钕对镁合金电偶腐蚀电流密度及分布的影响

气体保护条件下,通过向镁合金熔体中加入Mg-Nd中间合金的方法制备出不同稀土Nd含量的改性镁合金Mg-9Al-1Zn-xNd(AZ91Nd).采用电偶腐蚀、腐蚀电化学、X射线光电子谱(XPS)等方法研究了AZ91Nd镁合金在电偶腐蚀过程中的电流密度和分布的变化规律.电化学分析表明,在腐蚀过程中,镁合金腐蚀产物膜中含有一定量的Nd2O3,提高了AZ91Nd镁合金的自腐蚀电位和极化阻抗.腐蚀实验表明,Nd能够降低镁合金电偶腐蚀电流密度,促进电偶腐蚀电流在阳极表面均匀分布,抑制了局部腐蚀,提高了镁合金的抗电偶腐蚀性能.AZ91Nd耐蚀性提高的主要原因在于:Nd2O3提高了腐蚀产物膜的致密性导致合金的腐蚀电位和极化阻抗增加.

Influence of Neodymium on Density and Distribution of Galvanic Corrosion Currents in Magnesium Alloys

A series of Mg-9Al-1Zn-xNd(AZ91Nd) was prepared by adding Mg-Nd master alloy into AZ91 under the protection of CO2+SF6.The density and distribution of galvanic corrosion currents of the AZ91Nd magnesium alloys were investigated by galvanic corrosion tests,electrochemical analysis and X-ray photoelectron spectroscopy(XPS).The XPS results indicated that Nd was incorporated into corrosion film in the form of Nd2O3 during the corrosion.The electrochemical analysis indicated that the addition of Nd increased the corrosion potential and impedance.The corrosion tests indicated that Nd could decrease the current density,improve the uniformity of the current distribution.As a result,the local corrosion of AZ91Nd was effectively restrained and the galvanic corrosion resistance was enhanced.The enhancement of the galvanic corrosion resistance was mainly attributed to the increase of corrosion potential and impedance resulting from the incorporation of Nd2O3 in the corrosion film.