以锌系磷酸盐化学转化膜为研究体系,采用SEM,XRD分析方法及检测手段,研究乙醇胺(MEA)添加剂及其浓度对AZ91D镁合金锌系磷酸盐化学转化膜微观结构的影响.研究发现由于锌系磷化液中乙醇胺的添加:(1)改变了AZ91D镁合金锌系磷化膜晶体层的微观结构,促进了晶核的形成和晶粒细化,晶簇间隙中晶核的形成对晶体膜层完整性和致密度起着关键作用;(2)对(Zn_3(PO_4)_2·_4H_2O)晶体的取向有影响,有控制晶簇尺寸使磷化结晶组织更均匀的作用;(3)MEA在1.2g/L时磷化膜层平整致密、晶簇的尺寸均匀缺陷最少;(4)锌系磷化膜有两层结构:(Zn_3(PO_4)_2·_4H_2O)晶体外层和非晶态内层;(5)MEA的不同添加量对晶体层孔隙的影响有3种类型:表面浅孔(a型),晶簇间缝隙或微裂纹(b型),开放缺陷(c型).
The effect of the concentration of ethanolamine (MEA) additive on the microstructure of phosphate coating was investigated using X-ray diffraction (XRD), scanning electron microscope (SEM). The results showed that the addition of ethanolamineadditive had several effects on the microstructure of phosphate coating as follows. (1) The addition of ethanolamine additive was propitious to nucleation and grain-refining, which has critical effect on the integrality of the phosphate coating. (2) Ethanolamine additive is influential to the preferential orientation of (Zn_3(PO_4)_2·_4H_2O) crystal, and has an effect on the control of the size of crystal cluster as well as the uniformity of crystal structure. (3) The phosphate coating with the compact surface morphologies and least flaws was obtained when the concentration of ethanolamine additive was 1.2g/L. (4) The phosphate conversion coatings formed a duplex structure: a crystal outer layer and an amorphous inner layer. (5) The different amount of ethanolamine additive resulted three types of hole: the surface of shallow porosity (a), micro flaws between the cracks or micro-cracks (b) and open defects (c).
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