Parameter influence and corrosion resistance mechanism of Ni coatings under pulse electroplating

The Ni plating was prepared on the surface of the NdFeB magnet under a pulse current, and the pulse parameters were optimized by one-variate test in turn. The results showed that the Ni plating was of the least corrosion resistance tendency and corrosion rate, and the optimal electrochemical corrosion resistance at the duty ratio of 60%, frequency of 1 000 Hz and current density of 6 A/dm². It was found that in the microstructure of the plating that the Ni particles were of more uniform size and the plating of smoothing surface so that the overall quality of Ni plating was promoted, and the corrosion resistance was improved as well. Under the same static corrosion condition, it was also found that aggregated corrosion products were generated on the surface of Ni plating when duty ratio and frequency were optimized, which showed rather serious stress corrosion. Regulating the current density in the process of plating could reduce the residual stress of the plating and avoid stress corrosion, and accordingly improve the corrosion resistance of Ni plating.