magnesium alloy sacrificial anode. The magnesium alloy sacrificial anode comprises a magnesium rod body composed of a rare earth magnesium alloy material. A content of a β phase (Mg₁₇Al₁₂) in the rare earth magnesium alloy material or a structure of the magnesium alloy sacrificial anode is reduced by adding a proper amount of cerium group rare earth elements comprising Ce to reduce a self-corrosion degree of the magnesium alloy sacrificial anode and improve distribution uniformity of the β phase (Mg₁₇Al₁₂) in the structure of the magnesium alloy sacrificial anode. In addition, the Ce also reduces a content of harmful impurity elements such as Si, Fe, Cu, and Ni in the magnesium alloy sacrificial anode, reduces an adverse effect of impurity elements on corrosion of the magnesium alloy sacrificial anode, and enables a high current efficiency of the magnesium alloy sacrificial anode, which may solve problems of a too fast corrosion rate during use of an existing magnesium alloy sacrificial anode and apparent peeling of particulate matter on a surface, and improves the service life and use safety.
The present disclosure further provides a preparation method of the Ce-containing magnesium alloy sacrificial anode.
The present disclosure further provides use of the Ce-containing magnesium alloy sacrificial anode.
The present disclosure further provides an inner container assembly having the Ce-containing magnesium alloy sacrificial anode.
The present disclosure further provides a water heater having the Ce-containing magnesium alloy sacrificial anode or the inner container assembly having the Ce-containing magnesium alloy sacrificial anode.
According to an embodiment in a first aspect of the present disclosure, a Ce-containing magnesium alloy sacrificial anode comprises a magnesium rod body composed of a rare earth magnesium alloy material. The rare earth magnesium alloy material comprises: Mg; and 0.0009% to 3.5% by mass of rare earth elements. The rare earth elements are cerium group rare earth elements comprising Ce.
According to the embodiments of the present disclosure, the Ce-containing magnesium alloy sacrificial anode at least comprises the following beneficial effects. The β phase (Mg₁₇Al₁₂) of the Ce-containing magnesium alloy sacrificial anode has a relatively small content and is uniformly distributed in the structure, which enables the magnesium alloy sacrificial anode to have a current efficiency of greater than 58%, even greater than 60%, which brings a good corrosion resistance effect.
According to the Ce-containing magnesium alloy sacrificial anode of the embodiment in the first aspect of the present disclosure, the rare earth magnesium alloy material comprises 0.001 % to 3.0 % by mass of the rare earth elements.
According to the Ce-containing magnesium alloy sacrificial anode of the embodiment in the first aspect of the present disclosure, the rare earth magnesium alloy material further comprises, in percent by mass, 4% to 7.4% of Al and 2% to 4% of Zn.
The inventor has found that, by appropriately allocating the contents of Ce, Al, and Zn in the magnesium alloy sacrificial anode, it is possible to reduce the content of the β phase (Mg₁₇Al₁₂) in the structure of the magnesium alloy sacrificial anode, reduce the self-corrosion degree of the magnesium alloy sacrificial anode, improve a distribution state of the β phase in the structure, and reduce the content of harmful impurity elements such as Si, Fe, Cu, and Ni in the magnesium alloy sacrificial anode, which enables the magnesium alloy sacrificial anode to have a current efficiency greater than 60%, for example, 62% to 64%.
According to some embodiments of the present disclosure, the rare earth magnesium alloy material in the Ce-containing magnesium alloy sacrificial anode comprises, in percent by mass, 5.3% to 6.7% of Al, 2.5% to 3.5% of Zn, and 0.001% to 3.0% of Ce. According to the present disclosure, the appropriate dosage and ratio of Al, Zn, and Ce is finally obtained through massive selection, and can further improve the distribution of the β phase in the structure to impart the magnesium alloy sacrificial anode with a current efficiency greater than 62.3%.
According to some embodiments of the present disclosure, the rare earth magnesium alloy material in the Ce-containing magnesium alloy sacrificial anode further comprises 0.1% to 0.7% by mass of Mn. For example, a content of Mn is 0.15% to 0.6% by mass. The corporation of a lower content of Mn into the Ce-containing magnesium alloy sacrificial anode facilitates the reaction with impurity elements such as Si, Fe, Cu, or Ni, removing the impurity elements, and improving the current efficiency of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, the rare earth magnesium alloy material in the Ce-containing magnesium alloy sacrificial anode further comprises 0.05% to 1.0% by mass of Ca. The presence of Ca may refine grains and improve the distribution state of the β phase in the structure.
According to some embodiments of the present disclosure, the rare earth magnesium alloy material in the Ce-containing magnesium alloy sacrificial anode further comprises impurity elements. The impurity elements are unavoidable and inevitable in a preparation process of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, in the Ce-containing magnesium alloy sacrificial anode, a single impurity in the impurity elements is at a content smaller than 0.5%. With fewer impurity elements, it is conducive to improving the current efficiency of the prepared magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on a surface of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, in the Ce-containing magnesium alloy sacrificial anode, the impurity elements in the rare earth magnesium alloy material comprises any combination or a single element of Fe, Cu, Ni, or Si. A content of Si is not greater than 0.08%, a content of Ni is not greater than 0.003%, a content of Cu is not greater than 0.02%, and a content of Fe is not greater than 0.005%, in percent by mass. With fewer impurity elements, it is conducive to improving the current efficiency of the prepared magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on the surface of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, in the Ce-containing magnesium alloy sacrificial anode, the impurity elements in the rare earth magnesium alloy material comprises any combination or a single element of Fe, Cu, Ni, or Si. The content of Si is not greater than 0.01%, the content of Ni is not greater than 0.003%, the content of Cu is not greater than 0.02%, and the content of Fe is not greater than 0.005%, in percent by mass. With fewer impurity elements, it is conducive to improving the current efficiency of the prepared magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on the surface of magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, in the Ce-containing magnesium alloy sacrificial anode, a content of a single impurity element in the rare earth magnesium alloy material is not greater than 0.003%, and for example, the content of a single impurity element is not greater than 0.002%, in percent by mass. In this way, it is further conducive to improving the current efficiency of the prepared magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on the surface of magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, a content of a single impurity element in the Ce-containing magnesium alloy sacrificial anode is not greater than 0.001% by mass. It is further conducive to improving the current efficiency of the prepared magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on the surface of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, the contents of the impurity elements in the Ce-containing magnesium alloy sacrificial anode satisfy the following conditions: the content of Si is smaller than 0.001%, the content of Fe is smaller than 0.001%, and the content of Cu is smaller than 0.001% and/or the content of Ni is smaller than 0.001% ("and/or" herein comprises three situations: a first situation is that the content of Si is smaller than 0.001%, the content of Fe is smaller than 0.001%, and the content of Cu is smaller than 0.001%; a second situation is that the content of Si is smaller than 0.001%, the content of Fe is smaller than 0.001%, and the content of Ni is smaller than 0.001%; and a third situation is that the content of Si is smaller than 0.001%, the content of Fe is smaller than 0.001%, the content of Cu is smaller than 0.001%, and the content of Ni is smaller than 0.001%), in percent by mass. With a low impurity content, it is conducive to improving the current efficiency of the prepared magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on the surface of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, the magnesium alloy sacrificial anode has a current efficiency greater than or equal to 58%, and an actual capacitance greater than or equal to 1210A*h/kg. Further, the current efficiency of the magnesium alloy sacrificial anode is greater than or equal to 60%, and the actual capacitance of the magnesium alloy sacrificial anode is greater than or equal to 1210A*h/kg. With a high current efficiency and a high actual capacitance, it is conducive to improving long-term protection of the magnesium alloy sacrificial anode on the water heater or the inner container assembly to prolong the service life of the water heater or the inner container assembly.
According to some embodiments of the present disclosure, when a reference electrode is Cu/CuSO₄, the Ce-containing magnesium alloy sacrificial anode has an open circuit potential ranging from -1.57 V to -1.67 V and a closed circuit potential ranging from - 1.52 V to -1.57 V. Further, when the reference electrode is Cu/CuSO₄, the open circuit potential of the Ce-containing magnesium alloy sacrificial anode ranges from -1.65 V to -1.67 V, and the closed circuit potential of the Ce-containing magnesium alloy sacrificial anode ranges from -1.52 V to -1.57 V.
According to some embodiments of the present disclosure, when a reference electrode is a saturated calomel electrode (SCE), the Ce-containing magnesium alloy sacrificial anode has an open circuit potential ranging from -1.48 V to -1.58 V and a closed circuit potential ranging from -1.48 V to -1.55 V.
According to an embodiment in a second aspect of the present disclosure, a preparation method of the Ce-containing magnesium alloy sacrificial anode of the embodiment of the first aspect of the present disclosure is provided. The preparation method comprises: in an atmosphere of a protective gas, melting Mg, adding Al, Zn, and the cerium group rare earth elements comprising Ce, stirring, holding temperature and standing still, and cooling to obtain the magnesium alloy sacrificial anode.
The preparation method of the Ce-containing magnesium alloy sacrificial anode according to the embodiments of the present disclosure has at least the following beneficial effects: the preparation method is simple, convenient to operate, easy for processing and forming, and suitable for industrial production.
According to some embodiments of the present disclosure, in the preparation method of the Ce-containing magnesium alloy sacrificial anode, the protective substance comprises a protective gas and/or a covering agent. The protective substance is used to isolate air for purpose of preventing oxidization or burning of metals in the preparation process of the magnesium alloy sacrificial anode. Especially, magnesium needs protection because magnesium has a low ignition point and burns easily.
According to some embodiments of the present disclosure, in the preparation method of the Ce-containing magnesium alloy sacrificial anode, the protective gas is selected from CO₂, SF₆ and/or a rare gas. By protecting the preparation process of the Ce-containing magnesium alloy sacrificial anode using the protective gas, it may better prevent the oxidization or burning of the metals.
According to some embodiments of the present disclosure, in the preparation method of the Ce-containing magnesium alloy sacrificial anode, the covering agent is selected from a calcium salt and/or a barium salt, such as calcium chloride, barium chloride. The covering agent may also better isolate the air and prevent the oxidization or burning of the metals.
According to some embodiments of the present disclosure, after the Zn is added and before the CE is added, Mn is added. The addition of Mn is helpful in reducing adverse effects caused by the impurity elements in the magnesium alloy sacrificial anode, improving the current efficiency of the magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on the surface of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, a magnesium ingot is selected as a raw material for the melting, Al is added in a form of an aluminum ingot, and Zn is added in a form of a zinc ingot. Mg in the form of the magnesium ingot, Al in the form of the aluminum ingot, Zn in the form of the zinc ingot have good storage stability and a very convenient addition process.
According to some embodiments of the present disclosure, Mn is added in a form of a magnesium-manganese intermediate alloy or an aluminum-manganese intermediate alloy. Mn in the form of the magnesium-manganese intermediate alloy or the aluminum-manganese intermediate alloy has good storage stability and a very convenient addition process, and is not prone to introduce other impurities.
According to some embodiments of the present disclosure, the cerium group rare earth elements comprising Ce is added in the form of a magnesium-cerium intermediate alloy. Ce in the form of the magnesium-cerium intermediate alloy has good storage stability, and is very convenient to add.
According to some embodiments of the present disclosure, stirring is performed after metal melting. The stirring not only uniformly mixes the components, but also contributes to slag removal and impurity settlement.
According to some embodiments of the present disclosure, a temperature for said holding temperature and standing still is 695°C to 725°C. For example, the temperature for said holding temperature and standing still is 700°C to 720°C. Said holding temperature and standing still lasts for 10 to 45 minutes. For example, said holding temperature and standing still lasts for 15 to 45 minutes. Said holding temperature and standing still enable the prepared magnesium alloy sacrificial anode to have uniform performances.
According to some embodiments of the present disclosure, said melting Mg comprises placing Mg in a crucible (e.g., a graphite crucible, an iron crucible) and performing melting in a heating furnace. In this way, Mg can be sufficiently melted.
According to some embodiments of the present disclosure, in a process of adding Al, Zn, Mn, and Ce, Al is added first, and then Zn, Mn, and Ce are added. The metals are added in this order to prevent the forming of precipitates and improve mixing uniformity in the preparation process of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, air is used for the cooling, which is beneficial to reduce production costs.
According to some embodiments of the present disclosure, the prepared magnesium alloy sacrificial anode is of any shape, for example, a rod shape, a plate shape, a round cake shape, and a hollow rod. The rod shape is helpful in the use of the magnesium alloy sacrificial anode as a sacrificial anode material.
According to an embodiment in a third aspect of the present disclosure, use of the Ce-containing magnesium alloy sacrificial anode according to the embodiment in the first aspect of the present disclosure in corrosion protection of a metallic device is provided.
The use of the Ce-containing magnesium alloy sacrificial anode in the corrosion protection of the metallic device has at least the following beneficial effects: the phenomenon of apparent peeling of particulate matter is not prone to occur on the surface of the Ce-containing magnesium alloy sacrificial anode, and it is therefore possible to improve the service life and use safety of the metallic device, and particularly, improve the service life and the use safety of the metallic device in a high-temperature aqueous environment.
According to some embodiments of the present disclosure, the metallic device is selected from a household appliance.
According to some embodiments of the present disclosure, the household appliance is selected from a water heater or a heating kettle.
The fourth purpose of the present disclosure is to provide an inner container assembly having the Ce-containing magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, the inner container assembly comprises the Ce-containing magnesium alloy sacrificial anode as described above. The inner container assembly further comprises: an inner container body having a cavity formed therein for accommodating water; and a heater disposed on an inner container and heating a water medium in the inner container. The Ce-containing magnesium alloy sacrificial anode is connected to the inner container body to enable the Ce-containing magnesium alloy sacrificial anode to be assembled in the cavity.
According to some embodiments of the present disclosure, a ratio of a weight of the Ce-containing magnesium alloy sacrificial anode to an inner surface area of the cavity of the inner container body is greater than or equal to 150 g/m², for example, 160 to 280 g/m².
According to an embodiment in a fifth aspect of the present disclosure, a water heater or a heating kettle is provided. The water heater or the heating kettle comprises the Ce-containing magnesium alloy sacrificial anode according to the embodiment in the first aspect of the present disclosure or the inner container assembly according to the embodiment in the fourth aspect of the present disclosure.
The water heater according to the embodiments of the present disclosure has at least the following beneficial effects: in the water heater, the magnesium alloy sacrificial anode can effectively protect the inner container assembly, which not only is corrosion resistant, but also has no phenomenon of apparent peeling of particulate matter on the surface. Therefore, the service life and safety of the water heater are effectively improved. The water heater or the heating kettle has a long service life and high use safety. For example, with the same water quality, the service life of the cast magnesium alloy (AZ63B) as the sacrificial anode material in the water heater is 2 years, and the service life of the water heater comprising the Ce-containing magnesium alloy sacrificial anode of the present disclosure is 2.6 to 3.1 years.
In the related art, the magnesium alloy material comprising rare earth is applied in seawater corrosion protection. According to the present disclosure, the magnesium alloy sacrificial anode is applied in the water heater or heating kettle containing high-temperature water, and normal-temperature seawater corrosion protection and high-temperature fresh water corrosion protection are different. Although the magnesium alloy material comprising the rare earth in the related art can be applied in the seawater corrosion protection, a corrosion protection effect thereof in the water heater or heating kettle containing high-temperature water is apparently poorer than that of the magnesium alloy sacrificial anode of the present disclosure.
Additional aspects and advantages of the present disclosure will be provided in part in the following description, and will become apparent in part from the following description or learned from practicing of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a metallographic microscope diagram of a cast magnesium alloy (AZ63B) of Comparative Example 1 of the present disclosure; and
FIG. 2 is a metallographic microscope diagram of a magnesium alloy sacrificial anode prepared in Example 1 of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure are described in detail below. The embodiments described below are illustrative and merely intended to explain rather than limit the present disclosure.
The inventor has found that, during the use of a cast magnesium alloy as a sacrificial anode material, the presence of a cathode phase Mg₁₇ Al₁₂ (a β phase) in a multiphase structure of the cast magnesium alloy results in self-corrosion of the cast magnesium alloy. In addition, an as-cast structure in the cast magnesium alloy has a characteristic of non-uniform distribution, which limits the current efficiency and service life of the cast magnesium alloy as the sacrificial anode material. Generally, the current efficiency of the cast magnesium alloy is merely about 55.7%.
The sacrificial anode material such as the cast magnesium alloy (AZ63B) has a multiphase structure, and the multiphase structure comprises a β phase that may form a self-corrosion cathode, resulting in self loss of AZ63B. In addition, a non-uniform distribution characteristic of the β phase further reduces the current efficiency and service life of the cast magnesium alloy (AZ63B). The current efficiency of the cast magnesium alloy (AZ63B) is 55.7%, and when used as the sacrificial anode material, the cast magnesium alloy (AZ63B) is not resistant to corrosion, has a high corrosion rate, and even has a phenomenon of non-uniform rates of corrosion occurring on a surface of the material, resulting in the phenomenon of apparent peeling of particulate matter on the surface of the material, and further causing a problem of water quality pollution.
Therefore, in order to improve application performance of the magnesium alloy as the sacrificial anode material, it is very necessary to provide a magnesium alloy sacrificial anode that has a reduced content of the β phase (Mg₁₇Al₁₂), is uniformly distributed, and has a high current efficiency.
According to an aspect of the present disclosure, a Ce-containing magnesium alloy sacrificial anode is provided. The Ce-containing magnesium alloy sacrificial anode comprises a magnesium rod body composed of a rare earth magnesium alloy material. The rare earth magnesium alloy material comprises Mg and further comprises, in percent by mass, 0.0009% to 3.5% of cerium group rare earth elements comprising Ce, 4% to 7.4% of Al, and 2% to 4% of Zn. The β phase (Mg₁₇Al₁₂) of the Ce-containing magnesium alloy sacrificial anode is at a relatively small content in the structure and has uniform distribution, which enables the magnesium alloy sacrificial anode to have a current efficiency greater than 60%, for example, 62% to 64%. In some embodiments, for example, the current efficiency is 62.87%, 62.31%, or 63.25%, with a good corrosion resistant effect.
According to some embodiments of the present disclosure, a Ce-containing magnesium alloy sacrificial anode comprises a magnesium rod body composed of a rare earth magnesium alloy material. The rare earth magnesium alloy material comprises Mg and further comprises, in percent by mass, 0.001% to 3.0% of cerium group rare earth elements comprising Ce, 5.3% to 6.7% of Al, and 2.5% to 3.5% of Zn. The appropriate dosage and ratio of the Al, Zn, and Ce are selected to further improve the distribution of the β phase in the structure to impart the magnesium alloy sacrificial anode with a current efficiency greater than 62.3%.
According to some embodiments of the present disclosure, the rare earth magnesium alloy material in the Ce-containing magnesium alloy sacrificial anode further comprises 0.1% to 0.7% by mass of Mn. For example, a content of Mn is 0.15% to 0.6% by mass. The incorporation of a lower content of Mn into the Ce-containing magnesium alloy sacrificial anode facilitates the reaction with impurity elements such as Si, Fe, Cu, or Ni, removing the impurity elements, and improving the current efficiency of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, the rare earth magnesium alloy material in the Ce-containing magnesium alloy sacrificial anode further comprises 0.05% to 1.0% by mass of Ca. The presence of Ca may refine grains and improve the distribution state of the β phase in the structure.
According to some embodiments of the present disclosure, the rare earth magnesium alloy material in the Ce-containing magnesium alloy sacrificial anode further comprises impurity elements. The impurity elements comprise at least one of Si, Fe, Cu, or Ni. The impurity elements may be unavoidable or inevitable in a preparation process of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, in the Ce-containing magnesium alloy sacrificial anode, the impurity elements in the rare earth magnesium alloy material comprises any combination or a single element of Fe, Cu, Ni, or Si. A content of Si is not greater than 0.01%, a content of Ni is not greater than 0.003%, a content of Cu is not greater than 0.02%, and a content of Fe is not greater than 0.005%, in percent by mass. With fewer impurity elements, it is conducive to improving the current efficiency of the prepared magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on a surface of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, in the Ce-containing magnesium alloy sacrificial anode, a content of the impurity elements in the rare earth magnesium alloy material is not greater than 0.006%, for example, smaller than 0.005%, in percent by mass. With fewer impurity elements, it is conducive to improving the current efficiency of the prepared magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on the surface of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, in the Ce-containing magnesium alloy sacrificial anode, a content of a single impurity element in the rare earth magnesium alloy material is not greater than 0.5%, for example, not greater than 0.002%, in percent by mass. It is conducive to reducing the phenomenon of apparent peeling of particulate matter on the surface of the prepared magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, in the Ce-containing magnesium alloy sacrificial anode, a content of a single impurity element in the rare earth magnesium alloy material is not greater than 0.001% by mass. It is further conducive to improving the current efficiency of the prepared magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on the surface of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, in the Ce-containing magnesium alloy sacrificial anode, the contents of the impurity elements in the rare earth magnesium alloy material satisfy the following conditions: the content of Si is smaller than 0.001%, the content of Fe is smaller than 0.001%, and the content of Cu is smaller than 0.001% and/or the content of Ni is smaller than 0.001%, in percent by mass. With a low impurity content, it is conducive to improving the current efficiency of the prepared magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on the surface of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, the Ce-containing magnesium alloy sacrificial anode has a current efficiency greater than or equal to 58%, and an actual capacitance greater than or equal to 1210A*h/kg. Further, the current efficiency of the Ce-containing magnesium alloy sacrificial anode is greater than or equal to 60%, and the actual capacitance of the Ce-containing magnesium alloy sacrificial anode is greater than or equal to 1210A*h/kg. With a high current efficiency and a high actual capacitance, it is conducive to improving long-term protection of the magnesium alloy sacrificial anode on the water heater or the inner container assembly to prolong the service life of the water heater or the inner container assembly.
According to some embodiments of the present disclosure, when a reference electrode is Cu/CuSO₄, the Ce-containing magnesium alloy sacrificial anode has an open circuit potential ranging from -1.57 V to -1.67 V and a closed circuit potential ranging from - 1.52 V to -1.57 V. Further, when the reference electrode is Cu/CuSO₄, the open circuit potential of the Ce-containing magnesium alloy sacrificial anode ranges from -1.65 V to -1.67 V, and the closed circuit potential of the Ce-containing magnesium alloy sacrificial anode ranges from -1.52 V to -1.57 V.
According to some embodiments of the present disclosure, when a reference electrode is a saturated calomel electrode (SCE), the Ce-containing magnesium alloy sacrificial anode has an open circuit potential ranging from -1.48 V to -1.58 V and a closed circuit potential ranging from -1.48 V to -1.55 V.
According to another aspect of the present disclosure, a preparation method of the Ce-containing magnesium alloy sacrificial anode is provided. The preparation method comprises: in an atmosphere of a protective gas, melting Mg, adding Al, Zn, and cerium group rare earth elements comprising Ce, stirring, holding temperature and standing still, and cooling to obtain the Ce-containing magnesium alloy sacrificial anode. The preparation method is simple, convenient to operate, easy for processing and forming, and suitable for industrial production.
According to some embodiments of the present disclosure, a protective substance comprises a protective gas and/or a covering agent. The protective substance is used to isolate air for the purpose of preventing oxidization or burning of metals in the preparation process of the magnesium alloy sacrificial anode. Especially, magnesium needs protection because magnesium has a very low ignition point and burns easily.
According to some embodiments of the present disclosure, the protective gas is selected from CO₂, SF₆, and/or rare gases. The protection for a process of preparing the Ce-containing magnesium alloy sacrificial anode using the protective gas can better prevent the oxidization or burning of metals.
According to some embodiments of the present disclosure, the covering agent is selected from a calcium salt and/or a barium salt, such as calcium chloride, barium chloride. The covering agent can also well isolate the air and prevent the oxidization or burning of metals.
According to some embodiments of the present disclosure, after the Zn is added and before the Ce is added, Mn is added. The addition of Mn is helpful in reducing adverse effects caused by the impurity elements in the magnesium alloy sacrificial anode, improving the current efficiency of the magnesium alloy sacrificial anode, and reducing or preventing the phenomenon of apparent peeling of particulate matter on the surface of the magnesium alloy sacrificial anode.
According to some embodiments of the present disclosure, a magnesium ingot is selected as a raw material for melting, Al is added in a form of an aluminum ingot, and Zn is added in a form of a zinc ingot. Mg in the form of the magnesium ingot, Al in the form of the aluminum ingot, Zn in the form of the zinc ingot have good storage stability and are very convenient to add.
According to some embodiments of the present disclosure, Mn is added in a form of a magnesium-manganese intermediate alloy or an aluminum-manganese intermediate alloy. Mn in the form of the magnesium-manganese intermediate alloy or the aluminum-manganese intermediate alloy has good storage stability and a very convenient addition process, and is not prone to introduce other impurities.
According to some embodiments of the present disclosure, Ce is added in the form of a magnesium-cerium intermediate alloy. Ce in the form of the magnesium-cerium intermediate alloy has good storage stability, and is very convenient to add.
According to some embodiments of the present disclosure, stirring is performed after the metals are melted. The stirring not only uniformly mixes the components, but also contributes to slag removal and impurity settlement.
According to some embodiments of the present disclosure, a temperature for said holding temperature and standing still is 695°C to 725°C. Said holding temperature and standing still lasts for 10 to 35 minutes. Holding temperature and standing still enable the prepared magnesium alloy sacrificial anode to have uniform performances.
According to some embodiments of the present disclosure, said melting Mg comprises placing Mg in a crucible (e.g., a graphite crucible, an iron crucible) and performing melting in a heating furnace. In this way, Mg can be sufficiently melted.
According to some embodiments of the present disclosure, in a process of adding Al, Zn, Mn, and Ce, Al is added first, and then Zn, Mn, and Ce are added. Therefore, the prepared magnesium alloy sacrificial anode has better uniformity.
According to some embodiments of the present disclosure, air is used for said cooling, which is beneficial to reduce production costs.
According to some embodiments of the present disclosure, the prepared magnesium alloy sacrificial anode is of a rod shape.
According to embodiments of another aspect of the present disclosure, the present disclosure provides use of the Ce-containing magnesium alloy sacrificial anode according to the previous embodiments in corrosion protection of a metallic device. Therefore, the Ce-containing magnesium alloy sacrificial anode is applied in a household appliance and serves as the sacrificial anode material, and a phenomenon of apparent peeling of particulate matter is not prone to occur on the surface of the magnesium alloy sacrificial anode, which can improve the service life and use safety of the household appliance.
Another aspect of the present disclosure provides an inner container assembly comprising the Ce-containing magnesium alloy sacrificial anode as described above. The inner container assembly further comprises: an inner container body having a cavity formed therein for accommodating water; and a heater disposed on an inner container and heating a water medium in the inner container. The Ce-containing magnesium alloy sacrificial anode is connected to the inner container body to enable the Ce-containing magnesium alloy sacrificial anode to be assembled in the cavity.
According to some embodiments of the present disclosure, a ratio of a weight of the Ce-containing magnesium alloy sacrificial anode to an inner surface area of the cavity of the inner container body is greater than or equal to 150 g/m², for example, 160 to 280 g/m².
According to another aspect of the present disclosure, a water heater is provided. According to the embodiments of the present disclosure, the water heater comprises the Ce-containing magnesium alloy sacrificial anode. The water heater has a long service life and high use safety. With the same water quality, the service life of the cast magnesium alloy (AZ63B) as the sacrificial anode material in the water heater is 2 years, and the service life of the Ce-containing magnesium alloy sacrificial anode as the sacrificial anode material in the water heater is 2.6 to 3.1 years.
Another aspect of the present disclosure provides a heating kettle. According to embodiments of the present disclosure, the heating kettle comprises the Ce-containing magnesium alloy sacrificial anode in the embodiments as described above. The heating kettle has a long service life and high use safety.
The contents of the present disclosure will be further described in detail below through specific embodiments. The raw materials, reagents, or devices used below may be obtained from a conventional commercial approach unless otherwise specified. Unless otherwise stated, experimental or testing methods are conventional methods in the art.
In the following embodiments, the content of impurity elements being smaller than 0.001% means that the content of the impurity elements in the rare earth magnesium alloy material is greater than 0 and smaller than 0.001%, and the content of impurity elements being smaller than 0.002% means that the content of the impurity elements is greater than 0.001% and smaller than 0.002%. For example, less than 0.001% of Si indicates that the content of Si is smaller than 0.001% and greater than 0, and less than 0.002% of Ni indicates that the content of Ni is smaller than 0.002% and greater than 0.001%.

Comparative Example 1

Components of a rod-shaped cast magnesium alloy (AZ63B) comprised, in percent by mass, 5.3% to 6.7% of Al, 2.5% to 3.5% of Zn, 0.15% to 0.60% of Mn, 0.08% of Si, 0.003% of Fe, 0.01% of Cu, 0.001% of Ni, and a Mg balance. The rod-shaped cast magnesium alloy (AZ63B) was available from a conventional commercial approach.
FIG. 1 is a metallographic microscope diagram of the cast magnesium alloy (AZ63B) of Comparative Example 1 of the present disclosure. In FIG. 1, the black area is a β phase (the Mg₁₇Al₁₂ phase), and the large stretch of contiguous offwhite areas is an α phase (a magnesium matrix phase).
According to GB/T17848-1999, the current efficiency and the corrosion resistant condition of the rod-shaped cast magnesium alloy (AZ63B) of Comparative Example 1 were tested, and the test results are as follows: an open circuit potential was -1.65 V, the current efficiency was 55.7%, a consumption speed of the rod-shaped cast magnesium alloy (AZ63B) was not uniform, and a local region of the surface had a phenomenon of apparent peeling of particles.

Example 1

A Ce-containing magnesium alloy sacrificial anode comprised, in percent by mass, 5.4% of Al, 3.2% of Zn, 0.16% of Mn, 0.01% of Ce, less than 0.001% of Si, less than 0.001% of Fe, less than 0.001% of Cu, less than 0.001% of Ni, and a Mg balance.
The preparation method of the magnesium alloy sacrificial anode comprised: in an atmosphere of protective gases CO₂ and SF₆, in the heating furnace, melting a magnesium ingot in a graphite crucible as a container, then successively adding an aluminum ingot, a zinc ingot, a magnesium-manganese intermediate alloy, and a magnesium-cerium intermediate alloy, stirring to remove the slag, then holding temperature and standing still at 720°C for 20 minutes, and pouring into a round rod mold for air cooling to obtain the rod-shaped magnesium alloy sacrificial anode.
FIG. 2 is a metallographic microscope diagram of a magnesium alloy sacrificial anode prepared in Example 1 of the present disclosure. In FIG. 2, the small black area is a β phase (the Mg₁₇Al₁₂ phase), and the large stretch of contiguous offwhite areas is an α phase (the magnesium matrix phase). Compared with the metallographic microscope diagram of the cast magnesium alloy (AZ63B) of Comparative Example 1 illustrated in FIG. 1, in the magnesium alloy sacrificial anode prepared in Embodiment 1 of the present disclosure, uniformity and connectivity of the β phase in the α phase are improved, and a content of the β phase in the structure of the magnesium alloy sacrificial anode is reduced.

The current efficiency, the corrosion resistant condition, the open circuit potential, and the closed circuit potential of the rod-shaped magnesium alloy sacrificial anode prepared in Example 1 were tested according to GB/T17848-1999. Before the closed-circuit potential of the magnesium alloy sacrificial anode was tested, the surface of the magnesium alloy sacrificial anode was polished to reduce the interference of the surface roughness of the magnesium alloy sacrificial anode on potential measurement. The test results are illustrated in Table 1 and Table 2.

Table 1

	Test Length (mm)	Diameter (mm)	Mass (Before Test) (g)	Mass (After Test) (g)	Actual Capacitance (A*h/kg)	Current Efficiency
Magnesium alloy sacrificial anode prepared in Example 1	21.75	20.495	157.8126	156.0254	1389.48	62.87%

It can be seen from Table 1 that the current efficiency of the rod-shaped magnesium alloy sacrificial anode prepared in Example 1 of the present disclosure is 62.87%. Before and after the test, the rod-shaped magnesium alloy sacrificial anode had a very small mass change, the consumption speed of the rod-shaped magnesium alloy sacrificial anode was uniform, and no apparent particle peeling occurred on the surface. Table 2

1 hour into the test 1 Day 2 Days 3 Days 4 Days

Open Circuit Potential -1.556 / / / /

Closed Circuit Potential -1.538 -1.518 -1.523 -1.494 -1.510
It can be seen from Table 2 that the potential of the rod-shaped magnesium alloy sacrificial anode prepared in Example 1 of the present disclosure was relatively positive with respect to the potential of the cast magnesium alloy (Az63b) in Comparative Example 1. The closed circuit potential of the magnesium alloy sacrificial anode in Example 1 changed less with time, indicating that the magnesium alloy sacrificial anode had a relatively small reaction degree over time.

Example 2

A Ce-containing magnesium alloy sacrificial anode comprised, in percent by mass, 5.8% of Al, 3.0% of Zn, 0.3% of Mn, 1.2% of Ce, less than 0.001% of Si, less than 0.001% of Fe, less than 0.001% of Cu, less than 0.001% of Ni, and a Mg balance.
The preparation method of the magnesium alloy sacrificial anode comprised: under the protection of calcium chloride, in the heating furnace, melting a magnesium ingot in a graphite crucible as a container, then successively adding an aluminum ingot, a zinc ingot, a magnesium-manganese intermediate alloy, and a magnesium-cerium intermediate alloy, stirring to remove the slag, then holding temperature and standing still at 700°C for 40 minutes, and pouring into a round rod mold for air cooling to obtain the rod-shaped magnesium alloy sacrificial anode.

The current efficiency, the corrosion resistant condition, the open circuit potential, and the closed circuit potential of the rod-shaped magnesium alloy sacrificial anode prepared in Example 2 were tested according to GB/T17848-1999. Before the closed-circuit potential of the magnesium alloy sacrificial anode was tested, the surface of the magnesium alloy sacrificial anode was polished to reduce the interference of the surface roughness of the magnesium alloy sacrificial anode on potential measurement. The test results are illustrated in Table 3 and Table 4.

Table 3

	Test Length (mm)	Diameter (mm)	Mass (Before Test) (g)	Mass (After Test) (g)	Actual Capacitance (A*h/kg)	Current Efficiency
Magnesium alloy sacrificial anode prepared in Example 2	21.85	20.395	157.3571	155.5539	1377.0	62.31%

It can be seen from Table 3 that the current efficiency of the rod-shaped magnesium alloy sacrificial anode prepared in Example 2 of the present disclosure was 62.31%. Before and after the test, the rod-shaped magnesium alloy sacrificial anode had a very small mass change, the consumption speed of the rod-shaped magnesium alloy sacrificial anode was uniform, and no apparent particle peeling occurred on the surface. Table 4

1 hour into the test 1 Day 2 Days 3 Days 4 Days

Open Circuit Potential -1.556 / / / /

Closed Circuit Potential -1.538 -1.519 -1.522 -1.490 -1.508
It can be seen from Table 4 that the potential of the rod-shaped magnesium alloy sacrificial anode prepared in Example 2 of the present disclosure was relatively positive with respect to the potential of the cast magnesium alloy (Az63b) in Comparative Example 1. The closed circuit potential of the magnesium alloy sacrificial anode in Example 2 changed less with time, which indicates that the magnesium alloy sacrificial anode had a relatively small reaction degree over time.

Example 3

The Ce-containing magnesium alloy sacrificial anode comprised, in percent by mass, 6.5% of Al, 2.8% of Zn, 0.3% of Mn, 2.4% of Ce, less than 0.001% of Si, less than 0.001% of Fe, less than 0.001% of Cu, less than 0.001% of Ni, and a Mg balance.
The preparation method of the magnesium alloy sacrificial anode comprised: in the atmosphere of protective gases CO₂ and SF₆, in the heating furnace, melting a magnesium ingot in a graphite crucible as a container, then successively adding an aluminum ingot, a zinc ingot, a magnesium-manganese intermediate alloy, and a magnesium-cerium intermediate alloy, stirring to remove slag, then holding temperature and standing still at 710°C for 20 minutes, and pouring into a round rod mold for air cooling to obtain the rod-shaped magnesium alloy sacrificial anode.

The current efficiency, the corrosion resistant condition, the open circuit potential, and the closed circuit potential of the rod-shaped magnesium alloy sacrificial anode prepared in Example 3 are tested according to GB/T17848-1999. Before the closed-circuit potential of the magnesium alloy sacrificial anode was tested, the surface of the magnesium alloy sacrificial anode was polished to reduce the interference of the surface roughness of the magnesium alloy sacrificial anode on potential measurement. The test results are illustrated in Table 5 and Table 6.

Table 5

	Test Length (mm)	Diameter (mm)	Mass (Before Test) (g)	Mass (After Test) (g)	Actual Capacitance (A*h/kg)	Current Efficiency
Magnesium alloy sacrificial anode prepared in Example 3	21.63	20.615	156.9380	155.1603	1397.76	63.25%

It can be seen from Table 5 that the current efficiency of the rod-shaped magnesium alloy sacrificial anode prepared in Example 3 of the present disclosure was 63.25%. Before and after the test, the rod-shaped magnesium alloy sacrificial anode had a very small mass change, the consumption speed of the rod-shaped magnesium alloy sacrificial anode was uniform, and no apparent particle peeling occurred on the surface. Table 6

1 hour into the test 1 Day 2 Days 3 Days 4 Days

Open Circuit Potential -1.519 / / / /

Closed Circuit Potential -1.539 -1.556 -1.523 -1.493 -1.508
It can be seen from Table 6 that the potential of the rod-shaped magnesium alloy sacrificial anode prepared in Example 3 of the present disclosure was relatively positive with respect to the potential of the cast magnesium alloy (Az63b) in Comparative Example 1. The closed circuit potential of the magnesium alloy sacrificial anode in Example 3 changed less with time, which indicates that the magnesium alloy sacrificial anode had a relatively small reaction degree over time.
In the magnesium alloy sacrificial anodes prepared in Examples 1 to 3, the contents of Ce are successively 0.01%, 1.2%, and 2.4%, and the current efficiencies of the prepared magnesium alloy sacrificial anodes are successively 62.87%, 62.31%, and 63.25%. It can be seen therefrom that there was no simple increasing or decreasing relationship between the content of Ce and the current efficiency of the magnesium alloy sacrificial anode. In the above Examples 1 to 3, the components of the magnesium alloy sacrificial anode satisfy the following conditions: the content of Al falls within a range from 5.3% to 6.7%, the content of Zn falls within a range from 2.5% to 3.5%, the content of Mn falls within a range from 0.15% to 0.6%, the content of Ce falls within a range from 0.001% to 3.0%, the content of Si is smaller than 0.001%, the content of Fe is smaller than 0.001%, the content of Cu is smaller than 0.001%, the content of Ni is smaller than 0.001%, and the current efficiencies of the prepared magnesium alloy sacrificial anodes are greater than 62.3%.

Example 4

A Ce-containing magnesium alloy sacrificial anode comprised, in percent by mass, 6.0% of Al, 3.0% of Zn, 0.4% of Mn, 0.01% of Ce, less than 0.001% of Si, less than 0.001% of Fe, less than 0.001% of Ni, and a Mg balance.
The preparation method of the magnesium alloy sacrificial anode comprised: in the atmosphere of protective gases CO₂ and SF₆, in the heating furnace, melting a magnesium ingot in a graphite crucible as the container,, then successively adding an aluminum ingot, a zinc ingot, a magnesium-manganese intermediate alloy, and a magnesium-cerium intermediate alloy, stirring to remove the slag, then holding temperature and standing still at 720°C for 20 minutes, and pouring into a round rod mold for air cooling to obtain the rod-shaped magnesium alloy sacrificial anode.
The current efficiency of the rod-shaped magnesium alloy sacrificial anode prepared in Example 4 was 63.96%. Before and after the test, the rod-shaped magnesium alloy sacrificial anode had a very small mass change, the consumption speed of the rod-shaped magnesium alloy sacrificial anode as the sacrificial anode material was uniform, and no apparent particle peeling occurred on the surface.
A maximum difference between Example 4 and Examples 1 to 3 lies in that no Cu was detected in Example 4, i.e., it can be considered that the impurity element Cu is not present in Example 4, and the current efficiency of the prepared magnesium alloy sacrificial anode is significantly better than the current efficiencies of Examples 1 to 3.

Example 5

The Ce-containing magnesium alloy sacrificial anode comprised, in percent by mass, 4.8% of Al, 3.0% of Zn, 0.4% of Mn, 0.01% of Ce, less than 0.001% of Si, less than 0.001% of Fe, less than 0.001% of Cu, less than 0.001% of Ni, and a Mg balance.
The preparation method of the magnesium alloy sacrificial anode comprised: in the atmosphere of a protective gas CO₂, in the heating furnace, melting a magnesium ingot in a graphite crucible as a container, then successively adding Al, Zn, Mn, and Ce, stirring to remove the slag, then holding temperature and standing still at 725°C for 20 minutes, and pouring into a round rod mold for air cooling to obtain the rod-shaped magnesium alloy sacrificial anode.
The current efficiency of the rod-shaped magnesium alloy sacrificial anode prepared in Example 5 was 62.26%. Before and after the test, the rod-shaped magnesium alloy sacrificial anode had a very small mass change, the consumption speed of the rod-shaped magnesium alloy sacrificial anode as the sacrificial anode material was uniform, and no apparent particle peeling occurred on the surface.
A maximum difference between Example 5 and Example 1 lies in that the content of Al in Example 5 is not within the range from 5.3% to 6.7%, resulting in that the current efficiency of the prepared magnesium alloy sacrificial anode is lower than the current efficiency of the magnesium alloy sacrificial anode in Example 1.

Example 6

The Ce-containing magnesium alloy sacrificial anode comprised, in percent by mass, 5.5% of Al, 2.1% of Zn, 0.6% of Mn, 0.8% of Ce, less than 0.001% of Si, less than 0.001% of Fe, less than 0.001% of Cu, less than 0.001% of Ni, and a Mg balance.
The preparation method of the magnesium alloy sacrificial anode comprised: in the atmosphere of a protective gas SF₆, in the heating furnace, melting a magnesium ingot in a graphite crucible as a container, then successively adding an aluminum ingot, a zinc ingot, a magnesium-manganese intermediate alloy, and a magnesium-cerium intermediate alloy, stirring to remove the slag, then holding temperature and standing still at 715°C for 30 minutes, and pouring into a round rod mold for air cooling to obtain the rod-shaped magnesium alloy sacrificial anode.
The current efficiency of the rod-shaped magnesium alloy sacrificial anode prepared in Example 6 was 62.18%. Before and after the test, the rod-shaped magnesium alloy sacrificial anode had a very small mass change, the consumption speed of the rod-shaped magnesium alloy sacrificial anode as the sacrificial anode material was uniform, and no apparent particle peeling occurred on the surface.
A maximum difference between Example 6 and Example 1 lies in that the content of Zn in Example 6 is not within the range from 2.5% to 3.5%, resulting in that the current efficiency of the prepared magnesium alloy sacrificial anode is lower than the current efficiency of the magnesium alloy sacrificial anode in Example 1.

Example 7

A Ce-containing magnesium alloy sacrificial anode comprised, in percent by mass, 5.8% of Al, 3.1% of Zn, 2.4% of Ce, less than 0.001% of Si, less than 0.001% of Fe, less than 0.001% of Cu, less than 0.001% of Ni, and a Mg balance.
The preparation method of the magnesium alloy sacrificial anode comprised: in the atmosphere of protective gases CO₂ and SF₆, in the heating furnace, melting a magnesium ingot in a graphite crucible as a container, then successively adding an aluminum ingot, a zinc ingot, and a magnesium-cerium intermediate alloy, stirring to remove the slag, then holding temperature and standing still at 710°C for 30 minutes, and pouring into a round rod mold for air cooling to obtain the rod-shaped magnesium alloy sacrificial anode.
The current efficiency of the rod-shaped magnesium alloy sacrificial anode prepared in Example 7 was 62.52%. Before and after the test, the rod-shaped magnesium alloy sacrificial anode had a very small mass change, the consumption speed of the rod-shaped magnesium alloy sacrificial anode as the sacrificial anode material was uniform, and no apparent particle peeling occurred on the surface.
A maximum difference between Example 7 and Example 3 lies in that the magnesium-manganese intermediate alloy is not added in the preparation process of the magnesium alloy sacrificial anode in Example 7, resulting in that the current efficiency of the prepared magnesium alloy sacrificial anode is lower than the current efficiency of the magnesium alloy sacrificial anode in Example 3.

Example 8

A Ce-containing magnesium alloy sacrificial anode comprised, in percent by mass, 6.2% of Al, 2.6% of Zn, 0.18% of Mn, 1.2% of Ce, less than 0.001% of Si, less than 0.002% of Fe, less than 0.001% of Cu, less than 0.002% of Ni, and a Mg balance.
The preparation method of the magnesium alloy sacrificial anode comprises: in the atmosphere of protective gases CO₂ and SF₆, in the heating furnace, melting a magnesium ingot in a graphite crucible as the container, then successively adding an aluminum ingot, a zinc ingot, a magnesium-manganese intermediate alloy, and a magnesium-cerium intermediate alloy, stirring to remove the slag, then holding temperature and standing still at 710°C for 30 minutes, and pouring into a round rod mold for air cooling to obtain the rod-shaped magnesium alloy sacrificial anode.
The current efficiency of the rod-shaped magnesium alloy sacrificial anode prepared in Example 8 was 62.01%. Before and after the test, the rod-shaped magnesium alloy sacrificial anode had a very small mass change, the consumption speed of the rod-shaped magnesium alloy sacrificial anode as the sacrificial anode material was uniform, and no apparent particle peeling occurred on the surface.
A maximum difference between Example 8 and Example 2 lies in that the contents of impurity elements Fe and Ni in the magnesium alloy sacrificial anode in Example 8 are relatively higher, resulting in that the current efficiency of the prepared magnesium alloy sacrificial anode is lower than the current efficiency of the magnesium alloy sacrificial anode in Example 2.

Example 9

A Ce-containing magnesium alloy sacrificial anode comprised, in percent by mass, 6.2% of Al, 2.6% of Zn, 0.18% of Mn, 1.0% of Ce, 0.8% of Ca, 0.08% of Si, 0.003% of Fe, 0.01% of Cu, 0.002% of Ni, and a Mg balance.
The preparation method of the magnesium alloy sacrificial anode comprised: in the atmosphere of protective gases CO₂ and SF₆, in the heating furnace, melting a magnesium ingot in a graphite crucible as the container,, then successively adding an aluminum ingot, a zinc ingot, a magnesium-manganese intermediate alloy, and a magnesium-cerium intermediate alloy, stirring to remove the slag, then holding temperature and standing still at 710°C for 30 minutes, and pouring into a round rod mold for air cooling to obtain the rod-shaped magnesium alloy sacrificial anode.
The current efficiency of the rod-shaped magnesium alloy sacrificial anode prepared in Example 9 was 61.01%. Before and after the test, the rod-shaped magnesium alloy sacrificial anode had a relatively small mass change, the consumption speed of the rod-shaped magnesium alloy sacrificial anode as the sacrificial anode material was uniform, and no apparent particle peeling occurred on the surface.

Example 10

An inner container assembly comprised the Ce-containing magnesium alloy sacrificial anode prepared in Example 1. The inner container assembly further comprised: an inner container body having a cavity formed therein for accommodating water; and a heater disposed on an inner container and heating a water medium in the inner container. The Ce-containing magnesium alloy sacrificial anode was connected to the inner container body to enable the Ce-containing magnesium alloy sacrificial anode to be assembled in the cavity.
A ratio of a weight of the Ce-containing magnesium alloy sacrificial anode to an inner surface area of the cavity of the inner container body was 160 g/m².

Example 11

An inner container assembly comprised the Ce-containing magnesium alloy sacrificial anode prepared in Example 2. The inner container assembly further comprises: an inner container body having a cavity formed therein for accommodating water; and a heater disposed on an inner container and heating a water medium in the inner container. The Ce-containing magnesium alloy sacrificial anode was connected to the inner container body to enable the Ce-containing magnesium alloy sacrificial anode to be assembled in the cavity.
A ratio of a weight of the Ce-containing magnesium alloy sacrificial anode to an inner surface area of the cavity of the inner container body was 280 g/m².

Example 12

A water heater adopted enamel steel as an inner container material, and adopted the magnesium alloy sacrificial anode prepared in Example 1 as a sacrificial anode material.
The water heater prepared in Example 12 did not cause a problem of water quality pollution, which is beneficial to human health.
When the cast magnesium alloy (AZ63B) in Comparative Example 1 is used as the sacrificial anode material to prepare the water heater, with the same water quality (tap water used by people in daily life), the service life of the water heater prepared by using the cast magnesium alloy (AZ63B) in Comparative Example 1 as the sacrificial anode material was 2 years, and the service life of the water heater in Example 12 was 2.9 years.

Example 13

A storage-type water heater comprised the inner container assembly prepared in Example 10.
The storage-type water heater prepared in Example 13 did not cause the problem of water quality pollution, which is beneficial to human health.
The service life of the storage-type water heater prepared in Example 13 was 2.8 years.

Example 14

A heating kettle adopted stainless steel as an inner container material and the magnesium alloy sacrificial anode prepared in Example 3 as a sacrificial anode material.
The heating kettle prepared in Example 14 did not cause the problem of water quality pollution, which is beneficial to human health.
The service life of the heating kettle prepared in Example 14 was 3.1 years.
In the specification, description with reference to the terms "some embodiments", "an example", or "a specific example", etc., means that specific features, structure, materials, or characteristics described in conjunction with the embodiment or example are comprised in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials, or characteristics may be combined in any one or more embodiments or examples in a suitable manner.
Although embodiments of the present disclosure have been illustrated and described, it is conceivable for those skilled in the art that various changes, modifications, replacements, and variations can be made to these embodiments without departing from the principles and ideas of the present disclosure. The scope of the present disclosure is defined by the claims and their equivalents.

Claims

A magnesium alloy sacrificial anode, comprising a magnesium rod body composed of a rare earth magnesium alloy material, wherein the rare earth magnesium alloy material comprises:
Mg; and

0.0009% to 3.5% by mass of rare earth elements,

wherein the rare earth elements are cerium group rare earth elements comprising Ce.
The magnesium alloy sacrificial anode according to claim 1, wherein the rare earth magnesium alloy material comprises 0.001 % to 3.0 % by mass of the rare earth elements.
The magnesium alloy sacrificial anode according to claim 1 or 2, wherein the rare earth magnesium alloy material further comprises, in percent by mass:
4% to 7.4% of Al; and

2% to 4% of Zn.
The magnesium alloy sacrificial anode according to claims 1 to 3, wherein the rare earth magnesium alloy material comprises, in percent by mass:
5.3% to 6.7% of Al;

2.5% to 3.5% of Zn; and

0.001% to 3.0% of Ce.
The magnesium alloy sacrificial anode according to any one of claims 1 to 4, wherein the rare earth magnesium alloy material in the magnesium alloy sacrificial anode further comprises 0.1% to 0.7% by mass of Mn.
The magnesium alloy sacrificial anode according to any one of claims 1 to 5, wherein the rare earth magnesium alloy material in the magnesium alloy sacrificial anode further comprises impurity elements, the impurity elements comprising any combination or a single element of Fe, Cu, Ni, or Si, wherein in percent by mass, a content of Si is not greater than 0.01%, a content of Ni is not greater than 0.003%, a content of Cu is not greater than 0.02%, and a content of Fe is not greater than 0.005%.
The magnesium alloy sacrificial anode according to claim 6, wherein a single impurity in the impurity elements is at a content smaller than 0.5%.
The magnesium alloy sacrificial anode according to any one of claims 1 to 7, wherein the magnesium alloy sacrificial anode has a current efficiency greater than or equal to 58% and an actual capacitance greater than or equal to 1210A*h/kg.
The magnesium alloy sacrificial anode according to claim 8, wherein when a reference electrode is Cu/CuSO₄, the magnesium alloy sacrificial anode has an open circuit potential ranging from -1.57 V to -1.67 V and a closed circuit potential ranging from -1.52 V to -1.57 V.
The magnesium alloy sacrificial anode according to claim 8 or 9, wherein when a reference electrode is a saturated calomel electrode, the magnesium alloy sacrificial anode has an open circuit potential ranging from -1.48 V to -1.58 V and a closed circuit potential ranging from -1.48 V to -1.55 V.
A preparation method of a magnesium alloy sacrificial anode according to any one of claims 3 to 10, comprising:
in the presence of a protective substance, melting Mg,

adding Al, Zn, and a cerium group rare earth elements comprising Ce, stirring,

holding a temperature and standing still, and

cooling to obtain the magnesium alloy sacrificial anode.
A use of a magnesium alloy sacrificial anode according to any one of claims 1 to 11 in a corrosion protection of a metallic device.
An inner container assembly, comprising:
a magnesium alloy sacrificial anode according to any one of claims 1 to 10;

an inner container body having a cavity formed therein for accommodating water; and

a heater disposed on an inner container and heating a water medium in the inner container,

wherein the magnesium alloy sacrificial anode is connected to the inner container body to enable the magnesium alloy sacrificial anode to be assembled in the cavity.
The inner container assembly according to claim 13, wherein a ratio of a weight of the magnesium alloy sacrificial anode to an inner surface area of the cavity of the inner container body is greater than or equal to 150 g/m².
A water heater, comprising a magnesium alloy sacrificial anode according to any one of claims 1 to 10 or an inner container assembly according to claim 13 or 14.