Corrosion and protection of rare earth magnets: patent review

Permanent magnets based on rare earths have become very important because they are used in products with high added value such as electric or hybrid motor vehicles and wind generators. This article aims at presenting a bibliographical review on patents related to corrosion and corrosion protection of (Nd, Pr)-Fe-B alloys. China and Japan are leading the patent records related to corrosion of rare-earth magnets and coatings of these magnets. The epoxy-resin-based protective coating presents the largest number of patents. The patents were deposited mainly by manufacturers or by large permanent-magnet consumers while research institutions and universities are in the background. During the 1990’s, metallic finishes of Ni, Zn (Zn and its alloys) and Cr, applied by electrodeposition, have been used as protective coating of permanent magnets. Epoxy resin based-coatings preceded with phosphating and sealing processes have also been employed. In early 2000, a vapor deposition technique was used to apply on protective metal and organic layers. The most recent patents are directed to develop a magnetic alloy with an addition of elements such as Ga, Al, Dy, Ho, Ni and Co for an alloy with greater resistance to corrosion.

SANTOS, Célia Aparecida Lino dos; TUKOFF-GUIMARÃES, Yuri; PANOSSIAN, Zehbour. Corrosão e proteção de imãs de terras raras: revisão de patentes. Revista IPT Tecnologia e Inovação, v.1, n.5, p. 41-54, ago., 2017.

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