Rare earth passivation and corrosion resistance of zinc coated NdFeB magnets

Chen, Jing; Yang, Hongyi; Xu, Guangqing; Zhang, Pengjie; Lv, Jun; Sun, Wei; Li, Bingshan; Huang, Jun; Wang, Dongmei; Shu, Xiaoyan; Wu, Yucheng

doi:10.1016/j.jre.2020.11.012

Cited by 21 publications

(5 citation statements)

References 31 publications

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“…Alloying with elements such as Al, Co, Cr, Ga, Nb, Pb, P, Sn, Ti, Zr, Ho or Ce can improve the corrosion resistance of the magnets [ 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Common metallic coatings are Zn [ 22 , 23 , 24 ], Ni [ 25 , 26 , 27 ], Ni/Cu/Ni [ 28 , 29 ], or less commonly, Sn [ 10 ], Al [ 30 , 31 , 32 ] and Zn-Ni [ 33 ]. Metallic coatings are often deposited by electroplating [ 24 , 26 ].…”

Section: Methodsmentioning

confidence: 99%

Processability and Separability of Commercial Anti-Corrosion Coatings Produced by In Situ Hydrogen-Processing of Magnetic Scrap (HPMS) Recycling of NdFeB

Grau,

Fleissner,

Kobe

et al. 2024

Materials

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The recycling of NdFeB magnets is necessary to ensure a reliable and ethical supply of rare earth elements as critical raw materials. This has been recognized internationally, prompting the implementation of large-scale legislative measured aimed at its resolution; for example, an ambitious recycling quote has been established in the Critical Raw Materials Act Successful recycling in sufficient quantities is challenged by product designs that do not allow the extraction and recycling of these high-performance permanent magnets without excessive effort and cost. This is particularly true for smaller motors using NdFeB magnets. Therefore, methods of recycling such arrangements with little or no dismantling are being researched. They are tested for the hydrogen-processing of magnetic scrap (HPMS) method, a short-loop mechanical recycling process. As contamination of the recycled material with residues of anti-corrosion coatings, adhesives, etc., may lead to downcycling, the separability of such residues from bulk magnets and magnet powder is explored. It is found that the hydrogen permeability, expansion volume, and the chosen coating affect the viable preparation and separation methods as recyclability-relevant design features.

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Section: Methodsmentioning

confidence: 99%

Processability and Separability of Commercial Anti-Corrosion Coatings Produced by In Situ Hydrogen-Processing of Magnetic Scrap (HPMS) Recycling of NdFeB

Grau,

Fleissner,

Kobe

et al. 2024

Materials

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“…Rare earth oxides are capable of providing anti-corrosion activity under harsh conditions by shielding the cathode region of the metal surface [13][14][15] . Amongst the numerous rare earth oxides, cerium-based compounds exert the greatest corrosion resistance performance by forming a Ce-containing passive lm that can suppresses the cathode reaction.…”

Section: Introductionmentioning

confidence: 99%

Preparation of CeO 2 -PPy nanocomposites to improve the corrosion resistance of epoxy resin coatings

Feng

Liu

et al. 2023

Preprint

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Here, CeO2 was used as the sole oxidant for pyrrole polymerization via in-situ chemical oxidation, and polypyrrole (PPy) was grown on the CeO2 surface to form CeO2-PPy nanocomposites. The morphology of CeO2-PPy nanocomposites was observed using SEM. The electrochemical corrosion behavior of the coatings in 3.5 wt% NaCl solution was investigated through electrochemical impedance spectroscopy (EIS) measurements. After 40 days of immersion, the coating with CeO2-PPy nanocomposite fillers exhibited outstanding anti-corrosion performance, and the |Z|0.01 Hz value exceeded 108 Ω·cm2, which was one order of magnitude higher than of the pure epoxy coating. The enhanced corrosion protection was attributed to the complex passive film produced by the synergistic effect of PPy and cerium(Ⅲ) ions. The results showed that CeO2-PPy nanocomposites can be used as fillers for the corrosion protection of steel substrates.

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“…According to our knowledge, many attempts have been made to improve the corrosion resistance of NdFeB magnets, such as alloy addition and surface treatment [ 7 , 8 , 9 ]. Compared with alloy addition, surface treatments, such as monometal [ 10 , 11 , 12 , 13 , 14 ], nonmetal [ 15 , 16 ], alloy [ 17 , 18 , 19 , 20 , 21 ] or composite [ 22 , 23 , 24 , 25 , 26 , 27 ] coatings, can effectively improve the corrosion resistance of NdFeB magnets without reducing their magnetic fields. However, in all of these coatings and their preparation methods, electrodeposited metal coatings are still commonly applied in industry to this day.…”

Section: Introductionmentioning

confidence: 99%

“…Compared to other surface treatments, they are suitable for large-scale production due to their lower cost and easier control. Among them, electroplating zinc coatings account for a large part of the industry [ 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

Morphology and Anti-Corrosive Performance of Cr(III) Passivated Zn–Fe Alloy Coating on NdFeB Substrate

Zhou

Chen

et al. 2022

Materials

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In this study, low-iron Zn–Fe alloy coatings and pure Zn coatings, with or without trivalent chromium passivation treatment, were electrodeposited onto a sintered NdFeB magnet from a weak acid chloride bath. The surface morphology and structure of the coatings were then examined using the X-ray diffraction, a scanning electron microscope and 3D white-light interfering surface analysis. Meanwhile, the electrodeposition behavior and anti-corrosive properties of the coatings were investigated using cyclic voltammetry, potentiodynamic polarization, electrochemical impedance spectroscopy, and natural salt spray tests. The results indicate that a passivated Zn–Fe alloy coating with a 0.9 wt.% Fe content provided much better corrosion resistance than a pure Zn coating and could provide both anodic protection and physical barrier function in the NdFeB substrates. The Fe element in Zn–Fe alloy coating was predominantly in solid solution in η-phase and small amounts in elemental form, which was beneficial to acquire a compact coating and passivation film. Finally, the passivated Zn–Fe alloy coating withstood 210 h against a neutral 3.5 wt.% NaCl salt spray without any white rust, which was 3–4 times longer than the pure Zn coating.

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Rare earth passivation and corrosion resistance of zinc coated NdFeB magnets

Cited by 21 publications

References 31 publications

Processability and Separability of Commercial Anti-Corrosion Coatings Produced by In Situ Hydrogen-Processing of Magnetic Scrap (HPMS) Recycling of NdFeB

Processability and Separability of Commercial Anti-Corrosion Coatings Produced by In Situ Hydrogen-Processing of Magnetic Scrap (HPMS) Recycling of NdFeB

Preparation of CeO 2 -PPy nanocomposites to improve the corrosion resistance of epoxy resin coatings

Morphology and Anti-Corrosive Performance of Cr(III) Passivated Zn–Fe Alloy Coating on NdFeB Substrate

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