脉冲电镀Ni镀层参数影响及耐腐蚀机理

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

  • 摘要: 用脉冲电流在钕铁硼磁体表面制备Ni镀层;并通过单因素试验依次对脉冲参数进行优化。实验发现当占空比为60%、频率为1 000 Hz、电流密度为6 A/dm2时,Ni镀层的耐腐蚀倾向和腐蚀速率最小,Ni镀层耐电化学腐蚀性能较优。观察镀层表面的微观结构发现镀层表面Ni颗粒尺寸更加均匀,镀层表面平整度更高,因此镀层的综合质量更高,改善了镀层的耐腐蚀性能。对相同静态腐蚀条件下Ni镀层腐蚀形貌观察发现,占空比和频率优化后的Ni镀层表面均生成团聚状的腐蚀产物,出现应力腐蚀现象,腐蚀较为严重。调控电镀过程中的电流密度能够减少镀层的残余应力,避免出现应力腐蚀现象,从而提升镍镀层的耐腐蚀性能。

     

    Abstract: 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.

     

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