Influence of Transition Layer on Corrosion Resistance of Evaporated Al Coating on NdFeB Magnets

LIN Song-sheng, SU Yi-fan, SONG Ke-wei, HU Fang, SHI Qian, HOU Hui-jun, WEI Chun-bei, LI Hong, DAI Ming-jiang

Surface Technology ›› 2017, Vol. 46 ›› Issue (12) : 218-224.

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Surface Technology ›› 2017, Vol. 46 ›› Issue (12) : 218-224. DOI: 10.16490/j.cnki.issn.1001-3660.2017.12.034
Surface Failure and Protection

Influence of Transition Layer on Corrosion Resistance of Evaporated Al Coating on NdFeB Magnets

  • LIN Song-sheng, SU Yi-fan, SONG Ke-wei, HU Fang, SHI Qian, HOU Hui-jun, WEI Chun-bei, LI Hong, DAI Ming-jiang
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Abstract

The work aims to improve bonding strength and corrosion resistance of Al protective coatings on NdFeB magnets. Al transition layer was deposited on NdFeB magnets by magnetron sputtering, then the transition layer was bombarded at high bias voltage, Al protective layer was deposited by applying ion-assisted evaporation technique. Surface and cross-section morphology of the Al coatings were observed with SEM, corrosion resistance was tested by using electrochemical workstation and salt spray test, and adhesion to substrate was evaluated by performing tensile test. As magnetron sputtering target current increased from 10 A to 25 A, self-corrosion voltage of the as-deposited Al coatings decreased from -0.7367 V to -0.9075 V, and neutral salt spray corrosion resistance decreased as well. Provided that surface ion-assisted evaporated Al protective coatings were prepared in the same process, salt spray corrosion resistance time of Al protective coatings prepared at magnetron sputtering target current of 25 A with a 100 nm and 500 nm Al transition layer was 48 hours and 36 hours, respectively, the corrosion resistance of the coatings with transition layer was inferior to pure evaporated Al coating without transition layer (72h); salt spray corrosion resistance time of Al protective coatings prepared at magnetron sputtering target current of 15 A with a 100 nm and 500 nm Al transition layer was 96 hours and 103 hours, respectively, the corrosion resistance of the coatings with transition layer was superior to pure evaporated Al coating without transition layer. Bonding strength of Al protective coatings adopting transition layer technology was over 40 MPa, the coatings are firmly bonded with the NdFeB substrate. Bonding between Al coating and the NdFeB substrate can be improved by adopting transition layer technology, and corrosion resistance of ion-assisted evaporated Al coating can be improved by applying proper transition layer technology.

Key words

NdFeB; transition layer; ion assisted evaporation; Al coatings; corrosion resistance

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LIN Song-sheng, SU Yi-fan, SONG Ke-wei, HU Fang, SHI Qian, HOU Hui-jun, WEI Chun-bei, LI Hong, DAI Ming-jiang. Influence of Transition Layer on Corrosion Resistance of Evaporated Al Coating on NdFeB Magnets[J]. Surface Technology. 2017, 46(12): 218-224

Funding

Supported by the Science and Technology Plan Projects of Guangdong Province (2013B090500115) and Platform Construction Project of Guangdong Academy of Sciences (2016GDASPT-0206, 2016GDASPT-0317)
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