JP2006049865A - Corrosion resistant rare earth magnet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a corrosion resistant rare earth magnet provided with a coating with corrosion resistance and heat resistance. <P>SOLUTION: The rare earth permanent magnet is represented by R-T-M-B (R is at least one kind of rare earth elements containing Y, T is Fe or Fe and Co, M is at least one kind of element selected from among Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, and Ta, and contents of the elements are as follows: 5 mass%≤R≤40 mass%, 50 mass%≤T≤90 mass%, 0 mass%≤M≤8 mass%, and 0.2 mass%≤B≤8 mass%). A compound coating of flake fine powder/metal oxide is formed on the surface of rare earth permanent magnet, which is acquired by heating a process film in a process liquid containing at least one kind of flake fine powder selected from among Al, Mg, Ca, Zn, Si, Mn and alloy of them, and at least one kind of metal sol selected from among Al, Zr, Si, and Ti. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, R-T-M-B (R is at least one of rare earth elements including Y, T is Fe or Fe and Co, M is Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb. , Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, Ta, and the content of each element is 5% by mass ≦ R ≦ 40% by mass, 50% by mass ≦ T ≦ 90% by mass, 0% by mass ≦ M ≦ 8% by mass, 0.2% by mass ≦ B ≦ 8% by mass) It relates to a manufacturing method.

  Rare earth permanent magnets are important electrical and electronic materials because of their excellent magnetic properties and are widely used in various fields such as various electric products and computer peripherals. In particular, the Nd-Fe-B permanent magnet has a lower raw material cost because Nd, which is the main element, is abundant than Sm and does not use a large amount of Co, compared to the Sm-Co permanent magnet. It is a very excellent permanent magnet with magnetic properties far superior to those of Sm-Co permanent magnets. For this reason, the amount of Nd-Fe-B permanent magnets used has been increasing in recent years, and the applications are expanding.

  However, since the Nd—Fe—B permanent magnet contains rare earth elements and iron as main components, it has a drawback of being easily oxidized in a short period of time in humid air. For this reason, when incorporated in a magnetic circuit, there is a problem in that the output of the magnetic circuit is reduced due to these oxidations, and rust contaminates the periphery of the device.

  Particularly recently, Nd—Fe—B permanent magnets have begun to be used in motors such as automobile motors and elevator motors, but these are forced to be used in high-temperature and humid environments. Moreover, it must be assumed that it is exposed to moisture containing salt, and higher corrosion resistance is required to be realized at low cost. Further, in these motors, the magnet may be heated to 300 ° C. or higher in a short time in the manufacturing process, and in such a case, heat resistance is also required.

  In order to improve the corrosion resistance of Nd-Fe-B permanent magnets, various surface treatments such as resin coating, Al ion plating, and Ni plating are often performed. It is difficult to cope with the processing with the current technology. For example, resin coating lacks corrosion resistance and does not have heat resistance. Since there is a slight pinhole in Ni plating, rust is generated in moisture containing salt. Although ion plating generally has good heat resistance and corrosion resistance, it requires a large-scale apparatus and it is difficult to realize low cost.

In addition, as a well-known document relevant to this invention, there exist the following.
JP 2003-64454 A JP 2003-158006 A JP 2001-230107 A JP 2001-230108 A

  The present invention was made to provide an R-T-MB-based rare earth permanent magnet such as an Nd magnet that can withstand use under the above-mentioned severe conditions. The magnet has corrosion resistance and heat resistance. An object of the present invention is to provide a corrosion-resistant rare earth magnet provided with a film and a method for producing the same.

  As a result of intensive studies to achieve the above object, the present inventor has found that R-T-MB (where R is at least one rare earth element including Y, T is Fe or Fe and Co, M is Ti, Nb At least one element selected from Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, Ta, The content is expressed by 5 mass% ≦ R ≦ 40 mass%, 50 mass% ≦ T ≦ 90 mass%, 0 mass% ≦ M ≦ 8 mass%, 0.2 mass% ≦ B ≦ 8 mass%, respectively. At least one flaky fine powder selected from Al, Mg, Ca, Zn, Si, Mn and alloys thereof and at least one selected from Al, Zr, Si, Ti on the surface of the rare earth permanent magnet After applying a treatment liquid containing a metal sol of To find that a rare earth magnet having corrosion resistance and heat resistance can be obtained by forming a flaky fine powder / metal oxide composite film on the surface of the magnet, thereby establishing various conditions and completing the present invention. It came to.

  Therefore, the present invention provides R-T-M-B (R is at least one of rare earth elements including Y, T is Fe or Fe and Co, M is Ti, Nb, Al, V, Mn, Sn, Ca, Mg , Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, Ta, and the content of each element is 5 mass% ≦ R ≦ 40 mass, respectively. %, 50 mass% ≦ T ≦ 90 mass%, 0 mass% ≦ M ≦ 8 mass%, 0.2 mass% ≦ B ≦ 8 mass%) on the surface of the rare earth permanent magnet, Al, Mg, Ca , Zn, Si, Mn, and a treatment film with a treatment liquid containing at least one flaky fine powder selected from these alloys and at least one metal sol selected from Al, Zr, Si, Ti Flake-like fine powder / gold obtained by heating Providing corrosion resistance rare earth magnet, characterized in that by forming a composite film of oxide. Further, the present invention provides R-T-M-B (R is at least one of rare earth elements including Y, T is Fe or Fe and Co, M is Ti, Nb, Al, V, Mn, Sn, Ca, Mg , Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, Ta, and the content of each element is 5 mass% ≦ R ≦ 40 mass, respectively. %, 50 mass% ≦ T ≦ 90 mass%, 0 mass% ≦ M ≦ 8 mass%, 0.2 mass% ≦ B ≦ 8 mass%) on the surface of the rare earth permanent magnet, Al, Mg, Ca After applying a treatment liquid containing at least one flaky fine powder selected from Zn, Si, Mn and alloys thereof and at least one metal sol selected from Al, Zr, Si, Ti By heating, flaky fine powder / To provide a method of manufacturing a corrosion-resistant rare earth magnet and forming a composite film of the genus oxide.

  According to the present invention, on the surface of the rare earth permanent magnet, at least one flaky fine powder selected from Al, Mg, Ca, Zn, Si, Mn and alloys thereof, and Al, Zr, Si, Ti By applying and heating a treatment solution containing at least one metal sol selected from among them, and applying a flaky fine powder / metal oxide composite film to the magnet surface, a heat-resistant corrosion-resistant rare earth magnet is inexpensive. The industrial utility value is extremely high.

  In the present invention, as the rare earth permanent magnet, R-TMB-B (R is at least one kind of rare earth element including Y, preferably Nd or Nd as a main component and others, such as an Nd-Fe-B permanent magnet). T is Fe or Fe and Co, M is Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, At least one element selected from Mo, W and Ta, and the content of each element is 5% by mass ≦ R ≦ 40% by mass, 50% by mass ≦ T ≦ 90% by mass, 0% by mass ≦ M ≦ 8, respectively. A rare earth permanent magnet represented by (mass%, 0.2 mass% ≦ B ≦ 8 mass%) is used.

  Here, R is a rare earth element including Y, specifically, at least selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. One kind of rare earth elements, particularly those containing Nd, are preferably used, the content of which is 5% by mass ≦ Nd ≦ 37% by mass, and the content of R is 5% by mass ≦ R ≦ 40% by mass, Preferably, 10% by mass ≦ R ≦ 35% by mass.

  T is Fe or Fe and Co, and the content thereof is 50 mass% ≦ T ≦ 90 mass%, preferably 55 mass% ≦ T ≦ 80 mass%. In this case, the content of Co in T is preferably 10% by mass or less.

  On the other hand, M is at least one element selected from Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, and Ta. And the content thereof is 0 mass% ≦ M ≦ 8 mass%, preferably 0 mass% ≦ M ≦ 5 mass%.

  Further, the magnet contains B in an amount of 0.2 mass% ≦ B ≦ 8 mass%, preferably 0.5 mass% ≦ B ≦ 5 mass%.

In producing an RTMB-based permanent magnet such as the Nd-Fe-B-based permanent magnet used in the present invention, first, the raw material metal is dissolved in a vacuum or an inert gas, preferably in an Ar atmosphere. Make it. As the raw metal, pure rare earth elements, rare earth alloys, pure iron, ferroboron, and alloys thereof are used, but various impurities inevitable in industrial production, typically C, N, O, H, P, S Etc. shall be included. In the obtained alloy, αFe, R-rich phase, B-rich phase and the like may remain in addition to the R ₂ Fe ₁₄ B phase, and solution treatment is performed as necessary. The conditions at that time may be heat-treated for 1 hour or more at a temperature of 700 to 1,200 ° C. in an inert atmosphere such as vacuum or Ar.

  Next, the produced raw material metal is pulverized in steps of coarse pulverization and fine pulverization. The average particle size is preferably in the range of 0.5 to 20 μm. If it is less than 0.5 μm, it is likely to be oxidized and the magnetic properties may be deteriorated. Moreover, when it exceeds 20 micrometers, sinterability may worsen.

  The fine powder is formed into a predetermined shape by a forming press in a magnetic field, followed by sintering. Sintering is performed in a temperature range of 900 to 1,200 ° C. for 30 minutes or more in an inert atmosphere such as vacuum or Ar. After sintering, an aging heat treatment is further performed for 30 minutes or more at a low temperature below the sintering temperature.

  As a method for producing a magnet, not only the above method but also a so-called two-alloy method in which two types of alloy powders having different compositions are mixed and sintered to produce a high-performance Nd magnet may be used. In Japanese Patent No. 2853838, Japanese Patent No. 2853839, Japanese Patent Application Laid-Open No. 5-21218, Japanese Patent Application Laid-Open No. 5-21219, Japanese Patent Application Laid-Open No. 5-74618, and Japanese Patent Application Laid-Open No. 5-182814 are disclosed. The composition of the two types of alloys is determined in consideration of the types and characteristics of these, and by combining these, a high-performance Nd magnet with a high residual magnetic flux density, a high coercive force, and a high energy product can be produced. Methods have been proposed, and the present invention can employ these production methods.

  The permanent magnet in the present invention contains impurity elements unavoidable in industrial production, typically C, N, O, H, P, S, etc., but the total is desirably 2% by mass or less. . If it exceeds 2 mass%, the nonmagnetic component in the permanent magnet increases, and the residual magnetic flux density may be reduced. Further, rare earth elements are consumed by these impurities, resulting in poor sintering and a low coercive force. The lower the total sum of impurities, the higher the residual magnetic flux density and the coercive force.

  In the present invention, a flaky fine powder / metal oxide composite film is formed on the surface of the permanent magnet by applying a treatment liquid containing the flaky fine powder and the metal sol to the surface of the permanent magnet, followed by heating. To do.

  Here, as the flaky fine powder, at least one metal selected from Al, Mg, Ca, Zn, Si, and Mn, an alloy composed of two or more elements, or a mixture thereof can be used. More preferably, a metal selected from Al, Zn, Si, and Mn is used. Further, the shape of the flaky fine powder used in the present invention has an average major axis of 0.1 to 15 μm, an average thickness of 0.01 to 5 μm, and an aspect ratio (average major axis / average thickness). Two or more are preferred. More preferably, the average major axis is 1 to 10 μm, the average thickness is 0.1 to 0.3 μm, and the aspect ratio (average major axis / average thickness) is 10 or more. If the average major axis is less than 0.1 μm, the flaky fine powder is not laminated in parallel with the substrate, and the adhesion may be insufficient. If the average major axis exceeds 15 μm, the flakes are lifted by the solvent of the evaporated processing solution during baking, and the flakes are not stacked in parallel with the substrate, resulting in a film with poor adhesion. In addition, the average major axis is preferably 15 μm or less in view of the dimensional accuracy of the film. When the average thickness is less than 0.01 μm, the surface of the flakes is oxidized at the production stage of the flakes, the film becomes brittle, and the corrosion resistance may deteriorate. If the average thickness exceeds 5 μm, the dispersion of flakes in the treatment liquid becomes poor and the sediment tends to settle, and the treatment liquid becomes unstable, resulting in poor corrosion resistance. If the aspect ratio is less than 2, the flakes are difficult to be stacked in parallel with the substrate, which may cause poor adhesion. There is no upper limit of the aspect ratio, but a large one is not preferable in terms of cost. Usually, the upper limit of the aspect ratio is 100. In addition, you may use a commercial item as these flaky fine powder, for example, brand name Z1051 (made by Benda-Lutz) as Zn flakes, brand name Alpaste 0100M (made by Toyo Aluminum Co., Ltd.), etc. as Al flakes. Can be used.

  Moreover, about the average major axis and average thickness of flake-like fine powder, photography was performed using an optical microscope or an electron microscope, the major axis and thickness of powder were measured, and the average value was calculated | required.

  On the other hand, the metal sol can be at least one metal sol selected from Al, Zr, Si, and Ti. As such a metal sol, a sol having a binding ability in which at least one metal alkoxide selected from Al, Zr, Si, and Ti is partially polymerized by adding water or hydrolyzing with water in air. Can be used.

As described above, the metal sol is obtained by hydrolyzing the above metal alkoxide. In this case, as the metal alkoxide,
A (OR) _a
(However, A represents Al, Zr, Si or Ti, a represents the valence of these metals, and R represents an alkyl group having 1 to 4 carbon atoms.)
The metal alkoxide can be hydrolyzed by a conventional method.

  In addition, these metal alkoxide can use a commercial item. At this time, in order to maintain the stability of the sol, it is possible to add a boron-containing compound such as boric acid or borate at a maximum of 10% by mass of the sol solution. In addition, boron-containing compounds such as boric acid and borates may contribute to improvement of corrosion resistance.

  As the solvent of the treatment liquid, water or an organic solvent can be used, and the blending amount of the flaky fine powder and the metal sol in the treatment liquid is the content of the flaky fine powder and the metal oxide in the composite film described later. Selected to be achieved.

  In preparing this treatment liquid, various additives such as dispersants, anti-settling agents, thickeners, antifoaming agents, anti-skinning agents, desiccants, curing agents and anti-sagging agents are added to improve the performance. You may add up to 10 mass%. Further, as a rust preventive pigment, a zinc phosphate-based, zinc phosphite-based, calcium phosphite-based, aluminum phosphite-based, or aluminum phosphate-based compound may be added up to 20% by mass. These have the property of sequestering metal ions, and have the effect of stabilizing by passivating the surface of Nd magnets and flaky metal fine powders.

  In the present invention, the magnet is immersed in the treatment liquid or coated with the treatment liquid, and then heat-treated to be cured. The dipping and coating methods are not particularly limited, and a film may be formed with the above-described treatment solution by a known method. Further, it is desirable to maintain the heating temperature at 100 ° C. or higher and lower than 500 ° C. for 30 minutes or longer in a vacuum, air, inert gas atmosphere or the like. Although it can be cured even at a temperature lower than 100 ° C., it needs to be left for a long time, which is not preferable in terms of production efficiency. If the curing is insufficient, the adhesion and corrosion resistance may be deteriorated. On the other hand, if the temperature is 500 ° C. or higher, the underlying magnet may be damaged and cause deterioration of magnetic characteristics. The upper limit of the heating time is not particularly limited, but is usually about 1 hour.

  In forming the film in the present invention, repeated coating and heat treatment may be repeated.

  When heated, the metal sol goes through a gel state and becomes a metal oxide, so that the treated film has a structure in which flaky fine powder is bonded to the metal oxide. The reason why the flaky fine powder / metal oxide composite film of the present invention exhibits high corrosion resistance is not clear, but since the fine powder is flaky, it is aligned almost parallel to the substrate, well covered with a magnet, and shielded. It is considered to have an effect. Further, when a metal or alloy having a base potential lower than that of the permanent magnet is used as the flaky fine powder, it is considered that these are oxidized first and have a so-called sacrificial anticorrosive effect that suppresses oxidation of the underlying magnet. Furthermore, the produced | generated film | membrane is an inorganic substance, and also has the characteristics that heat resistance is high.

  In the composite film formed in the present invention, the content of the flaky fine powder is preferably 40% by mass or more, more preferably 45% by mass or more, further preferably 50% by mass or more, and most preferably 60% by mass. That's it. Although the upper limit is appropriately selected, it is preferably 99.9% by mass or less, more preferably 99% by mass or less, and still more preferably 95% by mass or less. If the amount is less than 40% by mass, the amount of fine powder is too small to fully cover the magnet substrate, which may reduce the corrosion resistance.

  In the composite film formed in the present invention, the content of the metal oxide is preferably 0.1% by mass or more, more preferably 1% by mass or more, still more preferably 5% by mass or more, and preferably 60% by mass. % Or less, more preferably 55% by mass or less, still more preferably 50% by mass or less, and most preferably 40% by mass or less. If the amount is less than 0.1% by mass, the bonding component is too small and the adhesion may be insufficient. If it exceeds 60% by mass, the corrosion resistance may decrease.

  In addition, when the total amount of flaky fine powder and a metal oxide is less than 100 mass% in a composite film, the remainder is the said additive and / or a rust preventive pigment.

  The thickness of the film in the present invention is 1 to 40 μm, preferably 5 to 25 μm. If the thickness is less than 1 μm, the corrosion resistance may be insufficient. If the thickness exceeds 40 μm, adhesion may be reduced and delamination may occur easily. -Since the volume of rare earth permanent magnets, such as a B-type permanent magnet, becomes small, there may be a disadvantage in using the magnet.

  In the present invention, the surface of the magnet may be pretreated. Examples of the pretreatment include at least one method selected from acid cleaning, alkali degreasing, and shot blasting. Specifically, (1) acid cleaning + water cleaning + ultrasonic cleaning, (2) alkali cleaning + At least one treatment selected from washing with water and (3) shot blasting is performed.

  As the cleaning liquid used in (1), at least one selected from nitric acid, hydrochloric acid, acetic acid, citric acid, formic acid, sulfuric acid, hydrofluoric acid, permanganic acid, oxalic acid, hydroxyacetic acid, and phosphoric acid is 1 to 1 in total. An aqueous solution containing 20% by mass is used, and the rare earth magnet is immersed at a temperature of room temperature to 80 ° C. By performing acid cleaning, the oxide film on the surface can be removed, and there is an effect of improving the adhesion of the film.

  The alkaline cleaning liquid that can be used in (2) contains a total of 5 to 200 g / L of at least one of sodium hydroxide, sodium carbonate, sodium orthosilicate, sodium metasilicate, trisodium phosphate, sodium cyanide, chelating agent, and the like. What is necessary is just to immerse a rare earth magnet by making it the temperature of normal temperature or more and 90 degrees C or less. Alkali cleaning has the effect of removing dirt from oils and fats adhering to the magnet surface, and improves the adhesion between the film and the magnet.

As the blast material of (3), normal ceramics, glass, plastics, etc. can be used, and the treatment may be performed at a discharge pressure of ^{2 to 3} kgf / cm ² . Shot blasting can remove the oxide film on the surface of the magnet in a dry manner, and also has the effect of improving adhesion.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
In addition, about the average long diameter and average thickness of flaky fine powder, the average value was calculated | required by having photographed using the optical microscope, measuring the long diameter and thickness of 20 powders.
The film thickness of the heated composite film was measured by cutting the magnet piece on which the film was formed, polishing the cut surface, and then measuring the clean cut surface with an optical microscope.

[Examples and Comparative Examples]
An ingot having a composition of 32Nd-1.2B-59.8Fe-7Co by mass ratio was produced by high-frequency melting in an Ar atmosphere. This ingot was coarsely pulverized with a jaw crusher and further finely pulverized with a jet mill using nitrogen gas to obtain a fine powder having an average particle size of 3.5 μm. Next, this fine powder was filled in a mold to which a 10 kOe magnetic field was applied, and molded at a pressure of 1.0 t / cm ² . Next, sintering was performed in vacuum at 1,100 ° C. for 2 hours, and further aging treatment was performed at 550 ° C. for 1 hour to obtain a permanent magnet. A magnet piece having a diameter of 21 mm × thickness of 5 mm was cut out from the obtained permanent magnet, subjected to barrel polishing treatment, and then subjected to ultrasonic water washing, which was used as a test piece.

Examples 1-4
A sol in which aluminum flakes and zinc flakes are dispersed in a metal alkoxide hydrolyzate shown in Table 1 was prepared as a treatment liquid for film formation. The metal alkoxide hydrolyzed solution (sol) was prepared by stirring metal alkoxide 50% by mass, ethanol 44% by mass and pure water 5% by mass under a catalyst of 1 molar concentration-hydrochloric acid 1% by mass for 24 hours. At this time, the treatment liquid is 8% by mass of aluminum flakes (average major axis 3 μm, average thickness 0.2 μm) in the cured composite film, and 80% by mass zinc flakes (average major axis 3 μm, average thickness 0.2 μm). It adjusted so that it might become. This treatment solution was sprayed on the test piece with a spray gun so that the film thickness of the composite film was 10 μm, and then heated in the hot air drying oven at 300 ° C. for 30 minutes to form a film. The contents of aluminum and zinc in the cured composite film were as described above, and the balance was an oxide derived from the hydrolyzed liquid (sol) of the metal alkoxide described in Table 1.

The test piece thus produced was subjected to the following performance test. The performance test method is as follows. The results are shown in Table 1.
(1) Salt spray test According to JIS-Z-2371 neutral salt spray test. 5% saline solution was continuously sprayed at 35 ° C., and the time until tea rust was generated was evaluated.
(2) Appearance of the film after heating at 350 ° C. for 4 hours The appearance change of the film after heating at 350 ° C. for 4 hours was examined visually.

Comparative Examples 1-4
For comparison, a sample in which the test piece was subjected to Al ion plating, Ni plating, and epoxy resin coating with a film thickness adjusted to 10 μm was also prepared and subjected to a salt spray test. Moreover, the external appearance change of the film | membrane after heating at 350 degreeC for 4 hours was investigated visually. The results are shown in Table 2. It can be seen that the permanent magnet of the present invention has both corrosion resistance and heat resistance as compared with other surface-treated permanent magnets.

Examples 5-9
Here, using the treatment liquid used in Example 3, samples having different film thicknesses were prepared, and a cross-cut adhesion test and a salt spray test were performed. The results are shown in Table 3. If the film thickness is too thin, the corrosion resistance is insufficient, and if it is too thick, the adhesion may be inferior.

The cross-cut adhesion test method is as follows.
(3) Cross-cut adhesion test Conforms to the JIS-K-5400 cross-cut test. After making a grid-like cut so that 100 squares of 1 mm can be formed on the film with a cutter knife, press the cellophane tape strongly, pull it off at an angle of 45 degrees, and peel it off. evaluated.

Examples 10-12
Here, a sample similar to Example 2 was prepared except that the content ratio of the flaky fine powder in the composite film was changed, and a salt spray test was performed. As the flaky fine powder contained in the treatment liquid, a mixed powder obtained by mixing flaky aluminum powder and flaky zinc powder (both having an average major axis of 3 μm and an average thickness of 0.2 μm) at a mass ratio of 1:10 is used. It was. The mass ratio of the mixed powder occupying in the treatment liquid was determined by adjusting the content ratio of the flaky fine powder in the composite film to the value described in Table 4. The remainder other than the flaky fine powder in the composite film was an oxide derived from the sol described in Example 2. The results of the salt spray test are shown in Table 4. The film thickness was adjusted to 10 μm. When the content ratio of the flaky fine powder in the film is too small, the corrosion resistance may be deteriorated.

Examples 13-25
Here, a sample similar to Example 1 was prepared except that the shape of the flaky fine powder used was changed, and a cross-cut adhesion test and a salt spray test were performed. The film thickness was 10 μm. The results are shown in Table 5. From Examples 13 to 17, it can be seen that the adhesion may be poor if the average major axis is too short or too long. Moreover, even if average thickness is too thin or too thick from Examples 18-22, corrosion resistance may worsen. From Examples 23 to 25, if the aspect ratio is too small, adhesion may be poor.

Examples 26-29
Here, after the following pretreatment was performed before the treatment, a sample was produced in the same manner as in Example 1.
[Acid cleaning]
Composition: nitric acid 10% (v / v), sulfuric acid 5% (v / v)
Immersion for 30 seconds at 50 ° C [alkali cleaning]
Composition: sodium hydroxide 10 g / L, sodium metasilicate 3 g / L, trisodium phosphate 10 g / L, sodium carbonate 8 g / L, surfactant 2 g / L
Immerse for 2 minutes at 40 ° C [shot blast]
Processing using # 220 aluminum oxide at discharge pressure of 2kgf / cm ²

  The magnet on which the film was formed was subjected to a pressure cooker test at 120 ° C., 2 atm, and 200 hours, and a cross-cut adhesion test was performed on the magnet after this test. The results are shown in Table 6. It can be seen that the adhesion is improved by performing the pretreatment.

Claims (5)

  R-T-M-B (R is at least one of rare earth elements including Y, T is Fe or Fe and Co, M is Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn , Si, Zr, Cr, Ni, Cu, Ga, Mo, W, Ta, and the content of each element is 5 mass% ≦ R ≦ 40 mass%, 50 mass% ≦, respectively. T ≦ 90 mass%, 0 mass% ≦ M ≦ 8 mass%, 0.2 mass% ≦ B ≦ 8 mass%) on the surface of the rare earth permanent magnet, Al, Mg, Ca, Zn, Si, Mn And at least one flaky fine powder selected from these alloys and at least one metal sol selected from Al, Zr, Si, and Ti, by heating a treatment film with a treatment liquid. Flake-like fine powder / metal oxide composite film Corrosion-resistant rare-earth magnet, characterized in that formed comprising.   The shape of the flaky fine powder composing the composite film has an average major axis of 0.1 to 15 μm, an average thickness of 0.01 to 5 μm, and an aspect ratio (average major axis / average thickness) of 2 or more. The corrosion-resistant rare earth magnet according to claim 1, wherein the content ratio of the flaky fine powder in the coating is 40% by mass or more.   The corrosion-resistant rare earth magnet according to claim 1 or 2, wherein the metal sol is obtained by hydrolyzing an alkoxide of a metal selected from Al, Zr, Si, and Ti.   R-T-M-B (R is at least one of rare earth elements including Y, T is Fe or Fe and Co, M is Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn , Si, Zr, Cr, Ni, Cu, Ga, Mo, W, Ta, and the content of each element is 5 mass% ≦ R ≦ 40 mass%, 50 mass% ≦, respectively. T ≦ 90 mass%, 0 mass% ≦ M ≦ 8 mass%, 0.2 mass% ≦ B ≦ 8 mass%) on the surface of the rare earth permanent magnet, Al, Mg, Ca, Zn, Si, Mn And applying a treatment liquid containing at least one flaky fine powder selected from these alloys and at least one metal sol selected from Al, Zr, Si, Ti, and then heating, Flakes fine powder / metal oxide composite on the magnet surface Method for producing a corrosion-resistant rare earth magnet and forming a film. 5. The corrosion-resistant rare earth magnet according to claim 4, wherein the surface of the rare earth permanent magnet is subjected to at least one pretreatment selected from acid cleaning, alkali degreasing, and shot blasting, and then treated with the treatment liquid. Production method.