Corrosion and corrosion protection of RE-Fe-B magnets

Journal Article · Sun Jan 01 04:00:00 EST 1989 · Journal of Materials Engineering; (USA)

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

Kim, A S ^[1]

---

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

Related Subjects

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