JP2004190085A - Different-metal member device, and electrolytic corrosion prevention method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a different-metal member device high in electrolytic corrosion prevention effect. <P>SOLUTION: The different-metal member device consists of a first member (1) essentially consisting of a first metal element (Mg), and having a first outside edge part, and a second member (2) essentially consisting of a second metal element (Fe) different from the first metal element, and having a second outside edge part arranged so as to face the first outside edge part. The device is further provided with a separation member (4) disturbing the progress of electrolytic corrosion capable of generating so as to straddle the facing space between the first outside edge part and the second outside edge part. Not only electrolytic corrosion in the facing space between the different-metal member as in the conventional case, but also electrolytic corrosion straddling the facing part can be prevented. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a dissimilar metal member device capable of effectively preventing electrolytic corrosion occurring between dissimilar metal members and a method for preventing the electrolytic corrosion.
[0002]
[Prior art]
Metal materials such as iron and iron alloys or aluminum and aluminum alloys are used for many members. Recently, in order to further reduce the weight of the apparatus, magnesium and magnesium alloys have been used frequently. However, it is difficult to unify a single type of metal material, not only in terms of cost but also in terms of function, etc., so that any type of equipment usually consists of multiple types of metal members. It is configured together.
[0003]
Here, it is known that when dissimilar metal members are disposed close to each other, electrolytic corrosion (electrocorrosion) occurs between the two members using water or the like as a medium. This electrolytic corrosion occurs when various metals have their own corrosion potential (reference potential) and a potential difference is generated between them. In other words, electrolytic corrosion progresses as a whole when a battery is formed using both metals as electrodes and water or salt water or the like interposed between them as an electrolyte. Incidentally, at this time, the metal having a small reference potential serves as an anode to emit electrons, and itself becomes a cation and elutes into the electrolytic solution. On the other hand, a metal having a large reference potential becomes a cathode, receives an electron, and generates an anion such as a hydroxyl group around in the electrolyte solution.
In any case, if the electrolytic corrosion progresses, the function of the member deteriorates and the durability and reliability of the device cannot be secured. Thus, many measures for preventing electrolytic corrosion have been proposed. For example, the following publications disclose such disclosures.
[0004]
[Patent Document 1]
JP-A-7-224944 [Patent Document 2]
JP-A-4-255555 [Patent Document 3]
JP-A-63-282283
[Problems to be solved by the invention]
Patent Literature 1 and Patent Literature 3 propose a method of preventing intrusion of water or the like between contact surfaces of dissimilar metal members to suppress electrolytic corrosion. Further, Patent Document 2 proposes a method in which an insulating material is interposed between dissimilar metal members so that the dissimilar metal members are not brought into direct contact with each other to suppress electrolytic corrosion.
However, the present inventor has conducted research and found that electrolytic corrosion between dissimilar metal members does not always occur between the contact surfaces of the two. That is, if water or the like adheres to the outer periphery of the adjacent dissimilar metal member, the water or the like acts as an electrolytic solution, and a battery is formed so as to straddle the contact surface between the two, and eventually the electrolytic corrosion progresses. It became clear to do. Therefore, simply preventing the intrusion of water or the like between the contact surfaces of the dissimilar metal members and preventing the occurrence of electrolytic corrosion there, the method described in the above-mentioned patent document, Inhibition is inadequate.
[0006]
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a dissimilar metal member device capable of effectively preventing electrolytic corrosion between dissimilar metal members and a method for preventing such corrosion. I do.
[0007]
Means for Solving the Problems and Effects of the Invention
The present inventor has conducted intensive research to solve this problem, and as a result of repeated trial and error, based on the above findings, by preventing batteries from being formed across dissimilar metal members, effective electrolytic corrosion has been achieved. The inventors came up with the idea of suppression and prevention, and developed this to complete the present invention.
(Dissimilar metal member device)
That is, the dissimilar metal member device of the present invention includes a first member having a first outer end mainly composed of a first metal element and a second member mainly composed of a second metal element different from the first metal element. A dissimilar metal member device comprising: a second member having a second outer end disposed opposite to the first outer end;
Further, an isolating member is provided to prevent the progress of electrolytic corrosion that may occur across the space between the first outer end and the second outer end (claim 1).
[0008]
In the case of the dissimilar metal member device of the present invention, the progress of electrolytic corrosion is hindered by the separating member provided between the dissimilar metal members. Here, the difference from the conventional one is that the separating member prevents electric erosion that may occur so as to straddle the space between the first outer end and the second outer end.
That is, since the outer end portion of the member is often exposed to the outside, water, salt water, and the like easily adhere thereto. Then, when water or salt water adheres to the portion where the dissimilar metal members are in a facing relationship, even if the electrolytic corrosion is prevented by a sealing material or the like between both facing surfaces, the water or the like is used as an electrolyte across the outside thereof. A battery is easily formed.
However, in the case of the present invention, since the separating member is provided so as to hinder the formation of the battery, at least the electrolytic corrosion generated over the space between the first outer end and the second outer end is opposed. Progress is inhibited.
[0009]
Note that the isolation member referred to in the present invention is preferably an electrically insulating member having a large electric resistance, but is not limited thereto. As is clear from the above description, any material may be used as long as the formation of a battery using a dissimilar metal member as an electrode is interrupted or suppressed. More specifically, for example, any one that cuts a series of electrolytes such as water for electrically connecting the first outer end and the second outer end is sufficient. Therefore, as far as it is, the isolation member of the present invention may be electrically conductive. More specifically, the isolation member may be made of metal as long as it can prevent the electrolytic corrosion that can occur across the above-mentioned confrontation.
[0010]
However, when a metal material is used for the isolation member, if the reference potential difference between the metal element as the main component and the first metal element or the second metal element is large, new electrolytic corrosion may occur between them. Therefore, when the isolation member is made of a metal material, the isolation member mainly includes an intermediate metal element whose reference potential indicating the degree of electrolytic corrosion is intermediate between the first metal element and the second metal element. It is preferable that the intermediate member be as follows.
[0011]
The reference potential difference between the intermediate member and the first outer end or the reference potential difference between the intermediate member and the second outer end is equal to the reference potential difference between the first outer end and the second outer end. Smaller than. As a result, electrolytic corrosion is less likely to occur between the intermediate member and the first outer end or the second outer end than between the first outer end and the second outer end. Thus, the so-called electrolytic corrosion resistance between the first outer end portion and the second outer end portion is increased, so that the electrolytic corrosion that occurs directly across the two ends is inhibited.
[0012]
Of course, even in the case of the present invention, it is needless to say that it is preferable to provide a sealing material or the like for preventing intrusion of water or the like between the facing surfaces between the dissimilar metal members. However, it is not necessary to provide the sealing material as a separate member, and it is more preferable that the separating member has a sealing function without increasing the number of parts and cost.
[0013]
The “first” or “second” in the present invention is merely a convenient name for distinguishing members and the like. For example, it does not matter whether the first metal element or the second metal element is an electrically base metal (a metal having a low reference potential) or a noble metal (a metal having a low reference potential). If it is necessary to make a distinction for the sake of convenience, the first metal element may be a noble metal (for example, Mg) and the second metal element may be a noble metal (for example, Fe). The material of the first outer end and the second outer end is not limited as long as they are made of dissimilar metals. This is because as long as the dissimilar metal is used, electrolytic corrosion can occur more or less between the two. However, when one of them is Mg or an Mg alloy, the electrolytic corrosion is more likely to proceed, so that the present invention is particularly effective when one of the first metal element and the second metal element is Mg. At this time, the other metal element may be Fe, Al, or any other element. If the first metal element is Mg and the second metal element is Fe, the intermediate metal element may be Zn or Al. If the first metal element is Mg and the second metal element is Al, the intermediate metal element may be Zn.
[0014]
It is sufficient for the first and second members to have such outer ends. That is, it is not necessary that the entirety be made of a metal material. For example, a portion other than the outer end may be a composite member made of resin or the like. Further, the form and function of both members are not limited.
The first outer end and the second outer end may face each other via a gap, or may be in point contact, line contact, or surface contact. Further, for example, it may be connected with a fastener such as a bolt, or may be connected with a sealing material or an adhesive. The problem in the present invention is not electrolytic erosion between the opposing surfaces, but electrolytic erosion straddling the outside of the opposing portion. In most cases, by preventing the electric erosion straddling between the opposing surfaces with the separating member, the electric erosion between the opposing surfaces is also prevented as a result, and the effect of preventing the electric erosion more than before can be obtained as a whole. .
[0015]
The specific region of the outer end portion in the present invention is not specified. This is because the range in which electrolytic corrosion can occur differs depending on the form of the member, the use environment, and the like. To put it bluntly, it is a region including at least the corners of the end portions facing each other. The isolation member may be any as long as it prevents the battery from being formed across the space between the outer ends made of dissimilar metals as described above. Therefore, for example, the separating member of the present invention may be a protruding portion that protrudes outward from the space between the opposing surfaces and cuts off electrical conduction by an electrolytic solution (water, salt water, or the like) that conducts between both outer ends. However, since the amount of protrusion differs depending on the type of the device, the use conditions of the device, the use environment, and the like, it cannot be specified unconditionally.
[0016]
Similarly, the separating member is provided at least between the first outer end and the second outer end so as to interpose the first outer end and the second outer end at a predetermined distance or more. It may be a member. Further, it is more preferable that the separating member is the intermediate member. By adjusting the thickness and the like of the isolation member, it is not possible to unambiguously determine how long the predetermined interval should be. This is because, in this case as well, it differs depending on the form of the device, the use conditions of the device, the use environment, and the like. Although it depends on the size of water droplets adhering between the first outer end and the second outer end, for example, the first outer end mainly composed of Mg and Fe mainly. It is effective if the distance between the second outer end portion and the second outer end portion is 3 mm or more. The separating member (or the intermediate member) may be separated from the first member or the second member. However, it is more preferable that the separating member (or the intermediate member) is integrally formed by joining, casting, or the like because the number of parts can be reduced. .
[0017]
However, it is preferable that the separating member is a covering member that covers at least a corner portion of the first outer end portion and / or the second outer end portion that faces each other. This is because the formation of the battery can be more reliably inhibited by using the insulating member as the covering member. Also, since there is no extra protrusion, it is easy to reduce the size of the apparatus. It is sufficient for the covering member to cover the corners of the outer end portions facing each other, which is likely to cause electrolytic corrosion. However, as the covering area is larger, the effect of preventing electrolytic corrosion is larger and more reliable. Further, it is sufficient to provide the covering member at at least one outer end, but it is more preferable to provide the covering member at both ends. At this time, it is more preferable to seal the outer periphery so that water or the like does not enter between the opposing surfaces of the outer ends. This can suppress and prevent not only the above-described electrolytic corrosion but also crevice corrosion and the like.
[0018]
The covering member may be formed by applying an insulating resin or a liquid gasket, or by attaching or winding an insulating tape or a seal tape. The above-mentioned tapes are preferable as a covering member as long as the covering member merely covers the periphery of the outer end. On the other hand, it is preferable to apply a solution such as the insulating resin, a paste, or the like to a complicated portion (for example, a corner portion) formed on a plurality of surfaces.
[0019]
The dissimilar metal member device of the present invention includes a plurality of members, and each outer end of at least two members is formed of a dissimilar metal. Its function, use, form, etc. are not limited. For example, the second member may be a plate-shaped member provided in close contact with one end of the first member, and the isolation member may be an insulating tape wound around the outer peripheral surface of the plate-shaped member. . If it is about the outer peripheral surface of the plate-shaped member, it can be easily wound and covered with an insulating tape. The plate-like member is, for example, a gasket, a plate-like valve or the like sandwiched between the first member and another member (third member).
[0020]
(Method of preventing electrolytic corrosion of dissimilar metal member devices)
The present invention can be understood not only as the above-described dissimilar metal member device but also as a method for preventing electrolytic corrosion.
That is, the present invention provides a first member having a first outer end mainly composed of a first metal element and a second member mainly composed of a second metal element different from the first metal element. A dissimilar metal member device comprising: a second member having a second outer end disposed opposite to the second member;
An electrical conduction between the first outer end and the second outer end may be obstructed by an isolating member and may occur so as to straddle a space between the first outer end and the second outer end. A method of preventing electrolytic corrosion of a dissimilar metal member device characterized by preventing the progress of electrolytic corrosion may be provided (claim 8).
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described specifically with reference to embodiments.
(1st Embodiment)
FIG. 1 is a schematic sectional view of a compressor 100 which is a first embodiment of a dissimilar metal member device of the present invention. In the compressor 100, an outer frame is formed by a bottomed cylindrical main housing 3 and a shallow bottomed cylindrical end housing 1 (first member: cylindrical member) that closes an open end thereof. Is provided with a sliding piston and the like (not shown). A gasket 2 (second member: plate-like member) serving also as a plate valve is sandwiched between the end housing 1 and the main housing 3. The inside of the compressor 100 is sealed and kept in a lubricating oil atmosphere. An insulating tape 4 (isolation member) is wound around the entire outer peripheral end surface 21 of the gasket 2 and the outer peripheral surface in the vicinity thereof.
[0022]
In the case of this embodiment, the end housing 1 is made of an Mg alloy such as AZ91 (JIS), the main housing 3 is made of an Al alloy such as ADC12 (JIS), and the gasket 2 is made of a cold-rolled steel plate (SPCC: JIS) or the like. It is made of an Fe alloy. Further, as the insulating tape 4, a Teflon-based tape (trade name: Nitoflon adhesive tape No. 903UL, manufacturer: Nitto Denko) was used. In addition, the same type of tape No. No. 903, No. 923, No. Any of the 973 systems can be used. Further, a semiconductive tape or the like may be used.
[0023]
Here, assuming that the insulating tape 4 is not wound, a partially enlarged sectional view of the compressor 100 is shown in FIG. When the compressor 100 in this case is used outdoors or in a humid atmosphere, as shown in FIG. 2, rainwater is applied to the outer peripheral side of the end housing 1 and the gasket 2 so as to straddle the joint portion 61 (between the facing portions). Water droplets 5 such as dew or condensation may adhere. In this case, since the outer peripheral end surface 11 (first outer end) of the end housing 1 and the outer peripheral end surface 21 (second outer end) of the gasket 2 are dissimilar metals, a battery using the water droplet 5 as an electrolyte is formed. Would. Then, Mg having a very low corrosion potential starts to elute into the water droplet 5 from the outer peripheral end face 11. That is, the electrolytic corrosion of the end housing 1 made of the Mg alloy proceeds.
[0024]
However, in the case of the present embodiment, as shown in FIG. 1, the entire outer periphery of the gasket 2, the outer peripheral end surface 11 of the end housing 1 and the outer peripheral end surface 31 of the main housing 3 in the vicinity thereof are sufficiently covered with the insulating tape 4. ing. Therefore, even if the water droplets 5 adhere to the surface of the insulating tape 4, no electrical continuity is formed between the outer peripheral end surface 11 and the outer peripheral end surface 21 and the electrolytic corrosion does not occur.
In the case of the present embodiment, since the insulating tape 4 prevents moisture from entering the joints 61 and 62, there is no need to provide a sealing material such as a liquid gasket, and so-called crevice corrosion is prevented. Is done. Further, since the inside of the compressor 100 is in a lubricating oil atmosphere, there is no occurrence of electrolytic corrosion or the like between the opposing surfaces (between the contact surfaces) inside the joints 61 and 62.
[0025]
(2nd Embodiment)
FIG. 3 shows a schematic sectional view of a compressor 200 which is a second embodiment of the dissimilar metal member device of the present invention. The same members as those of the compressor 100 shown in FIG. 1 are denoted by the same reference numerals.
In the compressor 200, the gasket 2 of the compressor 100 is replaced with a gasket 20 (second member). The gasket 20 is covered with a covering member 204 (isolating member) made of an insulating resin instead of the insulating tape 4 on the entire outer peripheral end face and both corners.
Also in the case of the present embodiment, the covering member 204 blocks the electrical conduction between the outer peripheral end surface 11 of the end housing 1 and the outer peripheral end surface 201 of the gasket 20, so that the electrolytic corrosion of the end housing 1 made of the Mg alloy is suppressed. , Can be prevented.
[0026]
(Third embodiment)
FIG. 4 is a schematic sectional view of a compressor 300 which is a third embodiment of the dissimilar metal member device of the present invention. The same members as those of the compressor 100 shown in FIG. 1 are denoted by the same reference numerals.
This compressor 300 has an annular flange member 41 (projection) between the end housing 1 and the gasket 2 instead of the insulating tape 4 of the compressor 100.
In this case, the outer peripheral end surface 11 of the end housing 1 and the outer peripheral end surface 21 of the gasket 2 are separated from each other by an annular flange member 41 protruding to the outer peripheral side of the joint portion. For this reason, the continuous water droplets 5 and the like as shown in FIG. 2 hardly adhere between the outer peripheral end face 11 and the outer peripheral end face 21. As a result, no battery is formed between the outer peripheral end surfaces via water droplets or the like, and electrolytic corrosion of the end housing 1 made of the Mg alloy is suppressed or prevented.
[0027]
In the present embodiment, a similar annular flange member 43 is also provided between the main housing 3 and the gasket 2, so that the electrolytic corrosion between the main housing 3 and the gasket 2 or the connection between the end housing 1 and the main housing 3 can be performed. Electric corrosion between them did not occur. In the above embodiment, the annular flange members 41 and 43 are separate members from the gasket 2. However, as in the case of the compressor 200, if the annular flange members 41 and 43 and the gasket 2 are integrated, The number of parts and the number of assembly steps are reduced.
[0028]
(Fourth embodiment)
FIG. 5 is a schematic sectional view of a compressor 400 which is a fourth embodiment of the dissimilar metal member device of the present invention. The same members as those of the compressor 100 shown in FIG. 1 are denoted by the same reference numerals.
The compressor 400 has an annular interposed member 45 provided between the end housing 1 and the gasket 2 instead of the insulating tape 4 of the compressor 100. This intervening member 45 is formed integrally with the end housing 1 by casting a considerable amount of Al alloy such as ADC12 (JIS). Since the end housing 1 and the gasket 2 mainly contain Mg and Fe, respectively, the intervening member 45 contains Al (intermediate metal element) as a main component. But also.
[0029]
In the present embodiment, the thickness of the intervening member 45 is set to 3 mm, and the outer peripheral portions (outer end portions) of the end housing 1 and the gasket 2 are sufficiently separated. Accordingly, also in the case of the present embodiment, the continuous water droplets 5 and the like as shown in FIG. 2 hardly adhere between the outer peripheral end surface 11 and the outer peripheral end surface 21, and the battery using the water droplet or the like as a medium between the two outer peripheral end surfaces. Is not formed, and the electrolytic corrosion of the end housing 1 made of the Mg alloy is suppressed and prevented. Furthermore, even if a large water droplet straddling the intervening member 45 adheres between the outer peripheral end surface 11 and the outer peripheral end surface 21, the distance between them increases, the corrosion resistance increases, and the electrolytic corrosion between the two effectively increases. Be inhibited. Moreover, although the interposition member 45 is made of a metal made of an Al alloy, the reference potential difference generated between the end housing 1 and the gasket 2 is smaller than the reference potential difference between the end housing 1 and the gasket 2. For this reason, even if water droplets or the like adhere between the end housing 1 and the interposition member 45, there is little electrolytic corrosion occurring between them.
[0030]
(Fifth embodiment)
FIG. 6 shows a schematic sectional view of a compressor 500 which is a fifth embodiment of the dissimilar metal member device of the present invention. The same members as those of the compressor 100 shown in FIG. 1 are denoted by the same reference numerals.
In the compressor 500, the interposed member 45 of the compressor 400 is an interposed annular flange member 46 having an annular flange. In this case, since both the effects of the third embodiment and the fourth embodiment are obtained, the electrolytic corrosion between the outer peripheral end face 11 and the outer peripheral end face 21 is further suppressed.
In the above embodiment, the intervening member 45 and the intervening member 46 are integrated with the end housing 1, but they may be separated.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a mechanism of generation of electrolytic corrosion according to the present invention.
FIG. 3 is a schematic sectional view showing a second embodiment of the present invention.
FIG. 4 is a schematic sectional view showing a third embodiment of the present invention.
FIG. 5 is a schematic sectional view showing a fourth embodiment of the present invention.
FIG. 6 is a schematic sectional view showing a fifth embodiment of the present invention.
[Explanation of symbols]
1 End housing (first member)
2 Gasket (second member)
3 Main housing 4 Insulating tape (isolation member)
100 compressor

Claims (8)

A first member having a first outer end mainly composed of the first metal element;
A dissimilar metal member device comprising: a second member having a second metal element different from the first metal element as a main component and a second member having a second outer end disposed opposite to the first outer end.
Furthermore, a dissimilar metal member device comprising an isolation member that prevents the progress of electrolytic corrosion that can occur across the space between the first outer end portion and the second outer end portion. 2. The dissimilar metal member device according to claim 1, wherein the isolation member is a covering member that covers at least opposing corners of the first outer end and / or the second outer end. 3. The dissimilar metal member device according to claim 2, wherein the covering member is an insulating tape. The second member is a plate-shaped member provided in close contact with one end of the first member,
The dissimilar metal member device according to claim 1, wherein the separating member is an insulating tape wound around an outer peripheral surface of the plate-shaped member. 2. The heterogeneous member according to claim 1, wherein the isolation member is an intermediate member mainly including an intermediate metal element having a reference potential indicating a degree of electrolytic corrosion between the first metal element and the second metal element. 3. Metal member device. The isolation member is interposed at least between the first outer end and the second outer end so that the distance between the first outer end and the second outer end is a predetermined distance or more. The dissimilar metal member device according to claim 1 or 5, which is a member. The dissimilar metal member device according to claim 1, wherein the first metal element or the second metal element is magnesium (Mg). A first member having a first outer end mainly composed of the first metal element;
A dissimilar metal member device comprising: a second member having a second metal element different from the first metal element as a main component and a second member having a second outer end disposed opposite to the first outer end.
An electrical conduction between the first outer end and the second outer end may be obstructed by an isolating member and may occur so as to straddle a space between the first outer end and the second outer end. A method for preventing electrolytic corrosion of a dissimilar metal member device, characterized by hindering the progress of electrolytic corrosion.

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