镁合金在大气环境中电偶腐蚀行为及规律的研究

Research on Atmospheric Galvanic Corrosion Evaluation of Magnesium Alloy

摘要:

在北京大气环境下，研究AM60镁合金和不同金属材料（碳钢、不锈钢、黄铜和铝合金）偶接的电偶腐蚀行为规律。研究表明，镁合金作为阳极发生不同程度的电偶腐蚀，通过1a的北京大气环境下的暴露试验后，AM60镁合金的电偶腐蚀效应由强到弱的顺序为：碳钢、黄铜、不锈钢和铝合金，其中镁合金与LY12铝合金偶接的电偶腐蚀效应最小。通过与其它地区室外暴晒的镁合金电偶腐蚀效应的对比，表明环境因素影响着镁合金的电偶腐蚀效应。同时阴极材料、试验时间、试样尺寸（偶接面积）和试验环境都会对镁合金电偶腐蚀效应产生影响。经1a曝晒的AM60镁合金形成了具有保护性的腐蚀产物层阻碍了腐蚀发展。北京地区高自然降尘量导致金属表面湿润时间加大，从而加速了AM60镁合金的电偶腐蚀。采用XRD方法分析表面的腐蚀产物，用金相显微镜和扫描电镜（SEM）观察试样腐蚀后的表面形貌特征和腐蚀产物的结构，并用与之相连的能谱仪分析腐蚀产物中的元素组成。

Abstract:

This paper presents the galvanic corrosion behaviors of AM60 magnesium alloy coupled with variable materials(carbon steel,stainless steel,brass and aluminum alloy) in the outdoor atmosphere of Beijing.The correlations among mass variation,galvanic effect and atmospheric factors for AM60 magnesium alloy coupons were investigated.Surface morphologies were observed by scanning electron microscopy(SEM),and X-ray diffraction(XRD) was used to analyze the crystal corrosion products.The results showed that the AM60 magnesium alloy acted as anodic material when it coupled with tested metals.The arrangement order of galvanic effect from strong to little is carbon steel,brass,stainless steel and aluminum alloy after 12 months exposure in Beijing atmosphere.The atmospheric galvanic effect of magnesium alloys coupled with aluminum alloy is the least among the tested coupled alloys during any testing periods because the effective potential difference of the cathode(AM60) and anode(aluminum alloy) is the least for all of tested coupled alloys.The atmospheric galvanic effects in Beijing compared with other cities indicate that atmospheric environment is most important factor.The atmospheric galvanic effects for magnesium alloys are affected by cathode alloy,testing time,sample acreage and environment condition.And no intact and protective corroded products layer was formed to prevent further corrosion after 1 year exposure.The edge of AM60 coupon suffered harsh galvanic corrosion,which was limited by the existing of thin-film on the coupon surface.The high dust precipitation of Beijing could prolong the time of wetness on metal surface.So,the atmospheric corrosion of AM60 magnesium alloy coupled with different metals could be accelerated.