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通过尿素水解法在AZ31镁合金表面原位合成纳米尺度的层状双金属氢氧化物(水滑石)转化膜,并提出成膜机理。首先,溶解的Mg2+离子沉积形成含有MgC O3和Mg5(CO3)4(OH)2·4H2O的前驱体膜;然后,前驱体膜在碱性条件下转化为高结晶的Mg(OH)2;最后,Mg(OH)2中的Mg2+离子被Al3+离子取代,Mg(OH)2转化为更稳定的水滑石层状结构,同时层间OH-与溶液中的CO2-3发生离子交换,因此形成水滑石(Mg6Al2(OH)16CO3·4H2O)膜。结果表明,以互锁的片状纳米结构和离子交换性能为特征的水滑石膜可以有效提高AZ31镁合金的耐蚀性。
The nanometer scale layered bimetallic hydroxide (hydrotalcite) conversion coating was synthesized on the surface of AZ31 magnesium alloy by urea hydrolysis, and the film formation mechanism was proposed. First, the dissolved Mg2 + ions are deposited to form a precursor film containing MgC03 and Mg5 (CO3) 4 (OH) 2.4H2O; the precursor film is then converted to highly crystalline Mg (OH) 2 under alkaline conditions; finally , Mg2 + ions in Mg (OH) 2 are replaced by Al3 + ions and Mg (OH) 2 is transformed into a more stable layered structure of hydrotalcite, while interlayer OH- ion-exchanges with CO2-3 in the solution, thus forming water Talc (Mg6Al2 (OH) 16CO3.4H2O) film. The results show that the hydrotalcite films, which are characterized by the interlocking flake nanostructures and ion exchange performance, can effectively improve the corrosion resistance of AZ31 magnesium alloy.