Corrosion protection of NdFeB magnets

Mitchell, P.J.

doi:10.1109/20.104575

Cited by 59 publications

(21 citation statements)

References 3 publications

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“…Majority of electroless coating studies are limited to Nd-Fe-B powder [14][15][16] and were carried out mainly with a purpose of improving the corrosion resistance of the magnet. However, the use of electroless plating method has not been yet fully explored for the purpose of developing hard-soft exchange-spring magnets [17].…”

Section: Introductionmentioning

confidence: 99%

Magnetic Properties Hard-Soft SmCo5-FeNi and SmCo5-FeCo Composites Prepared by Electroless Coating Technique

Lamichanne¹,

Ma²,

Mishra

et al. 2012

OJCM

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Composites of SmCo 5 -FeNi and SmCo 5 -FeCo, hard-soft magnetic materials, have been synthesized via electroless plating of magnetically hard SmCo 5 powder particles with magnetically soft FeNi and FeCo, respectively. The influence of coating thickness of soft magnetic layers on the structure and magnetic properties of the composite has been studied. Overall FeNi coating was found to be less dense compared to FeCo for the same plating duration. Structurally the coat ing was found to be nodular in morphology. These coating have dramatic effect on the overall magnetic property of the composite. As compared to FeNi coated SmCo 5 composite, two-fold increase in the saturation magnetization has been observed upon coating SmCo 5 (M s ~ 28 emu/g) with FeCo to a value 56 emu/g. The coercivity of composite powder was found to decrease with increasing the coating layer thickness. The absence of exchange spring behavior in the hard-soft composite is attributed to magnetically soft layer thickness exceeding the theoretical length limit for exchange-spring coupling.

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Section: Introductionmentioning

confidence: 99%

Magnetic Properties Hard-Soft SmCo5-FeNi and SmCo5-FeCo Composites Prepared by Electroless Coating Technique

Lamichanne¹,

Ma²,

Mishra

et al. 2012

OJCM

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“…To overcome this problem, a lot of research work on the protective coating on Nd-Fe-B magnet has been carried out [2][3][4][5][6][7][8]. The coating material can be generally categorized into two groups: polymers, including epoxy resin [2,3] and bismaleimide (BMI) resin [4], and metals [2,[5][6][7][8]. Generally epoxy coating is easy to apply and less costly.…”

Section: Introductionmentioning

confidence: 99%

“…Metallic protection is mainly achieved by two types of techniques: vapour deposition and electrochemical plating [5]. Post-deposition heat treatment may be necessary after the coating is carried out to improve the adhesion between the coating and the magnet.…”

Section: Introductionmentioning

confidence: 99%

Multi-layered electroless Ni–P coatings on powder-sintered Nd–Fe–B permanent magnet

Zhong

et al. 2006

Journal of Magnetism and Magnetic Materials

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“…on Nd-Fe-B magnets have been reported in the literature. [3][4][5][6] On the other hand, among the different types of polymer coatings, only epoxy resin has been attempted on Nd-Fe-B magnets. The time to failure of various epoxy-coated NdFe-B magnets in the ASTM normal salt spray ͑NSS͒ test ͑35°C, 5% NaCl, pH 6.5-7.2͒ in different studies ranged between 100 and 200 h, 6,7 which was comparable to a semibright Ni coating of 30 m ͑Ref.…”

Section: Introductionmentioning

confidence: 99%

Corrosion protection of Nd–Fe–B magnets by bismaleimide coating

Cheng

Man

Chan

et al. 1999

Journal of Applied Physics

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Enhancement of coercivity for Nd-Fe-B thin films by the infiltration of Nd-Cu alloy cap layer J. Appl. Phys. 110, 023903 (2011) Demagnetizing effects in granular hard magnetic bodies J. Appl. Phys. 109, 093901 (2011) Dysprosium-saving improvement of coercivity in Nd-Fe-B sintered magnets by Dy2S3 additions J. Appl. Phys. 109, 083916 (2011) Effect of surrounding air region size on finite element modeling for permanent magnetic solenoids J. Appl. Phys. 109, 07A757 (2011) The effect of doping element Zr on anisotropy and microstructure of SmCo7xZrx J. Appl. Phys. 109, 07A748 (2011) Additional information on J. Appl. Phys. Samples of Nd-Fe-B were coated with bismaleimide ͑BMI͒, a resin which is well known for its desirable barrier, mechanical, and thermal properties but has not been used as a coating material. The performance of BMI-coated samples ͑average coating thickness ϳ15 m͒ was compared with commercial epoxy-coated samples ͑average coating thickness ϳ20 m͒ in a series of tests. In the copper-accelerated acetic acid-salt spray test, the epoxy-coated samples failed badly ͑damaged area Ͼ50%͒ within 20 h while the BMI-coated samples showed no sign of failure up to 200 h. Using the cross-cut tape test for adhesion strength ͑ASTM D 3359͒, the commercial epoxy coatings suffered 25% area detachment while for the BMI coatings, no detachment was observed. The scratch resistance of the BMI coatings, measured in terms of scratch depth in the pin scratch test, was about 1.5 that of the commercial epoxy coatings, and the Vickers hardness was higher by a factor of about 2.5. When magnetized under the same magnetizing field, there was no significant difference in the magnetization obtained among bare, epoxy-coated, and BMI-coated samples. These results suggest that BMI coatings are excellent for protection of the Nd-Fe-B magnets against corrosion and function better than the commonly used epoxy resin.

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Corrosion protection of NdFeB magnets

Cited by 59 publications

References 3 publications

Magnetic Properties Hard-Soft SmCo<sub>5</sub>-FeNi and SmCo<sub>5</sub>-FeCo Composites Prepared by Electroless Coating Technique

Magnetic Properties Hard-Soft SmCo<sub>5</sub>-FeNi and SmCo<sub>5</sub>-FeCo Composites Prepared by Electroless Coating Technique

Multi-layered electroless Ni–P coatings on powder-sintered Nd–Fe–B permanent magnet

Corrosion protection of Nd–Fe–B magnets by bismaleimide coating

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Corrosion protection of NdFeB magnets

Cited by 59 publications

References 3 publications

Magnetic Properties Hard-Soft SmCo&lt;sub&gt;5&lt;/sub&gt;-FeNi and SmCo&lt;sub&gt;5&lt;/sub&gt;-FeCo Composites Prepared by Electroless Coating Technique

Magnetic Properties Hard-Soft SmCo&lt;sub&gt;5&lt;/sub&gt;-FeNi and SmCo&lt;sub&gt;5&lt;/sub&gt;-FeCo Composites Prepared by Electroless Coating Technique

Multi-layered electroless Ni–P coatings on powder-sintered Nd–Fe–B permanent magnet

Corrosion protection of Nd–Fe–B magnets by bismaleimide coating

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Magnetic Properties Hard-Soft SmCo<sub>5</sub>-FeNi and SmCo<sub>5</sub>-FeCo Composites Prepared by Electroless Coating Technique

Magnetic Properties Hard-Soft SmCo<sub>5</sub>-FeNi and SmCo<sub>5</sub>-FeCo Composites Prepared by Electroless Coating Technique