Influence of the electroplating pretreatment on corrosion mechanism of NdFeB magnets

The electroplating pretreatment of NdFeB magnets was simulated in this study, and the effect of the pickling process on element, matrix morphology and texture was discussed. The results showed that in the ordinary circumstance the acid solution concentration should be below 4 mol/L and the pickling time was within 120 s. However the concentration was lower than 1 mol/L and the time was about 30 s in the ultrasonic environment. The precoating technology sequentially was studied. The results revealed that there were two main reactions of the corrosion and displacement in the precoating process, and these two reactions were more obvious in the grain boundary. The electrochemical analysis illustrated that the corrosion and displacement reactions were affected obviously by the current density and the precoating solution temperature, usually the current density was controlled about 0.3 A/dm2, and the temperature was about 318 K in the precoating process.

Graphical AbstractMorphology of NdFeB magnets after precoating for 30 minFigure optionsDownload full-size imageDownload as PowerPoint slide