超重力法制备的LDH涂层对镁合金耐蚀性的提升作用

采用超重力法在旋转填充床（RPB）中制备富马酸根与柠檬酸根复配插层的层状双氢氧化物（LDH）浆液，然后进行水热处理，在AZ31镁合金表面生长出富马酸根与柠檬酸根插层的LDH涂层。利用X射线衍射仪（XRD）、傅里叶变换红外光谱仪（FT-IR）对LDH粉末进行表征，利用X射线光电子能谱仪（XPS）对AZ31镁合金表面的LDH涂层进行表征，结果证明成功制备出富马酸根与柠檬酸根插层的LDH涂层。使用场发射扫描电子显微镜（FESEM）观察LDH涂层的外观形貌，通过电化学试验测试了生长LDH涂层的AZ31镁合金的耐腐蚀性能，结果表明，采用超重力法制备的含有富马酸根与柠檬酸根插层的LDH涂层表面生成完整、致密的覆盖层，几乎看不到簇立状的LDH片。与共沉淀法相比，使用超重力法制备的LDH涂层，其动电位极化曲线拟合出的腐蚀电位更大，腐蚀电流密度更小。在3.5% NaCl溶液中浸泡96 h后，采用超重力法制备的含有富马酸根与柠檬酸根插层的LDH涂层的阻抗值R_ct为56.69kΩ·cm²，大于仅浸泡1 h的采用共沉淀法制备的不含富马酸根与柠檬酸根插层的LDH涂层（R_ct为49.45kΩ·cm²），表明超重力法制备的LDH涂层表现出更好的耐腐蚀性。

Improvement effect of LDH coating prepared by the high gravity method on corrosion resistance of magnesium alloy

Slurries of layered double hydroxides (LDH) intercalated with fumarate and citrate anions have been prepared in a rotating packed bed (RPB) using a high gravity method. After hydrothermal treatment, a LDH coating intercalated with fumarate and citrate anions was grown on the surface of AZ31 magnesium alloy. The LDH powder was characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), and the LDH coating on AZ31 magnesium alloy was characterized by X-ray photoelectron spectroscopy (XPS). The results showed that the LDH coating intercalated with fumarate and citrate anions was successfully prepared. The appearance of the LDH coating was observed by field emission scanning electron microscopy (FESEM), and the corrosion resistance of AZ31 magnesium alloy with the LDH coating was measured by electrochemical tests. The results show that a complete and dense covering layer was formed on the metal surface using the LDH coating intercalated with fumarate and citrate anions prepared by the high gravity method, and very few cluster-like LDH sheets were observed. Fitting of the potentiodynamic polarization curve shows that compared with the conventional co-precipitation method, the LDH coating prepared by the high gravity method has larger corrosion potential and smaller corrosion current density. After soaking in 3.5% NaCl solution for 96 h, the impedance value R_ct of LDH coating intercalated with fumarate and citrate anions prepared by the high gravity method is 56.69 kΩ·cm², which is higher than that for an LDH coating without intercalated fumarate and citrate anions prepared by the co-precipitation method after soaking for only 1 h (R_ct is 49.45 kΩ·cm²). The results confirm that the LDH coating prepared by the high gravity method shows better corrosion resistance.