Effect of DyF3 on the corrosion behavior of hot‐pressed Nd–Fe–B permanent magnets. Issue 2 (10th December 2013)

• Record Type: Journal Article
• Authors: Sueptitz, R.; Sawatzki, S.; Moore, M.; Uhlemann, M.; Gutfleisch, O.; Gebert, A.
• Is Part Of: Materials and corrosion. Volume 66:Issue 2(2015:Feb.)
• Page Start: 152
• Page End: 157
• Publication Date: 2013-12-10
• Subjects: Materials -- Periodicals; Metals -- Periodicals; Corrosion and anti-corrosives -- Periodicals; 620.1122305
• DOI: 10.1002/maco.201307303
• Languages: English
• ISSNs: 0947-5117

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="maco201307303-sec-0001" sec-type="section"> <p>The grain boundary diffusion process (GBDP) with DyF₃ is a promising method to obtain excellent magnetic properties in Nd–Fe–B permanent magnets. Compared to conventionally prepared (Dy, Nd)–Fe–B magnets the overall content of the precious heavy rare earth Dy is reduced. Thus, the GBDP with DyF₃ is highly attractive to cut down costs and save resources. However, it is not well known how the addition of DyF₃ affects the corrosion resistance of Nd–Fe–B permanent magnets. In this work, the anodic polarization behavior of hot‐pressed Nd–Fe–B magnets with and without DyF₃ additions was investigated in electrolytes of different pH values. The results were compared with measurements on a commercially sintered Nd–Fe–B permanent magnet. In the polarization studies the only observed significant impact of DyF₃ additions is an increased passive current density in alkaline media. The pitting susceptibility in NaOH solutions containing chloride ions is not affected by DyF₃. Also in contrast to expectations, first free corrosion studies indicated no significant impact of the DyF₃ additions on the dissolution rate.</p> </sec> </abstract>