氢氧化钠浓度对镁合金阳极氧化的影响

采用电压-时间曲线、全浸腐蚀实验、极化曲线法、X射线衍射法(XRD)、扫描电镜(SEM)和能量色散谱仪(EDS)等方法研究了AZ91D镁合金在含不同浓度氢氧化钠溶液中的阳极氧化行为和膜层的成分、结构。结果表明,在本研究给定工艺中,AZ91D镁合金的阳极氧化过程可分为三个阶段:电火花出现之前的致密层生成阶段,少量小电火花出现的多孔层生成阶段,出现较大电火花的多孔膜层稳定生长阶段。阳极氧化过程中,随着NaOH浓度的升高,出现电火花的时间缩短,出现电火花的电压值降低,阳极氧化膜表面的颗粒变小、孔隙率减小,膜层厚度减小;阳极氧化膜的主要组成是MgO,并含有少量的Mg3B2O6;NaOH浓度对阳极氧化膜耐蚀性影响较大,当NaOH浓度为40g/L时,膜层的耐蚀性能最好。

Effects of Concentration of Sodium Hydrate on Anodizing for Magnesium Alloys

The anodizing of AZ91D Mg alloys in the solution of different concentration of NaOH was investigated by ways of voltage-time curve, immersion corrosion experiment, polarization curve, XRD, SEM, EDS and XPS respectively. The results show that anodizing process can be divided into three stages:formation of dense film before sparking, formed porous film accompanied with a bit of small spark, and porous film stable growth along with bigger spark. With increasing concentration of NaOH in the solution of the anodizing, the time and voltage of spark formation decrease and particle, porosity, thickness of anodic oxide film become smaller. The anodic oxide film contains MgO and a small quantity of Mg_3B_2O_6. The concentration of NaOH has great effects on corrosion resistance of anodic oxide film. The anodic oxide film has best corrosion resistance when the concentration of NaOH in the solution of the anodizing is 40g/L.