不同稀土元素对镁合金钼酸盐转化膜耐蚀性的影响

Effect of Different Rare Earth Elements on Corrosion Resistance of Molybdate Conversion Coatings on Magnesium Alloy

研究了硝酸铈、氧化钕和硝酸镧对镁合金钼酸盐转化膜耐蚀性的影响。通过单因素试验,得出添加氧化钕的镁合金钼酸盐化学转化的最佳配方为:钼酸铵25g/L,硝酸钠1.5g/L,硝酸锰1.0g/L,柠檬酸1.5g/L,氧化钕0.4g/L,pH值5,温度60℃,时间30min。最佳配方下得到的膜层均匀平滑,结晶颗粒细小、分布均匀、大小均等。添加氧化钕的钼酸盐转化膜的自腐蚀电流密度最低,耐蚀性最好。

The effects of cerium nitrate,neodymium oxide and lanthanum nitrate on the corrosion resistance of molybdate conversion coatings on magnesium alloy were studied.Through the single factor experiment,the optimum formula of molybdate chemical conversion with neodymium oxide for magnesium alloy was determined as follows:ammonium molybdate 25 g/L,sodium nitrate 1.5 g/L,manganese nitrate 1.0 g/L,citric acid 1.5 g/L,neodymium oxide 0.4 g/L,pH value 5,temperature 60℃,time 30 min.The coating obtained with optimum formula was uniform and smooth,the grains were fine,well-distributed and uniform in size.The molybdate conversion coating obtained with neodymium oxide exhibits the best corrosion resistance,its self-corrosion current density was the lowest.