Corrosion and corrosion protection of RE-Fe-B magnets

Journal Article · Sun Jan 01 00:00:00 EST 1989 · Journal of Materials Engineering; (USA)

DOI:https://doi.org/10.1007/BF02833759· OSTI ID:5125427

Kim, A S ^[1]

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1. IG Technologies Inc., Valparaiso, IN (US)

The corrosion behavior of Nd-Fe-B magnets is addressed in this paper. It varies depending on the alloy composition, surface condition, and corrosion environment and temperature. The kinetics of corrosion of Nd-Fe-B magnets in deionized water at room temperature are usually a gradual weight decrease, while those in an autoclave environment are generally a two-step weight change: first, an incubation step; second, linear weight loss. The corrosion products in deionized water are mainly Fe (OH)/sub 2/, while those in an autoclave are mainly Nd(OH)/sub 3/. Magnets surface treated with H/sub 2/CrO/sub 4/, HF, H/sub 3/PO/sub 4/, or their combinations exhibit a significant improvement in corrosion resistance compared with untreated magnets. The mechanism of corrosion protection for Nd-Fe-B magnets by surface treatment with H/sub 2/CrO/sub 4/ is believed to be removal of the nucleation site for corrosion by chromic acid etch, and formation of a protective film on the surface by chromate conversion. The combination of surface treatment and alloying with elements such as Dy will further improve the corrosion resistance of the magnet.

• OSTI ID: 5125427
• Journal Information: Journal of Materials Engineering; (USA), Vol. 11:1; ISSN 0931-7058
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BORON ALLOYS
MAGNETIC PROPERTIES
IRON ALLOYS
NEODYMIUM ALLOYS
PERMANENT MAGNETS
CORROSION PROTECTION
CHEMICAL COMPOSITION
CHEMICAL REACTION KINETICS
CHROMATES
CORROSION INHIBITORS
CORROSIVE EFFECTS
DYSPROSIUM ADDITIONS
ALLOYS
CHROMIUM COMPOUNDS
DYSPROSIUM ALLOYS
KINETICS
MAGNETS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH ADDITIONS
RARE EARTH ALLOYS
REACTION KINETICS
TRANSITION ELEMENT COMPOUNDS
360104* - Metals & Alloys- Physical Properties
360105 - Metals & Alloys- Corrosion & Erosion
400201 - Chemical & Physicochemical Properties