分别以La(NO3)3·6H2O为主盐、H2O2为氧化剂和NaF为促进剂，对钢铁基热浸Zn–2%(质量分数)Al合金镀层进行化学转化。通过正交试验研究了不同因素对转化膜耐蚀性的影响，得到镧盐转化的最佳工艺条件为：La(NO3)3·6H2O 10~15 g/L，H2O210 mL/L， NaF 0.5 g/L，温度70°C，时间10~30 min。成膜温度和处理时间对转化膜耐蚀性的影响较大，NaF的加入有利于成膜。在最佳工艺条件下得到的镧盐转化膜经过3个周期中性盐雾试验后的白锈面积分数为15%，耐蚀性明显优于未钝化试样。
Hot-dip galvanized Zn–2wt% Al alloy coating on steel substrate was chemically conversed in a solution with La(NO3)3·6H2O as main salt, H2O2 as oxidant, and NaF as promoter. The effects of different factors on corrosion resistance of the conversion coating were studied through orthogonal test. The optimal range of different parameters for lanthanum conversion are as follows: La(NO3)3·6H2O10-15g/L, H2O210mL/L, NaF0.5g/L, temperature 70 °C, and time10-30 min. Both film forming temperature and time have great effects on corrosion resistance of the conversion coating. The addition of NaF is beneficial to film formation. The area fraction of white rust on lanthanum conversion coating obtained under the optimal conditions is 15% after neutral salt spray test for 3 periods, showing better corrosion resistance than that of the unpassivated Zn–2wt%Al alloy coating.
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