Abstract Al coated NdFeB magnets were prepared by plasma-assisted-physical-vapor-deposition (PA-PVD) method for enhancing the corrosion resistance. Morphologies and structures were characterized by an X-ray diffractometer and a scanning electron microscope. Corrosion behaviors of the samples with different bias voltages were studied by electrochemical methods and neutral salt spray test respectively. The bias voltage during the deposition process was optimized according to the coating structures and corrosion resistances. The density and flatness of Al coating increase with increasing the bias voltage, and at the same time the thickness decreases. The coating density and thickness turn to be stable when bias voltage is 1800 V. Also, the corrosion behaviors of PA-PVD Al coatings in different media, such as NaOH, HNO3 and NaCl solutions, were studied. The self-corrosion potentials (Ecorr) of PA-PVD Al coatings almost keep constant in NaOH and HNO3 solutions with different concentrations. However, the self-corrosion current densities (Jcorr) decrease with the concentrations. The Ecorr shifts to negative potential and the Jcorr decreases gradually when increasing the concentration of NaCl solution. The corrosion mechanisms of Al coatings are discussed based on the corrosion behaviors in different media.

中文翻译：

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偏压对PA-PVD Al包覆钕铁硼磁体涂层结构及防腐性能的影响

摘要 采用等离子体辅助物理气相沉积（PA-PVD）方法制备了Al涂层NdFeB磁体，以提高其抗腐蚀性能。通过 X 射线衍射仪和扫描电子显微镜表征形态和结构。分别采用电化学方法和中性盐雾试验研究了不同偏压下样品的腐蚀行为。沉积过程中的偏置电压根据涂层结构和耐腐蚀性进行优化。Al涂层的密度和平整度随着偏置电压的增加而增加，同时厚度减小。当偏置电压为 1800 V 时，涂层密度和厚度趋于稳定。此外，PA-PVD Al 涂层在不同介质（如 NaOH、HNO3 和 NaCl 溶液）中的腐蚀行为，被研究。PA-PVD Al涂层的自腐蚀电位（Ecorr）在不同浓度的NaOH和HNO3溶液中几乎保持恒定。然而，自腐蚀电流密度（Jcorr）随着浓度的增加而降低。随着 NaCl 溶液浓度的增加，Ecorr 向负电位移动，Jcorr 逐渐减小。基于不同介质中的腐蚀行为讨论了铝涂层的腐蚀机理。