Corrosion Behavior of Surface Modified NdFeB Permanent Magnet in Dilute Chloride Environments
By Chitrada, Kalyan; Raja, Krishnan S.; Pesic, Batric & Charit, Indrajit
Published in Electrochimica Acta
2014
Abstract
Nanoporous oxide layer was formed on the NdFeB permanent magnets by a simple anodization process in fluoride containing ethylene glycol at 50 V for 15 minutes. The electrochemical polarization behavior of the commercial permanent magnetic material was evaluated in 0.1 M NaH2PO4 solution (pH: 4.75) containing 0–0.017 M of chloride at room temperature. The material was evaluated in magnetized and demagnetized condition with different surface preparation conditions such as: Ni-Cu-Ni coated, uncoated (bare), and anodized. The nickel coated magnetic sample showed reasonable pitting corrosion resistance up to 0.0017 M chloride addition. The uncoated samples showed passivity in chloride free phosphate solution. Chloride additions caused pitting and the pitting protection potential was equal to the corrosion potential with 0.0017 M chloride addition. Demagnetization did not alter the electrochemical polarization. However, the passive film formed on the magnetic sample showed higher charge carrier density than the film formed on the demagnetized sample.