Author/Authors :
Bala، نويسنده , , H. and Trepak، نويسنده , , N.M. and Szymura، نويسنده , , S. and Lukin، نويسنده , , A.A. and Gaudyn، نويسنده , , V.A. and Isaicheva، نويسنده , , L.A. and Paw?owska، نويسنده , , G. and Ilina، نويسنده , , L.A.، نويسنده ,
Abstract :
The use of protective zinc phosphate top coatings to protect Nd–Fe–B type permanent magnets against corrosion is discussed. The progress of the phosphatisation process has been tested by simultaneous measurement of pH near surface, corrosion potential, substrate mass loss and phosphate coating mass gain. The corrosion behaviour of the magnet in phosphate solution was analyzed by the anodic polarization technique and the general resistance of the magnet to corrosion was evaluated by the Akimov drop test. It is shown that immersion of the magnet in the acidified (pH=2) phosphating solution containing Zn(II), nitrate and fluoride ions resulted in the formation of well adhered, thin and tight hopeite layers, causing prolonged corrosion resistance of the magnet.
