添加RE和Mn元素对Mg-9Al合金耐蚀性的影响

Effect of elemental RE and Mn on corrosion resistance of Mg-9Al Alloy

采用腐蚀失重试验、析氢试验及动电位极化曲线扫描测试手段,研究RE和Mn元素对Mg-9Al镁合金在Mg(OH)2饱和的3.5%NaCl(质量分数)溶液中腐蚀性能的影响,同时利用电子探针(EPMA)研究它们的微结构和组织形貌。研究结果表明:Mn元素的加入能使合金中形成许多易氧化的富Mn析出相,将有害的Fe元素杂质结合到富Mn析出相中,从而显著抑制合金的阴极过程,减少氢的析出,明显提高合金的耐蚀性。在Mg-9Al-RE镁合金中,RE与Mn协同作用形成MgAlMnRE相,降低合金中阴极的阴极活性,进一步提高合金的耐蚀性。

Effects of Mn and RE addition on corrosion behavior of Mg-9Al alloys were studied in 3.5% NaCl solution with Mg（OH）2 saturated at 25℃ by measuring the magnesium dissolution rate and the hydrogen evolution rate, simultaneously measuring electrochemical polarization curves. The microstructure of the alloys was examined by electron probe X-ray microanalyzer. The resuits obtained by general analysis indicated that Mn can trap the deleterious elemental Fe, which can decrease the activity of Fe cathode. The passivity area with Mn rich phase can restrain the hydrogen evolution reaction. So the corrosion resistance can be generally improved by adding higher Mn in the Mg-9Al alloys. The RE addition in the Mg-9Al alloys can form the MgAlRE phase, which can decrease the cathode activity, too. Moreover, the combinative effect of Mn and RE addition can further enhance the corrosion resistance of Mg-9Al alloys.