镁合金表面缓蚀剂插层LDHs膜的制备及其自愈合性能研究

Effect of anion exchange on self-healing properties of magnesium-aluminum LDHs film on the magnesium alloys

摘要:

本文通过水热法在AZ31镁合金表面原位合成层状双氢氧化物膜层MgAl-LDHs-NO3，采用阴离子交换反应将钨酸根阴离子（WO42-）和半胱氨酸（Cys）阴离子嵌入LDHs层间，制得MgAl-LDHs-WO4和MgAl-LDHs-Cys。利用X射线衍射（XRD）、扫描电子显微镜（SEM）、能谱仪（EDS）、电化学阻抗测试（EIS）研究了膜层的形貌、结构、耐蚀性和自愈合性能。结果表明，在3.5wt.%NaCl溶液中三种膜层的耐蚀性由大到小依次为LDHs-WO4＞LDHs-Cys＞LDHs-NO3。预制划痕后在3.5wt.%NaCl溶液中浸泡实验表明，三种膜层均表现出良好的自愈合能力，电化学结果显示浸泡8天时耐蚀性最佳，随后呈下降趋势，且LDHs-WO4和LDHs-Cys自愈合能力明显优于LDHs-NO3。这是由于LDHs-WO4和LDHs-Cys含有缓蚀性阴离子，膜层不仅阻隔溶液对基体的腐蚀，而且LDHs的层间结构还可以释放缓蚀性离子，这些离子与镁结合形成难溶沉淀，促进膜层的自愈合过程。

Abstract:

In this paper, a layered double hydroxide film layer MgAl-LDHs-NO3 was synthesized by hydrothermal method. Tungstate anions (WO42-) and Cysteine(Cys) anions were intercalated into the LDHs interlayer by virtue of the anion exchange reaction to acquire MgAl-LDHs-WO4 and MgAl-LDHs-Cys films. X-ray diffraction (XRD), scanning electron microscope (SEM), Energy spectrometer (EDS), and electrochemical impedance test (EIS) were performed to study the morphology, structure, corrosion resistance and self-healing performance. The results showed that the corrosion resistance were in the sequence of LDHs-WO4＞LDHs-Cys＞LDHs-NO3.All of three film were of effectively self-healing ability. Electrochemical results showed that the films induced to the scratch treatment have better corrosion resistance after immersed in 3.5 wt.% NaCl solution for 8 days, and then showed a downward trend. .Compared to MgAl-LDHs, LDHs-WO4 and LDHs-Cys, contained corrosion inhibiting anions, were displayed the better self-healing ability, due to the film layer could not only capture Cl-, but also release corrosion-inhibiting anions.