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<p>NdFeB permanent magnets, primarily composed of rare earth elements (REEs), are highly susceptible to oxidation, which necessitates the application of a protective nickel coating. However, this coating hinders efficient REE recovery from waste magnets. To address this, this study presents an innovative automated recycling approach that improves impurity removal while minimizing environmental impact. Using a self-designed crushing and separation machine, the automated process achieves a 99.4% powder recovery rate per 100 kg batch, enhancing recycling efficiency. Recycled magnets processed via automation demonstrate remanence (<i>B</i><sub>r</sub>) of 13.78 kG, intrinsic coercivity (<sub>i</sub><i>H</i><sub>c</sub>) of 16.39 kOe, and maximum magnetic flux density ((<i>BH</i>)<sub>max</sub>) of 44.87 MGOe, closely matching manually processed magnets and meeting the N48H-grade standard. Electrochemical analysis further shows superior corrosion resistance, with a corrosion current density of 6.4329 × 10⁻<sup>5</sup> A/cm<sup>2</sup>, outperforming both manually processed magnets (7.5343 × 10⁻<sup>5</sup> A/cm<sup>2</sup>) and virgin waste magnets (2.6 × 10⁻<sup>4</sup> A/cm<sup>2</sup>). This study also examines the impact of nickel removal on magnetic performance and corrosion resistance, offering insights for optimizing the purification process. A comparison with traditional methods highlights the benefits of automation in impurity reduction and material recovery. The findings confirm that maintaining nickel levels below 900 ppm preserves magnetic properties and enhances durability, establishing a commercially viable “magnet-to-magnet” NdFeB recycling pathway.</p>

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Investigation of nickel coating removal and the influence of nickel impurities on the recovery of NdFeB permanent magnets from end-of-life magnet scrap

  • 期刊论文

  • 发表日期：

    2025年4月10日

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  • Chih-Chieh Mo,
  • Shih-Fu Ou,
  • Ching-Chien Huang

摘要

NdFeB permanent magnets, primarily composed of rare earth elements (REEs), are highly susceptible to oxidation, which necessitates the application of a protective nickel coating. However, this coating hinders efficient REE recovery from waste magnets. To address this, this study presents an innovative automated recycling approach that improves impurity removal while minimizing environmental impact. Using a self-designed crushing and separation machine, the automated process achieves a 99.4% powder recovery rate per 100 kg batch, enhancing recycling efficiency. Recycled magnets processed via automation demonstrate remanence (Br) of 13.78 kG, intrinsic coercivity (iHc) of 16.39 kOe, and maximum magnetic flux density ((BH)max) of 44.87 MGOe, closely matching manually processed magnets and meeting the N48H-grade standard. Electrochemical analysis further shows superior corrosion resistance, with a corrosion current density of 6.4329 × 10⁻5 A/cm2, outperforming both manually processed magnets (7.5343 × 10⁻5 A/cm2) and virgin waste magnets (2.6 × 10⁻4 A/cm2). This study also examines the impact of nickel removal on magnetic performance and corrosion resistance, offering insights for optimizing the purification process. A comparison with traditional methods highlights the benefits of automation in impurity reduction and material recovery. The findings confirm that maintaining nickel levels below 900 ppm preserves magnetic properties and enhances durability, establishing a commercially viable “magnet-to-magnet” NdFeB recycling pathway.